1 /*
   2  * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package jdk.nashorn.internal.codegen;
  27 
  28 import static jdk.nashorn.internal.codegen.ClassEmitter.Flag.PRIVATE;
  29 import static jdk.nashorn.internal.codegen.ClassEmitter.Flag.STATIC;
  30 import static jdk.nashorn.internal.codegen.CompilerConstants.ARGUMENTS;
  31 import static jdk.nashorn.internal.codegen.CompilerConstants.CALLEE;
  32 import static jdk.nashorn.internal.codegen.CompilerConstants.CREATE_PROGRAM_FUNCTION;
  33 import static jdk.nashorn.internal.codegen.CompilerConstants.GET_MAP;
  34 import static jdk.nashorn.internal.codegen.CompilerConstants.GET_STRING;
  35 import static jdk.nashorn.internal.codegen.CompilerConstants.QUICK_PREFIX;
  36 import static jdk.nashorn.internal.codegen.CompilerConstants.REGEX_PREFIX;
  37 import static jdk.nashorn.internal.codegen.CompilerConstants.RETURN;
  38 import static jdk.nashorn.internal.codegen.CompilerConstants.SCOPE;
  39 import static jdk.nashorn.internal.codegen.CompilerConstants.SPLIT_ARRAY_ARG;
  40 import static jdk.nashorn.internal.codegen.CompilerConstants.SPLIT_PREFIX;
  41 import static jdk.nashorn.internal.codegen.CompilerConstants.THIS;
  42 import static jdk.nashorn.internal.codegen.CompilerConstants.VARARGS;
  43 import static jdk.nashorn.internal.codegen.CompilerConstants.constructorNoLookup;
  44 import static jdk.nashorn.internal.codegen.CompilerConstants.interfaceCallNoLookup;
  45 import static jdk.nashorn.internal.codegen.CompilerConstants.methodDescriptor;
  46 import static jdk.nashorn.internal.codegen.CompilerConstants.staticCallNoLookup;
  47 import static jdk.nashorn.internal.codegen.CompilerConstants.typeDescriptor;
  48 import static jdk.nashorn.internal.codegen.CompilerConstants.virtualCallNoLookup;
  49 import static jdk.nashorn.internal.codegen.ObjectClassGenerator.OBJECT_FIELDS_ONLY;
  50 import static jdk.nashorn.internal.ir.Symbol.HAS_SLOT;
  51 import static jdk.nashorn.internal.ir.Symbol.IS_INTERNAL;
  52 import static jdk.nashorn.internal.runtime.UnwarrantedOptimismException.INVALID_PROGRAM_POINT;
  53 import static jdk.nashorn.internal.runtime.UnwarrantedOptimismException.isValid;
  54 import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_APPLY_TO_CALL;
  55 import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_FAST_SCOPE;
  56 import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_OPTIMISTIC;
  57 import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_PROGRAM_POINT_SHIFT;
  58 import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_SCOPE;
  59 import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_STRICT;
  60 
  61 import java.io.PrintWriter;
  62 import java.util.ArrayDeque;
  63 import java.util.ArrayList;
  64 import java.util.Arrays;
  65 import java.util.BitSet;
  66 import java.util.Collection;
  67 import java.util.Collections;
  68 import java.util.Deque;
  69 import java.util.EnumSet;
  70 import java.util.HashMap;
  71 import java.util.HashSet;
  72 import java.util.Iterator;
  73 import java.util.LinkedList;
  74 import java.util.List;
  75 import java.util.Map;
  76 import java.util.Set;
  77 import java.util.TreeMap;
  78 import java.util.function.Supplier;
  79 import jdk.nashorn.internal.IntDeque;
  80 import jdk.nashorn.internal.codegen.ClassEmitter.Flag;
  81 import jdk.nashorn.internal.codegen.CompilerConstants.Call;
  82 import jdk.nashorn.internal.codegen.types.ArrayType;
  83 import jdk.nashorn.internal.codegen.types.Type;
  84 import jdk.nashorn.internal.ir.AccessNode;
  85 import jdk.nashorn.internal.ir.BaseNode;
  86 import jdk.nashorn.internal.ir.BinaryNode;
  87 import jdk.nashorn.internal.ir.Block;
  88 import jdk.nashorn.internal.ir.BlockStatement;
  89 import jdk.nashorn.internal.ir.BreakNode;
  90 import jdk.nashorn.internal.ir.BreakableNode;
  91 import jdk.nashorn.internal.ir.CallNode;
  92 import jdk.nashorn.internal.ir.CaseNode;
  93 import jdk.nashorn.internal.ir.CatchNode;
  94 import jdk.nashorn.internal.ir.ContinueNode;
  95 import jdk.nashorn.internal.ir.EmptyNode;
  96 import jdk.nashorn.internal.ir.Expression;
  97 import jdk.nashorn.internal.ir.ExpressionStatement;
  98 import jdk.nashorn.internal.ir.ForNode;
  99 import jdk.nashorn.internal.ir.FunctionNode;
 100 import jdk.nashorn.internal.ir.FunctionNode.CompilationState;
 101 import jdk.nashorn.internal.ir.IdentNode;
 102 import jdk.nashorn.internal.ir.IfNode;
 103 import jdk.nashorn.internal.ir.IndexNode;
 104 import jdk.nashorn.internal.ir.JoinPredecessor;
 105 import jdk.nashorn.internal.ir.JoinPredecessorExpression;
 106 import jdk.nashorn.internal.ir.LabelNode;
 107 import jdk.nashorn.internal.ir.LexicalContext;
 108 import jdk.nashorn.internal.ir.LexicalContextNode;
 109 import jdk.nashorn.internal.ir.LiteralNode;
 110 import jdk.nashorn.internal.ir.LiteralNode.ArrayLiteralNode;
 111 import jdk.nashorn.internal.ir.LiteralNode.ArrayLiteralNode.ArrayUnit;
 112 import jdk.nashorn.internal.ir.LiteralNode.PrimitiveLiteralNode;
 113 import jdk.nashorn.internal.ir.LocalVariableConversion;
 114 import jdk.nashorn.internal.ir.LoopNode;
 115 import jdk.nashorn.internal.ir.Node;
 116 import jdk.nashorn.internal.ir.ObjectNode;
 117 import jdk.nashorn.internal.ir.Optimistic;
 118 import jdk.nashorn.internal.ir.PropertyNode;
 119 import jdk.nashorn.internal.ir.ReturnNode;
 120 import jdk.nashorn.internal.ir.RuntimeNode;
 121 import jdk.nashorn.internal.ir.RuntimeNode.Request;
 122 import jdk.nashorn.internal.ir.SplitNode;
 123 import jdk.nashorn.internal.ir.Statement;
 124 import jdk.nashorn.internal.ir.SwitchNode;
 125 import jdk.nashorn.internal.ir.Symbol;
 126 import jdk.nashorn.internal.ir.TernaryNode;
 127 import jdk.nashorn.internal.ir.ThrowNode;
 128 import jdk.nashorn.internal.ir.TryNode;
 129 import jdk.nashorn.internal.ir.UnaryNode;
 130 import jdk.nashorn.internal.ir.VarNode;
 131 import jdk.nashorn.internal.ir.WhileNode;
 132 import jdk.nashorn.internal.ir.WithNode;
 133 import jdk.nashorn.internal.ir.visitor.NodeOperatorVisitor;
 134 import jdk.nashorn.internal.ir.visitor.NodeVisitor;
 135 import jdk.nashorn.internal.objects.Global;
 136 import jdk.nashorn.internal.objects.ScriptFunctionImpl;
 137 import jdk.nashorn.internal.parser.Lexer.RegexToken;
 138 import jdk.nashorn.internal.parser.TokenType;
 139 import jdk.nashorn.internal.runtime.Context;
 140 import jdk.nashorn.internal.runtime.Debug;
 141 import jdk.nashorn.internal.runtime.ECMAException;
 142 import jdk.nashorn.internal.runtime.JSType;
 143 import jdk.nashorn.internal.runtime.OptimisticReturnFilters;
 144 import jdk.nashorn.internal.runtime.PropertyMap;
 145 import jdk.nashorn.internal.runtime.RecompilableScriptFunctionData;
 146 import jdk.nashorn.internal.runtime.RewriteException;
 147 import jdk.nashorn.internal.runtime.Scope;
 148 import jdk.nashorn.internal.runtime.ScriptEnvironment;
 149 import jdk.nashorn.internal.runtime.ScriptFunction;
 150 import jdk.nashorn.internal.runtime.ScriptObject;
 151 import jdk.nashorn.internal.runtime.ScriptRuntime;
 152 import jdk.nashorn.internal.runtime.Source;
 153 import jdk.nashorn.internal.runtime.Undefined;
 154 import jdk.nashorn.internal.runtime.UnwarrantedOptimismException;
 155 import jdk.nashorn.internal.runtime.arrays.ArrayData;
 156 import jdk.nashorn.internal.runtime.linker.LinkerCallSite;
 157 import jdk.nashorn.internal.runtime.logging.DebugLogger;
 158 import jdk.nashorn.internal.runtime.logging.Loggable;
 159 import jdk.nashorn.internal.runtime.logging.Logger;
 160 import jdk.nashorn.internal.runtime.options.Options;
 161 
 162 /**
 163  * This is the lowest tier of the code generator. It takes lowered ASTs emitted
 164  * from Lower and emits Java byte code. The byte code emission logic is broken
 165  * out into MethodEmitter. MethodEmitter works internally with a type stack, and
 166  * keeps track of the contents of the byte code stack. This way we avoid a large
 167  * number of special cases on the form
 168  * <pre>
 169  * if (type == INT) {
 170  *     visitInsn(ILOAD, slot);
 171  * } else if (type == DOUBLE) {
 172  *     visitInsn(DOUBLE, slot);
 173  * }
 174  * </pre>
 175  * This quickly became apparent when the code generator was generalized to work
 176  * with all types, and not just numbers or objects.
 177  * <p>
 178  * The CodeGenerator visits nodes only once, tags them as resolved and emits
 179  * bytecode for them.
 180  */
 181 @Logger(name="codegen")
 182 final class CodeGenerator extends NodeOperatorVisitor<CodeGeneratorLexicalContext> implements Loggable {
 183 
 184     private static final Type SCOPE_TYPE = Type.typeFor(ScriptObject.class);
 185 
 186     private static final String GLOBAL_OBJECT = Type.getInternalName(Global.class);
 187 
 188     private static final String SCRIPTFUNCTION_IMPL_NAME = Type.getInternalName(ScriptFunctionImpl.class);
 189     private static final Type   SCRIPTFUNCTION_IMPL_TYPE   = Type.typeFor(ScriptFunction.class);
 190 
 191     private static final Call CREATE_REWRITE_EXCEPTION = CompilerConstants.staticCallNoLookup(RewriteException.class,
 192             "create", RewriteException.class, UnwarrantedOptimismException.class, Object[].class, String[].class);
 193     private static final Call CREATE_REWRITE_EXCEPTION_REST_OF = CompilerConstants.staticCallNoLookup(RewriteException.class,
 194             "create", RewriteException.class, UnwarrantedOptimismException.class, Object[].class, String[].class, int[].class);
 195 
 196     private static final Call ENSURE_INT = CompilerConstants.staticCallNoLookup(OptimisticReturnFilters.class,
 197             "ensureInt", int.class, Object.class, int.class);
 198     private static final Call ENSURE_LONG = CompilerConstants.staticCallNoLookup(OptimisticReturnFilters.class,
 199             "ensureLong", long.class, Object.class, int.class);
 200     private static final Call ENSURE_NUMBER = CompilerConstants.staticCallNoLookup(OptimisticReturnFilters.class,
 201             "ensureNumber", double.class, Object.class, int.class);
 202 
 203     private static final Class<?> ITERATOR_CLASS = Iterator.class;
 204     static {
 205         assert ITERATOR_CLASS == CompilerConstants.ITERATOR_PREFIX.type();
 206     }
 207     private static final Type ITERATOR_TYPE = Type.typeFor(ITERATOR_CLASS);
 208     private static final Type EXCEPTION_TYPE = Type.typeFor(CompilerConstants.EXCEPTION_PREFIX.type());
 209 
 210     /** Constant data & installation. The only reason the compiler keeps this is because it is assigned
 211      *  by reflection in class installation */
 212     private final Compiler compiler;
 213 
 214     /** Is the current code submitted by 'eval' call? */
 215     private final boolean evalCode;
 216 
 217     /** Call site flags given to the code generator to be used for all generated call sites */
 218     private final int callSiteFlags;
 219 
 220     /** How many regexp fields have been emitted */
 221     private int regexFieldCount;
 222 
 223     /** Line number for last statement. If we encounter a new line number, line number bytecode information
 224      *  needs to be generated */
 225     private int lastLineNumber = -1;
 226 
 227     /** When should we stop caching regexp expressions in fields to limit bytecode size? */
 228     private static final int MAX_REGEX_FIELDS = 2 * 1024;
 229 
 230     /** Current method emitter */
 231     private MethodEmitter method;
 232 
 233     /** Current compile unit */
 234     private CompileUnit unit;
 235 
 236     private final DebugLogger log;
 237 
 238     /** From what size should we use spill instead of fields for JavaScript objects? */
 239     private static final int OBJECT_SPILL_THRESHOLD = Options.getIntProperty("nashorn.spill.threshold", 256);
 240 
 241     private static boolean assertsEnabled = false;
 242     static {
 243         assert assertsEnabled = true; // Intentional side effect
 244     }
 245 
 246     private final Set<String> emittedMethods = new HashSet<>();
 247 
 248     // Function Id -> ContinuationInfo. Used by compilation of rest-of function only.
 249     private final Map<Integer, ContinuationInfo> fnIdToContinuationInfo = new HashMap<>();
 250 
 251     private final Deque<Label> scopeEntryLabels = new ArrayDeque<>();
 252 
 253     private final Set<Integer> initializedFunctionIds = new HashSet<>();
 254 
 255     private static final Label METHOD_BOUNDARY = new Label("");
 256     private final Deque<Label> catchLabels = new ArrayDeque<>();
 257     // Number of live locals on entry to (and thus also break from) labeled blocks.
 258     private final IntDeque labeledBlockBreakLiveLocals = new IntDeque();
 259 
 260     //is this a rest of compilation
 261     private final int[] continuationEntryPoints;
 262 
 263     /**
 264      * Constructor.
 265      *
 266      * @param compiler
 267      */
 268     CodeGenerator(final Compiler compiler, final int[] continuationEntryPoints) {
 269         super(new CodeGeneratorLexicalContext());
 270         this.compiler                = compiler;
 271         this.evalCode                = compiler.getSource().isEvalCode();
 272         this.continuationEntryPoints = continuationEntryPoints;
 273         this.callSiteFlags           = compiler.getScriptEnvironment()._callsite_flags;
 274         this.log                     = initLogger(compiler.getContext());
 275     }
 276 
 277     @Override
 278     public DebugLogger getLogger() {
 279         return log;
 280     }
 281 
 282     @Override
 283     public DebugLogger initLogger(final Context context) {
 284         return context.getLogger(this.getClass());
 285     }
 286 
 287     /**
 288      * Gets the call site flags, adding the strict flag if the current function
 289      * being generated is in strict mode
 290      *
 291      * @return the correct flags for a call site in the current function
 292      */
 293     int getCallSiteFlags() {
 294         return lc.getCurrentFunction().isStrict() ? callSiteFlags | CALLSITE_STRICT : callSiteFlags;
 295     }
 296 
 297     /**
 298      * Are we generating code for 'eval' code?
 299      * @return true if currently compiled code is 'eval' code.
 300      */
 301     boolean isEvalCode() {
 302         return evalCode;
 303     }
 304 
 305     /**
 306      * Load an identity node
 307      *
 308      * @param identNode an identity node to load
 309      * @return the method generator used
 310      */
 311     private MethodEmitter loadIdent(final IdentNode identNode, final TypeBounds resultBounds) {
 312         final Symbol symbol = identNode.getSymbol();
 313 
 314         if (!symbol.isScope()) {
 315             final Type type = identNode.getType();
 316             if(type == Type.UNDEFINED) {
 317                 return method.loadUndefined(Type.OBJECT);
 318             }
 319 
 320             assert symbol.hasSlot() || symbol.isParam();
 321             return method.load(identNode);
 322         }
 323 
 324         assert identNode.getSymbol().isScope() : identNode + " is not in scope!";
 325         final int flags = CALLSITE_SCOPE | getCallSiteFlags();
 326         if (isFastScope(symbol)) {
 327             // Only generate shared scope getter for fast-scope symbols so we know we can dial in correct scope.
 328             if (symbol.getUseCount() > SharedScopeCall.FAST_SCOPE_GET_THRESHOLD && !isOptimisticOrRestOf()) {
 329                 method.loadCompilerConstant(SCOPE);
 330                 // As shared scope vars are only used in non-optimistic compilation, we switch from using TypeBounds to
 331                 // just a single definitive type, resultBounds.widest.
 332                 loadSharedScopeVar(resultBounds.widest, symbol, flags);
 333             } else {
 334                 new LoadFastScopeVar(identNode, resultBounds, flags).emit();
 335             }
 336         } else {
 337             //slow scope load, we have no proto depth
 338             new LoadScopeVar(identNode, resultBounds, flags).emit();
 339         }
 340 
 341         return method;
 342     }
 343 
 344     private boolean isRestOf() {
 345         return continuationEntryPoints != null;
 346     }
 347 
 348     private boolean isOptimisticOrRestOf() {
 349         return useOptimisticTypes() || isRestOf();
 350     }
 351 
 352     private boolean isCurrentContinuationEntryPoint(final int programPoint) {
 353         return isRestOf() && getCurrentContinuationEntryPoint() == programPoint;
 354     }
 355 
 356     private int[] getContinuationEntryPoints() {
 357         return isRestOf() ? continuationEntryPoints : null;
 358     }
 359 
 360     private int getCurrentContinuationEntryPoint() {
 361         return isRestOf() ? continuationEntryPoints[0] : INVALID_PROGRAM_POINT;
 362     }
 363 
 364     private boolean isContinuationEntryPoint(final int programPoint) {
 365         if (isRestOf()) {
 366             assert continuationEntryPoints != null;
 367             for (final int cep : continuationEntryPoints) {
 368                 if (cep == programPoint) {
 369                     return true;
 370                 }
 371             }
 372         }
 373         return false;
 374     }
 375 
 376     /**
 377      * Check if this symbol can be accessed directly with a putfield or getfield or dynamic load
 378      *
 379      * @param symbol symbol to check for fast scope
 380      * @return true if fast scope
 381      */
 382     private boolean isFastScope(final Symbol symbol) {
 383         if (!symbol.isScope()) {
 384             return false;
 385         }
 386 
 387         if (!lc.inDynamicScope()) {
 388             // If there's no with or eval in context, and the symbol is marked as scoped, it is fast scoped. Such a
 389             // symbol must either be global, or its defining block must need scope.
 390             assert symbol.isGlobal() || lc.getDefiningBlock(symbol).needsScope() : symbol.getName();
 391             return true;
 392         }
 393 
 394         if (symbol.isGlobal()) {
 395             // Shortcut: if there's a with or eval in context, globals can't be fast scoped
 396             return false;
 397         }
 398 
 399         // Otherwise, check if there's a dynamic scope between use of the symbol and its definition
 400         final String name = symbol.getName();
 401         boolean previousWasBlock = false;
 402         for (final Iterator<LexicalContextNode> it = lc.getAllNodes(); it.hasNext();) {
 403             final LexicalContextNode node = it.next();
 404             if (node instanceof Block) {
 405                 // If this block defines the symbol, then we can fast scope the symbol.
 406                 final Block block = (Block)node;
 407                 if (block.getExistingSymbol(name) == symbol) {
 408                     assert block.needsScope();
 409                     return true;
 410                 }
 411                 previousWasBlock = true;
 412             } else {
 413                 if (node instanceof WithNode && previousWasBlock || node instanceof FunctionNode && ((FunctionNode)node).needsDynamicScope()) {
 414                     // If we hit a scope that can have symbols introduced into it at run time before finding the defining
 415                     // block, the symbol can't be fast scoped. A WithNode only counts if we've immediately seen a block
 416                     // before - its block. Otherwise, we are currently processing the WithNode's expression, and that's
 417                     // obviously not subjected to introducing new symbols.
 418                     return false;
 419                 }
 420                 previousWasBlock = false;
 421             }
 422         }
 423         // Should've found the symbol defined in a block
 424         throw new AssertionError();
 425     }
 426 
 427     private MethodEmitter loadSharedScopeVar(final Type valueType, final Symbol symbol, final int flags) {
 428         assert !isOptimisticOrRestOf();
 429         if (isFastScope(symbol)) {
 430             method.load(getScopeProtoDepth(lc.getCurrentBlock(), symbol));
 431         } else {
 432             method.load(-1);
 433         }
 434         return lc.getScopeGet(unit, symbol, valueType, flags | CALLSITE_FAST_SCOPE).generateInvoke(method);
 435     }
 436 
 437     private class LoadScopeVar extends OptimisticOperation {
 438         final IdentNode identNode;
 439         private final int flags;
 440 
 441         LoadScopeVar(final IdentNode identNode, final TypeBounds resultBounds, final int flags) {
 442             super(identNode, resultBounds);
 443             this.identNode = identNode;
 444             this.flags = flags;
 445         }
 446 
 447         @Override
 448         void loadStack() {
 449             method.loadCompilerConstant(SCOPE);
 450             getProto();
 451         }
 452 
 453         void getProto() {
 454             //empty
 455         }
 456 
 457         @Override
 458         void consumeStack() {
 459             // If this is either __FILE__, __DIR__, or __LINE__ then load the property initially as Object as we'd convert
 460             // it anyway for replaceLocationPropertyPlaceholder.
 461             if(identNode.isCompileTimePropertyName()) {
 462                 method.dynamicGet(Type.OBJECT, identNode.getSymbol().getName(), flags, identNode.isFunction());
 463                 replaceCompileTimeProperty();
 464             } else {
 465                 dynamicGet(identNode.getSymbol().getName(), flags, identNode.isFunction());
 466             }
 467         }
 468     }
 469 
 470     private class LoadFastScopeVar extends LoadScopeVar {
 471         LoadFastScopeVar(final IdentNode identNode, final TypeBounds resultBounds, final int flags) {
 472             super(identNode, resultBounds, flags | CALLSITE_FAST_SCOPE);
 473         }
 474 
 475         @Override
 476         void getProto() {
 477             loadFastScopeProto(identNode.getSymbol(), false);
 478         }
 479     }
 480 
 481     private MethodEmitter storeFastScopeVar(final Symbol symbol, final int flags) {
 482         loadFastScopeProto(symbol, true);
 483         method.dynamicSet(symbol.getName(), flags | CALLSITE_FAST_SCOPE);
 484         return method;
 485     }
 486 
 487     private int getScopeProtoDepth(final Block startingBlock, final Symbol symbol) {
 488         //walk up the chain from starting block and when we bump into the current function boundary, add the external
 489         //information.
 490         final FunctionNode fn   = lc.getCurrentFunction();
 491         final int          fnId = fn.getId();
 492         final int externalDepth = compiler.getScriptFunctionData(fnId).getExternalSymbolDepth(symbol.getName());
 493 
 494         //count the number of scopes from this place to the start of the function
 495 
 496         final int internalDepth = FindScopeDepths.findInternalDepth(lc, fn, startingBlock, symbol);
 497         final int scopesToStart = FindScopeDepths.findScopesToStart(lc, fn, startingBlock);
 498         int depth = 0;
 499         if (internalDepth == -1) {
 500             depth = scopesToStart + externalDepth;
 501         } else {
 502             assert internalDepth <= scopesToStart;
 503             depth = internalDepth;
 504         }
 505 
 506         return depth;
 507     }
 508 
 509     private void loadFastScopeProto(final Symbol symbol, final boolean swap) {
 510         final int depth = getScopeProtoDepth(lc.getCurrentBlock(), symbol);
 511         assert depth != -1 : "Couldn't find scope depth for symbol " + symbol.getName() + " in " + lc.getCurrentFunction();
 512         if (depth > 0) {
 513             if (swap) {
 514                 method.swap();
 515             }
 516             for (int i = 0; i < depth; i++) {
 517                 method.invoke(ScriptObject.GET_PROTO);
 518             }
 519             if (swap) {
 520                 method.swap();
 521             }
 522         }
 523     }
 524 
 525     /**
 526      * Generate code that loads this node to the stack, not constraining its type
 527      *
 528      * @param expr node to load
 529      *
 530      * @return the method emitter used
 531      */
 532     private MethodEmitter loadExpressionUnbounded(final Expression expr) {
 533         return loadExpression(expr, TypeBounds.UNBOUNDED);
 534     }
 535 
 536     private MethodEmitter loadExpressionAsObject(final Expression expr) {
 537         return loadExpression(expr, TypeBounds.OBJECT);
 538     }
 539 
 540     MethodEmitter loadExpressionAsBoolean(final Expression expr) {
 541         return loadExpression(expr, TypeBounds.BOOLEAN);
 542     }
 543 
 544     // Test whether conversion from source to target involves a call of ES 9.1 ToPrimitive
 545     // with possible side effects from calling an object's toString or valueOf methods.
 546     private static boolean noToPrimitiveConversion(final Type source, final Type target) {
 547         // Object to boolean conversion does not cause ToPrimitive call
 548         return source.isJSPrimitive() || !target.isJSPrimitive() || target.isBoolean();
 549     }
 550 
 551     MethodEmitter loadBinaryOperands(final BinaryNode binaryNode) {
 552         return loadBinaryOperands(binaryNode.lhs(), binaryNode.rhs(), TypeBounds.UNBOUNDED.notWiderThan(binaryNode.getWidestOperandType()), false);
 553     }
 554 
 555     private MethodEmitter loadBinaryOperands(final Expression lhs, final Expression rhs, final TypeBounds explicitOperandBounds, final boolean baseAlreadyOnStack) {
 556         // ECMAScript 5.1 specification (sections 11.5-11.11 and 11.13) prescribes that when evaluating a binary
 557         // expression "LEFT op RIGHT", the order of operations must be: LOAD LEFT, LOAD RIGHT, CONVERT LEFT, CONVERT
 558         // RIGHT, EXECUTE OP. Unfortunately, doing it in this order defeats potential optimizations that arise when we
 559         // can combine a LOAD with a CONVERT operation (e.g. use a dynamic getter with the conversion target type as its
 560         // return value). What we do here is reorder LOAD RIGHT and CONVERT LEFT when possible; it is possible only when
 561         // we can prove that executing CONVERT LEFT can't have a side effect that changes the value of LOAD RIGHT.
 562         // Basically, if we know that either LEFT already is a primitive value, or does not have to be converted to
 563         // a primitive value, or RIGHT is an expression that loads without side effects, then we can do the
 564         // reordering and collapse LOAD/CONVERT into a single operation; otherwise we need to do the more costly
 565         // separate operations to preserve specification semantics.
 566 
 567         // Operands' load type should not be narrower than the narrowest of the individual operand types, nor narrower
 568         // than the lower explicit bound, but it should also not be wider than
 569         final Type narrowestOperandType = Type.narrowest(Type.widest(lhs.getType(), rhs.getType()), explicitOperandBounds.widest);
 570         final TypeBounds operandBounds = explicitOperandBounds.notNarrowerThan(narrowestOperandType);
 571         if (noToPrimitiveConversion(lhs.getType(), explicitOperandBounds.widest) || rhs.isLocal()) {
 572             // Can reorder. Combine load and convert into single operations.
 573             loadExpression(lhs, operandBounds, baseAlreadyOnStack);
 574             loadExpression(rhs, operandBounds, false);
 575         } else {
 576             // Can't reorder. Load and convert separately.
 577             final TypeBounds safeConvertBounds = TypeBounds.UNBOUNDED.notNarrowerThan(narrowestOperandType);
 578             loadExpression(lhs, safeConvertBounds, baseAlreadyOnStack);
 579             loadExpression(rhs, safeConvertBounds, false);
 580             method.swap().convert(operandBounds.within(method.peekType())).swap().convert(operandBounds.within(method.peekType()));
 581         }
 582         assert Type.generic(method.peekType()) == operandBounds.narrowest;
 583         assert Type.generic(method.peekType(1)) == operandBounds.narrowest;
 584 
 585         return method;
 586     }
 587 
 588     private static final class TypeBounds {
 589         final Type narrowest;
 590         final Type widest;
 591 
 592         static final TypeBounds UNBOUNDED = new TypeBounds(Type.UNKNOWN, Type.OBJECT);
 593         static final TypeBounds INT = exact(Type.INT);
 594         static final TypeBounds NUMBER = exact(Type.NUMBER);
 595         static final TypeBounds OBJECT = exact(Type.OBJECT);
 596         static final TypeBounds BOOLEAN = exact(Type.BOOLEAN);
 597 
 598         static TypeBounds exact(final Type type) {
 599             return new TypeBounds(type, type);
 600         }
 601 
 602         TypeBounds(final Type narrowest, final Type widest) {
 603             assert widest    != null && widest    != Type.UNDEFINED && widest != Type.UNKNOWN : widest;
 604             assert narrowest != null && narrowest != Type.UNDEFINED : narrowest;
 605             assert !narrowest.widerThan(widest) : narrowest + " wider than " + widest;
 606             assert !widest.narrowerThan(narrowest);
 607             this.narrowest = Type.generic(narrowest);
 608             this.widest = Type.generic(widest);
 609         }
 610 
 611         TypeBounds notNarrowerThan(final Type type) {
 612             return maybeNew(Type.narrowest(Type.widest(narrowest, type), widest), widest);
 613         }
 614 
 615         TypeBounds notWiderThan(final Type type) {
 616             return maybeNew(Type.narrowest(narrowest, type), Type.narrowest(widest, type));
 617         }
 618 
 619         boolean canBeNarrowerThan(final Type type) {
 620             return narrowest.narrowerThan(type);
 621         }
 622 
 623         TypeBounds maybeNew(final Type newNarrowest, final Type newWidest) {
 624             if(newNarrowest == narrowest && newWidest == widest) {
 625                 return this;
 626             }
 627             return new TypeBounds(newNarrowest, newWidest);
 628         }
 629 
 630         TypeBounds booleanToInt() {
 631             return maybeNew(booleanToInt(narrowest), booleanToInt(widest));
 632         }
 633 
 634         TypeBounds objectToNumber() {
 635             return maybeNew(objectToNumber(narrowest), objectToNumber(widest));
 636         }
 637 
 638         private static Type booleanToInt(final Type t) {
 639             return t == Type.BOOLEAN ? Type.INT : t;
 640         }
 641 
 642         private static Type objectToNumber(final Type t) {
 643             return t.isObject() ? Type.NUMBER : t;
 644         }
 645 
 646         Type within(final Type type) {
 647             if(type.narrowerThan(narrowest)) {
 648                 return narrowest;
 649             }
 650             if(type.widerThan(widest)) {
 651                 return widest;
 652             }
 653             return type;
 654         }
 655 
 656         @Override
 657         public String toString() {
 658             return "[" + narrowest + ", " + widest + "]";
 659         }
 660     }
 661 
 662     MethodEmitter loadExpressionAsType(final Expression expr, final Type type) {
 663         if(type == Type.BOOLEAN) {
 664             return loadExpressionAsBoolean(expr);
 665         } else if(type == Type.UNDEFINED) {
 666             assert expr.getType() == Type.UNDEFINED;
 667             return loadExpressionAsObject(expr);
 668         }
 669         // having no upper bound preserves semantics of optimistic operations in the expression (by not having them
 670         // converted early) and then applies explicit conversion afterwards.
 671         return loadExpression(expr, TypeBounds.UNBOUNDED.notNarrowerThan(type)).convert(type);
 672     }
 673 
 674     private MethodEmitter loadExpression(final Expression expr, final TypeBounds resultBounds) {
 675         return loadExpression(expr, resultBounds, false);
 676     }
 677 
 678     /**
 679      * Emits code for evaluating an expression and leaving its value on top of the stack, narrowing or widening it if
 680      * necessary.
 681      * @param expr the expression to load
 682      * @param resultBounds the incoming type bounds. The value on the top of the stack is guaranteed to not be of narrower
 683      * type than the narrowest bound, or wider type than the widest bound after it is loaded.
 684      * @param baseAlreadyOnStack true if the base of an access or index node is already on the stack. Used to avoid
 685      * double evaluation of bases in self-assignment expressions to access and index nodes. {@code Type.OBJECT} is used
 686      * to indicate the widest possible type.
 687      * @return the method emitter
 688      */
 689     private MethodEmitter loadExpression(final Expression expr, final TypeBounds resultBounds, final boolean baseAlreadyOnStack) {
 690 
 691         /*
 692          * The load may be of type IdentNode, e.g. "x", AccessNode, e.g. "x.y"
 693          * or IndexNode e.g. "x[y]". Both AccessNodes and IndexNodes are
 694          * BaseNodes and the logic for loading the base object is reused
 695          */
 696         final CodeGenerator codegen = this;
 697 
 698         final Node currentDiscard = codegen.lc.getCurrentDiscard();
 699         expr.accept(new NodeOperatorVisitor<LexicalContext>(new LexicalContext()) {
 700             @Override
 701             public boolean enterIdentNode(final IdentNode identNode) {
 702                 loadIdent(identNode, resultBounds);
 703                 return false;
 704             }
 705 
 706             @Override
 707             public boolean enterAccessNode(final AccessNode accessNode) {
 708                 new OptimisticOperation(accessNode, resultBounds) {
 709                     @Override
 710                     void loadStack() {
 711                         if (!baseAlreadyOnStack) {
 712                             loadExpressionAsObject(accessNode.getBase());
 713                         }
 714                         assert method.peekType().isObject();
 715                     }
 716                     @Override
 717                     void consumeStack() {
 718                         final int flags = getCallSiteFlags();
 719                         dynamicGet(accessNode.getProperty(), flags, accessNode.isFunction());
 720                     }
 721                 }.emit(baseAlreadyOnStack ? 1 : 0);
 722                 return false;
 723             }
 724 
 725             @Override
 726             public boolean enterIndexNode(final IndexNode indexNode) {
 727                 new OptimisticOperation(indexNode, resultBounds) {
 728                     @Override
 729                     void loadStack() {
 730                         if (!baseAlreadyOnStack) {
 731                             loadExpressionAsObject(indexNode.getBase());
 732                             loadExpressionUnbounded(indexNode.getIndex());
 733                         }
 734                     }
 735                     @Override
 736                     void consumeStack() {
 737                         final int flags = getCallSiteFlags();
 738                         dynamicGetIndex(flags, indexNode.isFunction());
 739                     }
 740                 }.emit(baseAlreadyOnStack ? 2 : 0);
 741                 return false;
 742             }
 743 
 744             @Override
 745             public boolean enterFunctionNode(final FunctionNode functionNode) {
 746                 // function nodes will always leave a constructed function object on stack, no need to load the symbol
 747                 // separately as in enterDefault()
 748                 lc.pop(functionNode);
 749                 functionNode.accept(codegen);
 750                 // NOTE: functionNode.accept() will produce a different FunctionNode that we discard. This incidentally
 751                 // doesn't cause problems as we're never touching FunctionNode again after it's visited here - codegen
 752                 // is the last element in the compilation pipeline, the AST it produces is not used externally. So, we
 753                 // re-push the original functionNode.
 754                 lc.push(functionNode);
 755                 return false;
 756             }
 757 
 758             @Override
 759             public boolean enterASSIGN(final BinaryNode binaryNode) {
 760                 loadASSIGN(binaryNode);
 761                 return false;
 762             }
 763 
 764             @Override
 765             public boolean enterASSIGN_ADD(final BinaryNode binaryNode) {
 766                 loadASSIGN_ADD(binaryNode);
 767                 return false;
 768             }
 769 
 770             @Override
 771             public boolean enterASSIGN_BIT_AND(final BinaryNode binaryNode) {
 772                 loadASSIGN_BIT_AND(binaryNode);
 773                 return false;
 774             }
 775 
 776             @Override
 777             public boolean enterASSIGN_BIT_OR(final BinaryNode binaryNode) {
 778                 loadASSIGN_BIT_OR(binaryNode);
 779                 return false;
 780             }
 781 
 782             @Override
 783             public boolean enterASSIGN_BIT_XOR(final BinaryNode binaryNode) {
 784                 loadASSIGN_BIT_XOR(binaryNode);
 785                 return false;
 786             }
 787 
 788             @Override
 789             public boolean enterASSIGN_DIV(final BinaryNode binaryNode) {
 790                 loadASSIGN_DIV(binaryNode);
 791                 return false;
 792             }
 793 
 794             @Override
 795             public boolean enterASSIGN_MOD(final BinaryNode binaryNode) {
 796                 loadASSIGN_MOD(binaryNode);
 797                 return false;
 798             }
 799 
 800             @Override
 801             public boolean enterASSIGN_MUL(final BinaryNode binaryNode) {
 802                 loadASSIGN_MUL(binaryNode);
 803                 return false;
 804             }
 805 
 806             @Override
 807             public boolean enterASSIGN_SAR(final BinaryNode binaryNode) {
 808                 loadASSIGN_SAR(binaryNode);
 809                 return false;
 810             }
 811 
 812             @Override
 813             public boolean enterASSIGN_SHL(final BinaryNode binaryNode) {
 814                 loadASSIGN_SHL(binaryNode);
 815                 return false;
 816             }
 817 
 818             @Override
 819             public boolean enterASSIGN_SHR(final BinaryNode binaryNode) {
 820                 loadASSIGN_SHR(binaryNode);
 821                 return false;
 822             }
 823 
 824             @Override
 825             public boolean enterASSIGN_SUB(final BinaryNode binaryNode) {
 826                 loadASSIGN_SUB(binaryNode);
 827                 return false;
 828             }
 829 
 830             @Override
 831             public boolean enterCallNode(final CallNode callNode) {
 832                 return loadCallNode(callNode, resultBounds);
 833             }
 834 
 835             @Override
 836             public boolean enterLiteralNode(final LiteralNode<?> literalNode) {
 837                 loadLiteral(literalNode, resultBounds);
 838                 return false;
 839             }
 840 
 841             @Override
 842             public boolean enterTernaryNode(final TernaryNode ternaryNode) {
 843                 loadTernaryNode(ternaryNode, resultBounds);
 844                 return false;
 845             }
 846 
 847             @Override
 848             public boolean enterADD(final BinaryNode binaryNode) {
 849                 loadADD(binaryNode, resultBounds);
 850                 return false;
 851             }
 852 
 853             @Override
 854             public boolean enterSUB(final UnaryNode unaryNode) {
 855                 loadSUB(unaryNode, resultBounds);
 856                 return false;
 857             }
 858 
 859             @Override
 860             public boolean enterSUB(final BinaryNode binaryNode) {
 861                 loadSUB(binaryNode, resultBounds);
 862                 return false;
 863             }
 864 
 865             @Override
 866             public boolean enterMUL(final BinaryNode binaryNode) {
 867                 loadMUL(binaryNode, resultBounds);
 868                 return false;
 869             }
 870 
 871             @Override
 872             public boolean enterDIV(final BinaryNode binaryNode) {
 873                 loadDIV(binaryNode, resultBounds);
 874                 return false;
 875             }
 876 
 877             @Override
 878             public boolean enterMOD(final BinaryNode binaryNode) {
 879                 loadMOD(binaryNode, resultBounds);
 880                 return false;
 881             }
 882 
 883             @Override
 884             public boolean enterSAR(final BinaryNode binaryNode) {
 885                 loadSAR(binaryNode);
 886                 return false;
 887             }
 888 
 889             @Override
 890             public boolean enterSHL(final BinaryNode binaryNode) {
 891                 loadSHL(binaryNode);
 892                 return false;
 893             }
 894 
 895             @Override
 896             public boolean enterSHR(final BinaryNode binaryNode) {
 897                 loadSHR(binaryNode);
 898                 return false;
 899             }
 900 
 901             @Override
 902             public boolean enterCOMMALEFT(final BinaryNode binaryNode) {
 903                 loadCOMMALEFT(binaryNode, resultBounds);
 904                 return false;
 905             }
 906 
 907             @Override
 908             public boolean enterCOMMARIGHT(final BinaryNode binaryNode) {
 909                 loadCOMMARIGHT(binaryNode, resultBounds);
 910                 return false;
 911             }
 912 
 913             @Override
 914             public boolean enterAND(final BinaryNode binaryNode) {
 915                 loadAND_OR(binaryNode, resultBounds, true);
 916                 return false;
 917             }
 918 
 919             @Override
 920             public boolean enterOR(final BinaryNode binaryNode) {
 921                 loadAND_OR(binaryNode, resultBounds, false);
 922                 return false;
 923             }
 924 
 925             @Override
 926             public boolean enterNOT(final UnaryNode unaryNode) {
 927                 loadNOT(unaryNode);
 928                 return false;
 929             }
 930 
 931             @Override
 932             public boolean enterADD(final UnaryNode unaryNode) {
 933                 loadADD(unaryNode, resultBounds);
 934                 return false;
 935             }
 936 
 937             @Override
 938             public boolean enterBIT_NOT(final UnaryNode unaryNode) {
 939                 loadBIT_NOT(unaryNode);
 940                 return false;
 941             }
 942 
 943             @Override
 944             public boolean enterBIT_AND(final BinaryNode binaryNode) {
 945                 loadBIT_AND(binaryNode);
 946                 return false;
 947             }
 948 
 949             @Override
 950             public boolean enterBIT_OR(final BinaryNode binaryNode) {
 951                 loadBIT_OR(binaryNode);
 952                 return false;
 953             }
 954 
 955             @Override
 956             public boolean enterBIT_XOR(final BinaryNode binaryNode) {
 957                 loadBIT_XOR(binaryNode);
 958                 return false;
 959             }
 960 
 961             @Override
 962             public boolean enterVOID(final UnaryNode unaryNode) {
 963                 loadVOID(unaryNode, resultBounds);
 964                 return false;
 965             }
 966 
 967             @Override
 968             public boolean enterEQ(final BinaryNode binaryNode) {
 969                 loadCmp(binaryNode, Condition.EQ);
 970                 return false;
 971             }
 972 
 973             @Override
 974             public boolean enterEQ_STRICT(final BinaryNode binaryNode) {
 975                 loadCmp(binaryNode, Condition.EQ);
 976                 return false;
 977             }
 978 
 979             @Override
 980             public boolean enterGE(final BinaryNode binaryNode) {
 981                 loadCmp(binaryNode, Condition.GE);
 982                 return false;
 983             }
 984 
 985             @Override
 986             public boolean enterGT(final BinaryNode binaryNode) {
 987                 loadCmp(binaryNode, Condition.GT);
 988                 return false;
 989             }
 990 
 991             @Override
 992             public boolean enterLE(final BinaryNode binaryNode) {
 993                 loadCmp(binaryNode, Condition.LE);
 994                 return false;
 995             }
 996 
 997             @Override
 998             public boolean enterLT(final BinaryNode binaryNode) {
 999                 loadCmp(binaryNode, Condition.LT);
1000                 return false;
1001             }
1002 
1003             @Override
1004             public boolean enterNE(final BinaryNode binaryNode) {
1005                 loadCmp(binaryNode, Condition.NE);
1006                 return false;
1007             }
1008 
1009             @Override
1010             public boolean enterNE_STRICT(final BinaryNode binaryNode) {
1011                 loadCmp(binaryNode, Condition.NE);
1012                 return false;
1013             }
1014 
1015             @Override
1016             public boolean enterObjectNode(final ObjectNode objectNode) {
1017                 loadObjectNode(objectNode);
1018                 return false;
1019             }
1020 
1021             @Override
1022             public boolean enterRuntimeNode(final RuntimeNode runtimeNode) {
1023                 loadRuntimeNode(runtimeNode);
1024                 return false;
1025             }
1026 
1027             @Override
1028             public boolean enterNEW(final UnaryNode unaryNode) {
1029                 loadNEW(unaryNode);
1030                 return false;
1031             }
1032 
1033             @Override
1034             public boolean enterDECINC(final UnaryNode unaryNode) {
1035                 loadDECINC(unaryNode);
1036                 return false;
1037             }
1038 
1039             @Override
1040             public boolean enterJoinPredecessorExpression(final JoinPredecessorExpression joinExpr) {
1041                 loadExpression(joinExpr.getExpression(), resultBounds);
1042                 return false;
1043             }
1044 
1045             @Override
1046             public boolean enterDefault(final Node otherNode) {
1047                 // Must have handled all expressions that can legally be encountered.
1048                 throw new AssertionError(otherNode.getClass().getName());
1049             }
1050         });
1051         if(currentDiscard != expr) {
1052             coerceStackTop(resultBounds);
1053         }
1054         return method;
1055     }
1056 
1057     private MethodEmitter coerceStackTop(final TypeBounds typeBounds) {
1058         return method.convert(typeBounds.within(method.peekType()));
1059     }
1060 
1061     /**
1062      * Closes any still open entries for this block's local variables in the bytecode local variable table.
1063      *
1064      * @param block block containing symbols.
1065      */
1066     private void closeBlockVariables(final Block block) {
1067         for (final Symbol symbol : block.getSymbols()) {
1068             if (symbol.isBytecodeLocal()) {
1069                 method.closeLocalVariable(symbol, block.getBreakLabel());
1070             }
1071         }
1072     }
1073 
1074     @Override
1075     public boolean enterBlock(final Block block) {
1076         method.label(block.getEntryLabel());
1077         if(!method.isReachable()) {
1078             return false;
1079         }
1080         if(lc.isFunctionBody() && emittedMethods.contains(lc.getCurrentFunction().getName())) {
1081             return false;
1082         }
1083         initLocals(block);
1084 
1085         assert lc.getUsedSlotCount() == method.getFirstTemp();
1086         return true;
1087     }
1088 
1089     private boolean useOptimisticTypes() {
1090         return !lc.inSplitNode() && compiler.useOptimisticTypes();
1091     }
1092 
1093     @Override
1094     public Node leaveBlock(final Block block) {
1095         popBlockScope(block);
1096         method.beforeJoinPoint(block);
1097 
1098         closeBlockVariables(block);
1099         lc.releaseSlots();
1100         assert !method.isReachable() || (lc.isFunctionBody() ? 0 : lc.getUsedSlotCount()) == method.getFirstTemp() :
1101             "reachable="+method.isReachable() +
1102             " isFunctionBody=" + lc.isFunctionBody() +
1103             " usedSlotCount=" + lc.getUsedSlotCount() +
1104             " firstTemp=" + method.getFirstTemp();
1105 
1106         return block;
1107     }
1108 
1109     private void popBlockScope(final Block block) {
1110         final Label breakLabel = block.getBreakLabel();
1111 
1112         if(!block.needsScope() || lc.isFunctionBody()) {
1113             emitBlockBreakLabel(breakLabel);
1114             return;
1115         }
1116 
1117         final Label beginTryLabel = scopeEntryLabels.pop();
1118         final Label recoveryLabel = new Label("block_popscope_catch");
1119         emitBlockBreakLabel(breakLabel);
1120         final boolean bodyCanThrow = breakLabel.isAfter(beginTryLabel);
1121         if(bodyCanThrow) {
1122             method._try(beginTryLabel, breakLabel, recoveryLabel);
1123         }
1124 
1125         Label afterCatchLabel = null;
1126 
1127         if(method.isReachable()) {
1128             popScope();
1129             if(bodyCanThrow) {
1130                 afterCatchLabel = new Label("block_after_catch");
1131                 method._goto(afterCatchLabel);
1132             }
1133         }
1134 
1135         if(bodyCanThrow) {
1136             assert !method.isReachable();
1137             method._catch(recoveryLabel);
1138             popScopeException();
1139             method.athrow();
1140         }
1141         if(afterCatchLabel != null) {
1142             method.label(afterCatchLabel);
1143         }
1144     }
1145 
1146     private void emitBlockBreakLabel(final Label breakLabel) {
1147         // TODO: this is totally backwards. Block should not be breakable, LabelNode should be breakable.
1148         final LabelNode labelNode = lc.getCurrentBlockLabelNode();
1149         if(labelNode != null) {
1150             // Only have conversions if we're reachable
1151             assert labelNode.getLocalVariableConversion() == null || method.isReachable();
1152             method.beforeJoinPoint(labelNode);
1153             method.breakLabel(breakLabel, labeledBlockBreakLiveLocals.pop());
1154         } else {
1155             method.label(breakLabel);
1156         }
1157     }
1158 
1159     private void popScope() {
1160         popScopes(1);
1161     }
1162 
1163     /**
1164      * Pop scope as part of an exception handler. Similar to {@code popScope()} but also takes care of adjusting the
1165      * number of scopes that needs to be popped in case a rest-of continuation handler encounters an exception while
1166      * performing a ToPrimitive conversion.
1167      */
1168     private void popScopeException() {
1169         popScope();
1170         final ContinuationInfo ci = getContinuationInfo();
1171         if(ci != null) {
1172             final Label catchLabel = ci.catchLabel;
1173             if(catchLabel != METHOD_BOUNDARY && catchLabel == catchLabels.peek()) {
1174                 ++ci.exceptionScopePops;
1175             }
1176         }
1177     }
1178 
1179     private void popScopesUntil(final LexicalContextNode until) {
1180         popScopes(lc.getScopeNestingLevelTo(until));
1181     }
1182 
1183     private void popScopes(final int count) {
1184         if(count == 0) {
1185             return;
1186         }
1187         assert count > 0; // together with count == 0 check, asserts nonnegative count
1188         if (!method.hasScope()) {
1189             // We can sometimes invoke this method even if the method has no slot for the scope object. Typical example:
1190             // for(;;) { with({}) { break; } }. WithNode normally creates a scope, but if it uses no identifiers and
1191             // nothing else forces creation of a scope in the method, we just won't have the :scope local variable.
1192             return;
1193         }
1194         method.loadCompilerConstant(SCOPE);
1195         for(int i = 0; i < count; ++i) {
1196             method.invoke(ScriptObject.GET_PROTO);
1197         }
1198         method.storeCompilerConstant(SCOPE);
1199     }
1200 
1201     @Override
1202     public boolean enterBreakNode(final BreakNode breakNode) {
1203         if(!method.isReachable()) {
1204             return false;
1205         }
1206         enterStatement(breakNode);
1207 
1208         method.beforeJoinPoint(breakNode);
1209         final BreakableNode breakFrom = lc.getBreakable(breakNode.getLabelName());
1210         popScopesUntil(breakFrom);
1211         final Label breakLabel = breakFrom.getBreakLabel();
1212         breakLabel.markAsBreakTarget();
1213         method.splitAwareGoto(lc, breakLabel, breakFrom);
1214 
1215         return false;
1216     }
1217 
1218     private int loadArgs(final List<Expression> args) {
1219         final int argCount = args.size();
1220         // arg have already been converted to objects here.
1221         if (argCount > LinkerCallSite.ARGLIMIT) {
1222             loadArgsArray(args);
1223             return 1;
1224         }
1225 
1226         for (final Expression arg : args) {
1227             assert arg != null;
1228             loadExpressionUnbounded(arg);
1229         }
1230         return argCount;
1231     }
1232 
1233     private boolean loadCallNode(final CallNode callNode, final TypeBounds resultBounds) {
1234         lineNumber(callNode.getLineNumber());
1235 
1236         final List<Expression> args = callNode.getArgs();
1237         final Expression function = callNode.getFunction();
1238         final Block currentBlock = lc.getCurrentBlock();
1239         final CodeGeneratorLexicalContext codegenLexicalContext = lc;
1240 
1241         function.accept(new NodeVisitor<LexicalContext>(new LexicalContext()) {
1242 
1243             private MethodEmitter sharedScopeCall(final IdentNode identNode, final int flags) {
1244                 final Symbol symbol = identNode.getSymbol();
1245                 final boolean isFastScope = isFastScope(symbol);
1246                 final int scopeCallFlags = flags | (isFastScope ? CALLSITE_FAST_SCOPE : 0);
1247                 new OptimisticOperation(callNode, resultBounds) {
1248                     @Override
1249                     void loadStack() {
1250                         method.loadCompilerConstant(SCOPE);
1251                         if (isFastScope) {
1252                             method.load(getScopeProtoDepth(currentBlock, symbol));
1253                         } else {
1254                             method.load(-1); // Bypass fast-scope code in shared callsite
1255                         }
1256                         loadArgs(args);
1257                     }
1258                     @Override
1259                     void consumeStack() {
1260                         final Type[] paramTypes = method.getTypesFromStack(args.size());
1261                         // We have trouble finding e.g. in Type.typeFor(asm.Type) because it can't see the Context class
1262                         // loader, so we need to weaken reference signatures to Object.
1263                         for(int i = 0; i < paramTypes.length; ++i) {
1264                             paramTypes[i] = Type.generic(paramTypes[i]);
1265                         }
1266                         // As shared scope calls are only used in non-optimistic compilation, we switch from using
1267                         // TypeBounds to just a single definitive type, resultBounds.widest.
1268                         final SharedScopeCall scopeCall = codegenLexicalContext.getScopeCall(unit, symbol,
1269                                 identNode.getType(), resultBounds.widest, paramTypes, scopeCallFlags);
1270                         scopeCall.generateInvoke(method);
1271                     }
1272                 }.emit();
1273                 return method;
1274             }
1275 
1276             private void scopeCall(final IdentNode ident, final int flags) {
1277                 new OptimisticOperation(callNode, resultBounds) {
1278                     int argsCount;
1279                     @Override
1280                     void loadStack() {
1281                         loadExpressionAsObject(ident); // foo() makes no sense if foo == 3
1282                         // ScriptFunction will see CALLSITE_SCOPE and will bind scope accordingly.
1283                         method.loadUndefined(Type.OBJECT); //the 'this'
1284                         argsCount = loadArgs(args);
1285                     }
1286                     @Override
1287                     void consumeStack() {
1288                         dynamicCall(2 + argsCount, flags);
1289                     }
1290                 }.emit();
1291             }
1292 
1293             private void evalCall(final IdentNode ident, final int flags) {
1294                 final Label invoke_direct_eval  = new Label("invoke_direct_eval");
1295                 final Label is_not_eval  = new Label("is_not_eval");
1296                 final Label eval_done = new Label("eval_done");
1297 
1298                 new OptimisticOperation(callNode, resultBounds) {
1299                     int argsCount;
1300                     @Override
1301                     void loadStack() {
1302                         /**
1303                          * We want to load 'eval' to check if it is indeed global builtin eval.
1304                          * If this eval call is inside a 'with' statement, dyn:getMethod|getProp|getElem
1305                          * would be generated if ident is a "isFunction". But, that would result in a
1306                          * bound function from WithObject. We don't want that as bound function as that
1307                          * won't be detected as builtin eval. So, we make ident as "not a function" which
1308                          * results in "dyn:getProp|getElem|getMethod" being generated and so WithObject
1309                          * would return unbounded eval function.
1310                          *
1311                          * Example:
1312                          *
1313                          *  var global = this;
1314                          *  function func() {
1315                          *      with({ eval: global.eval) { eval("var x = 10;") }
1316                          *  }
1317                          */
1318                         loadExpressionAsObject(ident.setIsNotFunction()); // Type.OBJECT as foo() makes no sense if foo == 3
1319                         globalIsEval();
1320                         method.ifeq(is_not_eval);
1321 
1322                         // Load up self (scope).
1323                         method.loadCompilerConstant(SCOPE);
1324                         final List<Expression> evalArgs = callNode.getEvalArgs().getArgs();
1325                         // load evaluated code
1326                         loadExpressionAsObject(evalArgs.get(0));
1327                         // load second and subsequent args for side-effect
1328                         final int numArgs = evalArgs.size();
1329                         for (int i = 1; i < numArgs; i++) {
1330                             loadAndDiscard(evalArgs.get(i));
1331                         }
1332                         method._goto(invoke_direct_eval);
1333 
1334                         method.label(is_not_eval);
1335                         // load this time but with dyn:getMethod|getProp|getElem
1336                         loadExpressionAsObject(ident); // Type.OBJECT as foo() makes no sense if foo == 3
1337                         // This is some scope 'eval' or global eval replaced by user
1338                         // but not the built-in ECMAScript 'eval' function call
1339                         method.loadNull();
1340                         argsCount = loadArgs(callNode.getArgs());
1341                     }
1342 
1343                     @Override
1344                     void consumeStack() {
1345                         // Ordinary call
1346                         dynamicCall(2 + argsCount, flags);
1347                         method._goto(eval_done);
1348 
1349                         method.label(invoke_direct_eval);
1350                         // Special/extra 'eval' arguments. These can be loaded late (in consumeStack) as we know none of
1351                         // them can ever be optimistic.
1352                         method.loadCompilerConstant(THIS);
1353                         method.load(callNode.getEvalArgs().getLocation());
1354                         method.load(CodeGenerator.this.lc.getCurrentFunction().isStrict());
1355                         // direct call to Global.directEval
1356                         globalDirectEval();
1357                         convertOptimisticReturnValue();
1358                         coerceStackTop(resultBounds);
1359                     }
1360                 }.emit();
1361 
1362                 method.label(eval_done);
1363             }
1364 
1365             @Override
1366             public boolean enterIdentNode(final IdentNode node) {
1367                 final Symbol symbol = node.getSymbol();
1368 
1369                 if (symbol.isScope()) {
1370                     final int flags = getCallSiteFlags() | CALLSITE_SCOPE;
1371                     final int useCount = symbol.getUseCount();
1372 
1373                     // Threshold for generating shared scope callsite is lower for fast scope symbols because we know
1374                     // we can dial in the correct scope. However, we also need to enable it for non-fast scopes to
1375                     // support huge scripts like mandreel.js.
1376                     if (callNode.isEval()) {
1377                         evalCall(node, flags);
1378                     } else if (useCount <= SharedScopeCall.FAST_SCOPE_CALL_THRESHOLD
1379                             || !isFastScope(symbol) && useCount <= SharedScopeCall.SLOW_SCOPE_CALL_THRESHOLD
1380                             || CodeGenerator.this.lc.inDynamicScope()
1381                             || isOptimisticOrRestOf()) {
1382                         scopeCall(node, flags);
1383                     } else {
1384                         sharedScopeCall(node, flags);
1385                     }
1386                     assert method.peekType().equals(resultBounds.within(callNode.getType())) : method.peekType() + " != " + resultBounds + "(" + callNode.getType() + ")";
1387                 } else {
1388                     enterDefault(node);
1389                 }
1390 
1391                 return false;
1392             }
1393 
1394             @Override
1395             public boolean enterAccessNode(final AccessNode node) {
1396                 //check if this is an apply to call node. only real applies, that haven't been
1397                 //shadowed from their way to the global scope counts
1398 
1399                 //call nodes have program points.
1400 
1401                 final int flags = getCallSiteFlags() | (callNode.isApplyToCall() ? CALLSITE_APPLY_TO_CALL : 0);
1402 
1403                 new OptimisticOperation(callNode, resultBounds) {
1404                     int argCount;
1405                     @Override
1406                     void loadStack() {
1407                         loadExpressionAsObject(node.getBase());
1408                         method.dup();
1409                         // NOTE: not using a nested OptimisticOperation on this dynamicGet, as we expect to get back
1410                         // a callable object. Nobody in their right mind would optimistically type this call site.
1411                         assert !node.isOptimistic();
1412                         method.dynamicGet(node.getType(), node.getProperty(), flags, true);
1413                         method.swap();
1414                         argCount = loadArgs(args);
1415                     }
1416                     @Override
1417                     void consumeStack() {
1418                         dynamicCall(2 + argCount, flags);
1419                     }
1420                 }.emit();
1421 
1422                 return false;
1423             }
1424 
1425             @Override
1426             public boolean enterFunctionNode(final FunctionNode origCallee) {
1427                 new OptimisticOperation(callNode, resultBounds) {
1428                     FunctionNode callee;
1429                     int argsCount;
1430                     @Override
1431                     void loadStack() {
1432                         callee = (FunctionNode)origCallee.accept(CodeGenerator.this);
1433                         if (callee.isStrict()) { // "this" is undefined
1434                             method.loadUndefined(Type.OBJECT);
1435                         } else { // get global from scope (which is the self)
1436                             globalInstance();
1437                         }
1438                         argsCount = loadArgs(args);
1439                     }
1440 
1441                     @Override
1442                     void consumeStack() {
1443                         final int flags = getCallSiteFlags();
1444                         //assert callNodeType.equals(callee.getReturnType()) : callNodeType + " != " + callee.getReturnType();
1445                         dynamicCall(2 + argsCount, flags);
1446                     }
1447                 }.emit();
1448                 return false;
1449             }
1450 
1451             @Override
1452             public boolean enterIndexNode(final IndexNode node) {
1453                 new OptimisticOperation(callNode, resultBounds) {
1454                     int argsCount;
1455                     @Override
1456                     void loadStack() {
1457                         loadExpressionAsObject(node.getBase());
1458                         method.dup();
1459                         final Type indexType = node.getIndex().getType();
1460                         if (indexType.isObject() || indexType.isBoolean()) {
1461                             loadExpressionAsObject(node.getIndex()); //TODO boolean
1462                         } else {
1463                             loadExpressionUnbounded(node.getIndex());
1464                         }
1465                         // NOTE: not using a nested OptimisticOperation on this dynamicGetIndex, as we expect to get
1466                         // back a callable object. Nobody in their right mind would optimistically type this call site.
1467                         assert !node.isOptimistic();
1468                         method.dynamicGetIndex(node.getType(), getCallSiteFlags(), true);
1469                         method.swap();
1470                         argsCount = loadArgs(args);
1471                     }
1472                     @Override
1473                     void consumeStack() {
1474                         final int flags = getCallSiteFlags();
1475                         dynamicCall(2 + argsCount, flags);
1476                     }
1477                 }.emit();
1478                 return false;
1479             }
1480 
1481             @Override
1482             protected boolean enterDefault(final Node node) {
1483                 new OptimisticOperation(callNode, resultBounds) {
1484                     int argsCount;
1485                     @Override
1486                     void loadStack() {
1487                         // Load up function.
1488                         loadExpressionAsObject(function); //TODO, e.g. booleans can be used as functions
1489                         method.loadUndefined(Type.OBJECT); // ScriptFunction will figure out the correct this when it sees CALLSITE_SCOPE
1490                         argsCount = loadArgs(args);
1491                         }
1492                         @Override
1493                         void consumeStack() {
1494                             final int flags = getCallSiteFlags() | CALLSITE_SCOPE;
1495                             dynamicCall(2 + argsCount, flags);
1496                         }
1497                 }.emit();
1498                 return false;
1499             }
1500         });
1501 
1502         return false;
1503     }
1504 
1505     /**
1506      * Returns the flags with optimistic flag and program point removed.
1507      * @param flags the flags that need optimism stripped from them.
1508      * @return flags without optimism
1509      */
1510     static int nonOptimisticFlags(final int flags) {
1511         return flags & ~(CALLSITE_OPTIMISTIC | -1 << CALLSITE_PROGRAM_POINT_SHIFT);
1512     }
1513 
1514     @Override
1515     public boolean enterContinueNode(final ContinueNode continueNode) {
1516         if(!method.isReachable()) {
1517             return false;
1518         }
1519         enterStatement(continueNode);
1520         method.beforeJoinPoint(continueNode);
1521 
1522         final LoopNode continueTo = lc.getContinueTo(continueNode.getLabelName());
1523         popScopesUntil(continueTo);
1524         final Label continueLabel = continueTo.getContinueLabel();
1525         continueLabel.markAsBreakTarget();
1526         method.splitAwareGoto(lc, continueLabel, continueTo);
1527 
1528         return false;
1529     }
1530 
1531     @Override
1532     public boolean enterEmptyNode(final EmptyNode emptyNode) {
1533         if(!method.isReachable()) {
1534             return false;
1535         }
1536         enterStatement(emptyNode);
1537 
1538         return false;
1539     }
1540 
1541     @Override
1542     public boolean enterExpressionStatement(final ExpressionStatement expressionStatement) {
1543         if(!method.isReachable()) {
1544             return false;
1545         }
1546         enterStatement(expressionStatement);
1547 
1548         loadAndDiscard(expressionStatement.getExpression());
1549         assert method.getStackSize() == 0;
1550 
1551         return false;
1552     }
1553 
1554     @Override
1555     public boolean enterBlockStatement(final BlockStatement blockStatement) {
1556         if(!method.isReachable()) {
1557             return false;
1558         }
1559         enterStatement(blockStatement);
1560 
1561         blockStatement.getBlock().accept(this);
1562 
1563         return false;
1564     }
1565 
1566     @Override
1567     public boolean enterForNode(final ForNode forNode) {
1568         if(!method.isReachable()) {
1569             return false;
1570         }
1571         enterStatement(forNode);
1572         if (forNode.isForIn()) {
1573             enterForIn(forNode);
1574         } else {
1575             final Expression init = forNode.getInit();
1576             if (init != null) {
1577                 loadAndDiscard(init);
1578             }
1579             enterForOrWhile(forNode, forNode.getModify());
1580         }
1581 
1582         return false;
1583     }
1584 
1585     private void enterForIn(final ForNode forNode) {
1586         loadExpression(forNode.getModify(), TypeBounds.OBJECT);
1587         method.invoke(forNode.isForEach() ? ScriptRuntime.TO_VALUE_ITERATOR : ScriptRuntime.TO_PROPERTY_ITERATOR);
1588         final Symbol iterSymbol = forNode.getIterator();
1589         final int iterSlot = iterSymbol.getSlot(Type.OBJECT);
1590         method.store(iterSymbol, ITERATOR_TYPE);
1591 
1592         method.beforeJoinPoint(forNode);
1593 
1594         final Label continueLabel = forNode.getContinueLabel();
1595         final Label breakLabel    = forNode.getBreakLabel();
1596 
1597         method.label(continueLabel);
1598         method.load(ITERATOR_TYPE, iterSlot);
1599         method.invoke(interfaceCallNoLookup(ITERATOR_CLASS, "hasNext", boolean.class));
1600         final JoinPredecessorExpression test = forNode.getTest();
1601         final Block body = forNode.getBody();
1602         if(LocalVariableConversion.hasLiveConversion(test)) {
1603             final Label afterConversion = new Label("for_in_after_test_conv");
1604             method.ifne(afterConversion);
1605             method.beforeJoinPoint(test);
1606             method._goto(breakLabel);
1607             method.label(afterConversion);
1608         } else {
1609             method.ifeq(breakLabel);
1610         }
1611 
1612         new Store<Expression>(forNode.getInit()) {
1613             @Override
1614             protected void storeNonDiscard() {
1615                 // This expression is neither part of a discard, nor needs to be left on the stack after it was
1616                 // stored, so we override storeNonDiscard to be a no-op.
1617             }
1618 
1619             @Override
1620             protected void evaluate() {
1621                 method.load(ITERATOR_TYPE, iterSlot);
1622                 // TODO: optimistic for-in iteration
1623                 method.invoke(interfaceCallNoLookup(ITERATOR_CLASS, "next", Object.class));
1624             }
1625         }.store();
1626         body.accept(this);
1627 
1628         if(method.isReachable()) {
1629             method._goto(continueLabel);
1630         }
1631         method.label(breakLabel);
1632     }
1633 
1634     /**
1635      * Initialize the slots in a frame to undefined.
1636      *
1637      * @param block block with local vars.
1638      */
1639     private void initLocals(final Block block) {
1640         lc.onEnterBlock(block);
1641 
1642         final boolean isFunctionBody = lc.isFunctionBody();
1643         final FunctionNode function = lc.getCurrentFunction();
1644         if (isFunctionBody) {
1645             initializeMethodParameters(function);
1646             if(!function.isVarArg()) {
1647                 expandParameterSlots(function);
1648             }
1649             if (method.hasScope()) {
1650                 if (function.needsParentScope()) {
1651                     method.loadCompilerConstant(CALLEE);
1652                     method.invoke(ScriptFunction.GET_SCOPE);
1653                 } else {
1654                     assert function.hasScopeBlock();
1655                     method.loadNull();
1656                 }
1657                 method.storeCompilerConstant(SCOPE);
1658             }
1659             if (function.needsArguments()) {
1660                 initArguments(function);
1661             }
1662         }
1663 
1664         /*
1665          * Determine if block needs scope, if not, just do initSymbols for this block.
1666          */
1667         if (block.needsScope()) {
1668             /*
1669              * Determine if function is varargs and consequently variables have to
1670              * be in the scope.
1671              */
1672             final boolean varsInScope = function.allVarsInScope();
1673 
1674             // TODO for LET we can do better: if *block* does not contain any eval/with, we don't need its vars in scope.
1675 
1676             final boolean hasArguments = function.needsArguments();
1677             final List<MapTuple<Symbol>> tuples = new ArrayList<>();
1678             final Iterator<IdentNode> paramIter = function.getParameters().iterator();
1679             for (final Symbol symbol : block.getSymbols()) {
1680                 if (symbol.isInternal() || symbol.isThis()) {
1681                     continue;
1682                 }
1683 
1684                 if (symbol.isVar()) {
1685                     assert !varsInScope || symbol.isScope();
1686                     if (varsInScope || symbol.isScope()) {
1687                         assert symbol.isScope()   : "scope for " + symbol + " should have been set in Lower already " + function.getName();
1688                         assert !symbol.hasSlot()  : "slot for " + symbol + " should have been removed in Lower already" + function.getName();
1689 
1690                         //this tuple will not be put fielded, as it has no value, just a symbol
1691                         tuples.add(new MapTuple<Symbol>(symbol.getName(), symbol, null));
1692                     } else {
1693                         assert symbol.hasSlot() || symbol.slotCount() == 0 : symbol + " should have a slot only, no scope";
1694                     }
1695                 } else if (symbol.isParam() && (varsInScope || hasArguments || symbol.isScope())) {
1696                     assert symbol.isScope()   : "scope for " + symbol + " should have been set in AssignSymbols already " + function.getName() + " varsInScope="+varsInScope+" hasArguments="+hasArguments+" symbol.isScope()=" + symbol.isScope();
1697                     assert !(hasArguments && symbol.hasSlot())  : "slot for " + symbol + " should have been removed in Lower already " + function.getName();
1698 
1699                     final Type   paramType;
1700                     final Symbol paramSymbol;
1701 
1702                     if (hasArguments) {
1703                         assert !symbol.hasSlot()  : "slot for " + symbol + " should have been removed in Lower already ";
1704                         paramSymbol = null;
1705                         paramType   = null;
1706                     } else {
1707                         paramSymbol = symbol;
1708                         // NOTE: We're relying on the fact here that Block.symbols is a LinkedHashMap, hence it will
1709                         // return symbols in the order they were defined, and parameters are defined in the same order
1710                         // they appear in the function. That's why we can have a single pass over the parameter list
1711                         // with an iterator, always just scanning forward for the next parameter that matches the symbol
1712                         // name.
1713                         for(;;) {
1714                             final IdentNode nextParam = paramIter.next();
1715                             if(nextParam.getName().equals(symbol.getName())) {
1716                                 paramType = nextParam.getType();
1717                                 break;
1718                             }
1719                         }
1720                     }
1721 
1722                     tuples.add(new MapTuple<Symbol>(symbol.getName(), symbol, paramType, paramSymbol) {
1723                         //this symbol will be put fielded, we can't initialize it as undefined with a known type
1724                         @Override
1725                         public Class<?> getValueType() {
1726                             if (OBJECT_FIELDS_ONLY || value == null || paramType == null) {
1727                                 return Object.class;
1728                             }
1729                             return paramType.isBoolean() ? Object.class : paramType.getTypeClass();
1730                         }
1731                     });
1732                 }
1733             }
1734 
1735             /*
1736              * Create a new object based on the symbols and values, generate
1737              * bootstrap code for object
1738              */
1739             new FieldObjectCreator<Symbol>(this, tuples, true, hasArguments) {
1740                 @Override
1741                 protected void loadValue(final Symbol value, final Type type) {
1742                     method.load(value, type);
1743                 }
1744             }.makeObject(method);
1745             // program function: merge scope into global
1746             if (isFunctionBody && function.isProgram()) {
1747                 method.invoke(ScriptRuntime.MERGE_SCOPE);
1748             }
1749 
1750             method.storeCompilerConstant(SCOPE);
1751             if(!isFunctionBody) {
1752                 // Function body doesn't need a try/catch to restore scope, as it'd be a dead store anyway. Allowing it
1753                 // actually causes issues with UnwarrantedOptimismException handlers as ASM will sort this handler to
1754                 // the top of the exception handler table, so it'll be triggered instead of the UOE handlers.
1755                 final Label scopeEntryLabel = new Label("scope_entry");
1756                 scopeEntryLabels.push(scopeEntryLabel);
1757                 method.label(scopeEntryLabel);
1758             }
1759         } else if (isFunctionBody && function.isVarArg()) {
1760             // Since we don't have a scope, parameters didn't get assigned array indices by the FieldObjectCreator, so
1761             // we need to assign them separately here.
1762             int nextParam = 0;
1763             for (final IdentNode param : function.getParameters()) {
1764                 param.getSymbol().setFieldIndex(nextParam++);
1765             }
1766         }
1767 
1768         // Debugging: print symbols? @see --print-symbols flag
1769         printSymbols(block, (isFunctionBody ? "Function " : "Block in ") + (function.getIdent() == null ? "<anonymous>" : function.getIdent().getName()));
1770     }
1771 
1772     /**
1773      * Incoming method parameters are always declared on method entry; declare them in the local variable table.
1774      * @param function function for which code is being generated.
1775      */
1776     private void initializeMethodParameters(final FunctionNode function) {
1777         final Label functionStart = new Label("fn_start");
1778         method.label(functionStart);
1779         int nextSlot = 0;
1780         if(function.needsCallee()) {
1781             initializeInternalFunctionParameter(CALLEE, function, functionStart, nextSlot++);
1782         }
1783         initializeInternalFunctionParameter(THIS, function, functionStart, nextSlot++);
1784         if(function.isVarArg()) {
1785             initializeInternalFunctionParameter(VARARGS, function, functionStart, nextSlot++);
1786         } else {
1787             for(final IdentNode param: function.getParameters()) {
1788                 final Symbol symbol = param.getSymbol();
1789                 if(symbol.isBytecodeLocal()) {
1790                     method.initializeMethodParameter(symbol, param.getType(), functionStart);
1791                 }
1792             }
1793         }
1794     }
1795 
1796     private void initializeInternalFunctionParameter(final CompilerConstants cc, final FunctionNode fn, final Label functionStart, final int slot) {
1797         final Symbol symbol = initializeInternalFunctionOrSplitParameter(cc, fn, functionStart, slot);
1798         // Internal function params (:callee, this, and :varargs) are never expanded to multiple slots
1799         assert symbol.getFirstSlot() == slot;
1800     }
1801 
1802     private Symbol initializeInternalFunctionOrSplitParameter(final CompilerConstants cc, final FunctionNode fn, final Label functionStart, final int slot) {
1803         final Symbol symbol = fn.getBody().getExistingSymbol(cc.symbolName());
1804         final Type type = Type.typeFor(cc.type());
1805         method.initializeMethodParameter(symbol, type, functionStart);
1806         method.onLocalStore(type, slot);
1807         return symbol;
1808     }
1809 
1810     /**
1811      * Parameters come into the method packed into local variable slots next to each other. Nashorn on the other hand
1812      * can use 1-6 slots for a local variable depending on all the types it needs to store. When this method is invoked,
1813      * the symbols are already allocated such wider slots, but the values are still in tightly packed incoming slots,
1814      * and we need to spread them into their new locations.
1815      * @param function the function for which parameter-spreading code needs to be emitted
1816      */
1817     private void expandParameterSlots(final FunctionNode function) {
1818         final List<IdentNode> parameters = function.getParameters();
1819         // Calculate the total number of incoming parameter slots
1820         int currentIncomingSlot = function.needsCallee() ? 2 : 1;
1821         for(final IdentNode parameter: parameters) {
1822             currentIncomingSlot += parameter.getType().getSlots();
1823         }
1824         // Starting from last parameter going backwards, move the parameter values into their new slots.
1825         for(int i = parameters.size(); i-- > 0;) {
1826             final IdentNode parameter = parameters.get(i);
1827             final Type parameterType = parameter.getType();
1828             final int typeWidth = parameterType.getSlots();
1829             currentIncomingSlot -= typeWidth;
1830             final Symbol symbol = parameter.getSymbol();
1831             final int slotCount = symbol.slotCount();
1832             assert slotCount > 0;
1833             // Scoped parameters must not hold more than one value
1834             assert symbol.isBytecodeLocal() || slotCount == typeWidth;
1835 
1836             // Mark it as having its value stored into it by the method invocation.
1837             method.onLocalStore(parameterType, currentIncomingSlot);
1838             if(currentIncomingSlot != symbol.getSlot(parameterType)) {
1839                 method.load(parameterType, currentIncomingSlot);
1840                 method.store(symbol, parameterType);
1841             }
1842         }
1843     }
1844 
1845     private void initArguments(final FunctionNode function) {
1846         method.loadCompilerConstant(VARARGS);
1847         if (function.needsCallee()) {
1848             method.loadCompilerConstant(CALLEE);
1849         } else {
1850             // If function is strict mode, "arguments.callee" is not populated, so we don't necessarily need the
1851             // caller.
1852             assert function.isStrict();
1853             method.loadNull();
1854         }
1855         method.load(function.getParameters().size());
1856         globalAllocateArguments();
1857         method.storeCompilerConstant(ARGUMENTS);
1858     }
1859 
1860     private boolean skipFunction(final FunctionNode functionNode) {
1861         final ScriptEnvironment env = compiler.getScriptEnvironment();
1862         final boolean lazy = env._lazy_compilation;
1863         final boolean onDemand = compiler.isOnDemandCompilation();
1864 
1865         // If this is on-demand or lazy compilation, don't compile a nested (not topmost) function.
1866         if((onDemand || lazy) && lc.getOutermostFunction() != functionNode) {
1867             return true;
1868         }
1869 
1870         // If lazy compiling with optimistic types, don't compile the program eagerly either. It will soon be
1871         // invalidated anyway. In presence of a class cache, this further means that an obsoleted program version
1872         // lingers around. Also, currently loading previously persisted optimistic types information only works if
1873         // we're on-demand compiling a function, so with this strategy the :program method can also have the warmup
1874         // benefit of using previously persisted types.
1875         // NOTE that this means the first compiled class will effectively just have a :createProgramFunction method, and
1876         // the RecompilableScriptFunctionData (RSFD) object in its constants array. It won't even have the :program
1877         // method. This is by design. It does mean that we're wasting one compiler execution (and we could minimize this
1878         // by just running it up to scope depth calculation, which creates the RSFDs and then this limited codegen).
1879         // We could emit an initial separate compile unit with the initial version of :program in it to better utilize
1880         // the compilation pipeline, but that would need more invasive changes, as currently the assumption that
1881         // :program is emitted into the first compilation unit of the function lives in many places.
1882         if(!onDemand && lazy && env._optimistic_types && functionNode.isProgram()) {
1883             return true;
1884         }
1885 
1886         return false;
1887     }
1888 
1889     @Override
1890     public boolean enterFunctionNode(final FunctionNode functionNode) {
1891         final int fnId = functionNode.getId();
1892 
1893         if (skipFunction(functionNode)) {
1894             // In case we are not generating code for the function, we must create or retrieve the function object and
1895             // load it on the stack here.
1896             newFunctionObject(functionNode, false);
1897             return false;
1898         }
1899 
1900         final String fnName = functionNode.getName();
1901 
1902         // NOTE: we only emit the method for a function with the given name once. We can have multiple functions with
1903         // the same name as a result of inlining finally blocks. However, in the future -- with type specialization,
1904         // notably -- we might need to check for both name *and* signature. Of course, even that might not be
1905         // sufficient; the function might have a code dependency on the type of the variables in its enclosing scopes,
1906         // and the type of such a variable can be different in catch and finally blocks. So, in the future we will have
1907         // to decide to either generate a unique method for each inlined copy of the function, maybe figure out its
1908         // exact type closure and deduplicate based on that, or just decide that functions in finally blocks aren't
1909         // worth it, and generate one method with most generic type closure.
1910         if (!emittedMethods.contains(fnName)) {
1911             log.info("=== BEGIN ", fnName);
1912 
1913             assert functionNode.getCompileUnit() != null : "no compile unit for " + fnName + " " + Debug.id(functionNode);
1914             unit = lc.pushCompileUnit(functionNode.getCompileUnit());
1915             assert lc.hasCompileUnits();
1916 
1917             final ClassEmitter classEmitter = unit.getClassEmitter();
1918             pushMethodEmitter(isRestOf() ? classEmitter.restOfMethod(functionNode) : classEmitter.method(functionNode));
1919             method.setPreventUndefinedLoad();
1920             if(useOptimisticTypes()) {
1921                 lc.pushUnwarrantedOptimismHandlers();
1922             }
1923 
1924             // new method - reset last line number
1925             lastLineNumber = -1;
1926 
1927             method.begin();
1928 
1929             if (isRestOf()) {
1930                 final ContinuationInfo ci = new ContinuationInfo();
1931                 fnIdToContinuationInfo.put(fnId, ci);
1932                 method.gotoLoopStart(ci.getHandlerLabel());
1933             }
1934         }
1935 
1936         return true;
1937     }
1938 
1939     private void pushMethodEmitter(final MethodEmitter newMethod) {
1940         method = lc.pushMethodEmitter(newMethod);
1941         catchLabels.push(METHOD_BOUNDARY);
1942     }
1943 
1944     private void popMethodEmitter() {
1945         method = lc.popMethodEmitter(method);
1946         assert catchLabels.peek() == METHOD_BOUNDARY;
1947         catchLabels.pop();
1948     }
1949 
1950     @Override
1951     public Node leaveFunctionNode(final FunctionNode functionNode) {
1952         try {
1953             final boolean markOptimistic;
1954             if (emittedMethods.add(functionNode.getName())) {
1955                 markOptimistic = generateUnwarrantedOptimismExceptionHandlers(functionNode);
1956                 generateContinuationHandler();
1957                 method.end(); // wrap up this method
1958                 unit   = lc.popCompileUnit(functionNode.getCompileUnit());
1959                 popMethodEmitter();
1960                 log.info("=== END ", functionNode.getName());
1961             } else {
1962                 markOptimistic = false;
1963             }
1964 
1965             FunctionNode newFunctionNode = functionNode.setState(lc, CompilationState.BYTECODE_GENERATED);
1966             if (markOptimistic) {
1967                 newFunctionNode = newFunctionNode.setFlag(lc, FunctionNode.IS_DEOPTIMIZABLE);
1968             }
1969 
1970             newFunctionObject(newFunctionNode, true);
1971             return newFunctionNode;
1972         } catch (final Throwable t) {
1973             Context.printStackTrace(t);
1974             final VerifyError e = new VerifyError("Code generation bug in \"" + functionNode.getName() + "\": likely stack misaligned: " + t + " " + functionNode.getSource().getName());
1975             e.initCause(t);
1976             throw e;
1977         }
1978     }
1979 
1980     @Override
1981     public boolean enterIfNode(final IfNode ifNode) {
1982         if(!method.isReachable()) {
1983             return false;
1984         }
1985         enterStatement(ifNode);
1986 
1987         final Expression test = ifNode.getTest();
1988         final Block pass = ifNode.getPass();
1989         final Block fail = ifNode.getFail();
1990         final boolean hasFailConversion = LocalVariableConversion.hasLiveConversion(ifNode);
1991 
1992         final Label failLabel  = new Label("if_fail");
1993         final Label afterLabel = (fail == null && !hasFailConversion) ? null : new Label("if_done");
1994 
1995         emitBranch(test, failLabel, false);
1996 
1997         pass.accept(this);
1998         if(method.isReachable() && afterLabel != null) {
1999             method._goto(afterLabel); //don't fallthru to fail block
2000         }
2001         method.label(failLabel);
2002 
2003         if (fail != null) {
2004             fail.accept(this);
2005         } else if(hasFailConversion) {
2006             method.beforeJoinPoint(ifNode);
2007         }
2008 
2009         if(afterLabel != null) {
2010             method.label(afterLabel);
2011         }
2012 
2013         return false;
2014     }
2015 
2016     private void emitBranch(final Expression test, final Label label, final boolean jumpWhenTrue) {
2017         new BranchOptimizer(this, method).execute(test, label, jumpWhenTrue);
2018     }
2019 
2020     private void enterStatement(final Statement statement) {
2021         lineNumber(statement);
2022     }
2023 
2024     private void lineNumber(final Statement statement) {
2025         lineNumber(statement.getLineNumber());
2026     }
2027 
2028     private void lineNumber(final int lineNumber) {
2029         if (lineNumber != lastLineNumber) {
2030             method.lineNumber(lineNumber);
2031         }
2032         lastLineNumber = lineNumber;
2033     }
2034 
2035     int getLastLineNumber() {
2036         return lastLineNumber;
2037     }
2038 
2039     /**
2040      * Load a list of nodes as an array of a specific type
2041      * The array will contain the visited nodes.
2042      *
2043      * @param arrayLiteralNode the array of contents
2044      * @param arrayType        the type of the array, e.g. ARRAY_NUMBER or ARRAY_OBJECT
2045      *
2046      * @return the method generator that was used
2047      */
2048     private MethodEmitter loadArray(final ArrayLiteralNode arrayLiteralNode, final ArrayType arrayType) {
2049         assert arrayType == Type.INT_ARRAY || arrayType == Type.LONG_ARRAY || arrayType == Type.NUMBER_ARRAY || arrayType == Type.OBJECT_ARRAY;
2050 
2051         final Expression[]    nodes    = arrayLiteralNode.getValue();
2052         final Object          presets  = arrayLiteralNode.getPresets();
2053         final int[]           postsets = arrayLiteralNode.getPostsets();
2054         final Class<?>        type     = arrayType.getTypeClass();
2055         final List<ArrayUnit> units    = arrayLiteralNode.getUnits();
2056 
2057         loadConstant(presets);
2058 
2059         final Type elementType = arrayType.getElementType();
2060 
2061         if (units != null) {
2062             final MethodEmitter savedMethod     = method;
2063             final FunctionNode  currentFunction = lc.getCurrentFunction();
2064 
2065             for (final ArrayUnit arrayUnit : units) {
2066                 unit = lc.pushCompileUnit(arrayUnit.getCompileUnit());
2067 
2068                 final String className = unit.getUnitClassName();
2069                 assert unit != null;
2070                 final String name      = currentFunction.uniqueName(SPLIT_PREFIX.symbolName());
2071                 final String signature = methodDescriptor(type, ScriptFunction.class, Object.class, ScriptObject.class, type);
2072 
2073                 pushMethodEmitter(unit.getClassEmitter().method(EnumSet.of(Flag.PUBLIC, Flag.STATIC), name, signature));
2074 
2075                 method.setFunctionNode(currentFunction);
2076                 method.begin();
2077 
2078                 defineCommonSplitMethodParameters();
2079                 defineSplitMethodParameter(3, arrayType);
2080 
2081                 fixScopeSlot(currentFunction);
2082 
2083                 lc.enterSplitNode();
2084 
2085                 final int arraySlot = SPLIT_ARRAY_ARG.slot();
2086                 for (int i = arrayUnit.getLo(); i < arrayUnit.getHi(); i++) {
2087                     method.load(arrayType, arraySlot);
2088                     storeElement(nodes, elementType, postsets[i]);
2089                 }
2090 
2091                 method.load(arrayType, arraySlot);
2092                 method._return();
2093                 lc.exitSplitNode();
2094                 method.end();
2095                 lc.releaseSlots();
2096                 popMethodEmitter();
2097 
2098                 assert method == savedMethod;
2099                 method.loadCompilerConstant(CALLEE);
2100                 method.swap();
2101                 method.loadCompilerConstant(THIS);
2102                 method.swap();
2103                 method.loadCompilerConstant(SCOPE);
2104                 method.swap();
2105                 method.invokestatic(className, name, signature);
2106 
2107                 unit = lc.popCompileUnit(unit);
2108             }
2109 
2110             return method;
2111         }
2112 
2113         if(postsets.length > 0) {
2114             final int arraySlot = method.getUsedSlotsWithLiveTemporaries();
2115             method.storeTemp(arrayType, arraySlot);
2116             for (final int postset : postsets) {
2117                 method.load(arrayType, arraySlot);
2118                 storeElement(nodes, elementType, postset);
2119             }
2120             method.load(arrayType, arraySlot);
2121         }
2122         return method;
2123     }
2124 
2125     private void storeElement(final Expression[] nodes, final Type elementType, final int index) {
2126         method.load(index);
2127 
2128         final Expression element = nodes[index];
2129 
2130         if (element == null) {
2131             method.loadEmpty(elementType);
2132         } else {
2133             loadExpressionAsType(element, elementType);
2134         }
2135 
2136         method.arraystore();
2137     }
2138 
2139     private MethodEmitter loadArgsArray(final List<Expression> args) {
2140         final Object[] array = new Object[args.size()];
2141         loadConstant(array);
2142 
2143         for (int i = 0; i < args.size(); i++) {
2144             method.dup();
2145             method.load(i);
2146             loadExpression(args.get(i), TypeBounds.OBJECT); // variable arity methods always take objects
2147             method.arraystore();
2148         }
2149 
2150         return method;
2151     }
2152 
2153     /**
2154      * Load a constant from the constant array. This is only public to be callable from the objects
2155      * subpackage. Do not call directly.
2156      *
2157      * @param string string to load
2158      */
2159     void loadConstant(final String string) {
2160         final String       unitClassName = unit.getUnitClassName();
2161         final ClassEmitter classEmitter  = unit.getClassEmitter();
2162         final int          index         = compiler.getConstantData().add(string);
2163 
2164         method.load(index);
2165         method.invokestatic(unitClassName, GET_STRING.symbolName(), methodDescriptor(String.class, int.class));
2166         classEmitter.needGetConstantMethod(String.class);
2167     }
2168 
2169     /**
2170      * Load a constant from the constant array. This is only public to be callable from the objects
2171      * subpackage. Do not call directly.
2172      *
2173      * @param object object to load
2174      */
2175     void loadConstant(final Object object) {
2176         loadConstant(object, unit, method);
2177     }
2178 
2179     private void loadConstant(final Object object, final CompileUnit compileUnit, final MethodEmitter methodEmitter) {
2180         final String       unitClassName = compileUnit.getUnitClassName();
2181         final ClassEmitter classEmitter  = compileUnit.getClassEmitter();
2182         final int          index         = compiler.getConstantData().add(object);
2183         final Class<?>     cls           = object.getClass();
2184 
2185         if (cls == PropertyMap.class) {
2186             methodEmitter.load(index);
2187             methodEmitter.invokestatic(unitClassName, GET_MAP.symbolName(), methodDescriptor(PropertyMap.class, int.class));
2188             classEmitter.needGetConstantMethod(PropertyMap.class);
2189         } else if (cls.isArray()) {
2190             methodEmitter.load(index);
2191             final String methodName = ClassEmitter.getArrayMethodName(cls);
2192             methodEmitter.invokestatic(unitClassName, methodName, methodDescriptor(cls, int.class));
2193             classEmitter.needGetConstantMethod(cls);
2194         } else {
2195             methodEmitter.loadConstants().load(index).arrayload();
2196             if (object instanceof ArrayData) {
2197                 // avoid cast to non-public ArrayData subclass
2198                 methodEmitter.checkcast(ArrayData.class);
2199                 methodEmitter.invoke(virtualCallNoLookup(ArrayData.class, "copy", ArrayData.class));
2200             } else if (cls != Object.class) {
2201                 methodEmitter.checkcast(cls);
2202             }
2203         }
2204     }
2205 
2206     // literal values
2207     private void loadLiteral(final LiteralNode<?> node, final TypeBounds resultBounds) {
2208         final Object value = node.getValue();
2209 
2210         if (value == null) {
2211             method.loadNull();
2212         } else if (value instanceof Undefined) {
2213             method.loadUndefined(resultBounds.within(Type.OBJECT));
2214         } else if (value instanceof String) {
2215             final String string = (String)value;
2216 
2217             if (string.length() > MethodEmitter.LARGE_STRING_THRESHOLD / 3) { // 3 == max bytes per encoded char
2218                 loadConstant(string);
2219             } else {
2220                 method.load(string);
2221             }
2222         } else if (value instanceof RegexToken) {
2223             loadRegex((RegexToken)value);
2224         } else if (value instanceof Boolean) {
2225             method.load((Boolean)value);
2226         } else if (value instanceof Integer) {
2227             if(!resultBounds.canBeNarrowerThan(Type.OBJECT)) {
2228                 method.load((Integer)value);
2229                 method.convert(Type.OBJECT);
2230             } else if(!resultBounds.canBeNarrowerThan(Type.NUMBER)) {
2231                 method.load(((Integer)value).doubleValue());
2232             } else if(!resultBounds.canBeNarrowerThan(Type.LONG)) {
2233                 method.load(((Integer)value).longValue());
2234             } else {
2235                 method.load((Integer)value);
2236             }
2237         } else if (value instanceof Long) {
2238             if(!resultBounds.canBeNarrowerThan(Type.OBJECT)) {
2239                 method.load((Long)value);
2240                 method.convert(Type.OBJECT);
2241             } else if(!resultBounds.canBeNarrowerThan(Type.NUMBER)) {
2242                 method.load(((Long)value).doubleValue());
2243             } else {
2244                 method.load((Long)value);
2245             }
2246         } else if (value instanceof Double) {
2247             if(!resultBounds.canBeNarrowerThan(Type.OBJECT)) {
2248                 method.load((Double)value);
2249                 method.convert(Type.OBJECT);
2250             } else {
2251                 method.load((Double)value);
2252             }
2253         } else if (node instanceof ArrayLiteralNode) {
2254             final ArrayLiteralNode arrayLiteral = (ArrayLiteralNode)node;
2255             final ArrayType atype = arrayLiteral.getArrayType();
2256             loadArray(arrayLiteral, atype);
2257             globalAllocateArray(atype);
2258         } else {
2259             throw new UnsupportedOperationException("Unknown literal for " + node.getClass() + " " + value.getClass() + " " + value);
2260         }
2261     }
2262 
2263     private MethodEmitter loadRegexToken(final RegexToken value) {
2264         method.load(value.getExpression());
2265         method.load(value.getOptions());
2266         return globalNewRegExp();
2267     }
2268 
2269     private MethodEmitter loadRegex(final RegexToken regexToken) {
2270         if (regexFieldCount > MAX_REGEX_FIELDS) {
2271             return loadRegexToken(regexToken);
2272         }
2273         // emit field
2274         final String       regexName    = lc.getCurrentFunction().uniqueName(REGEX_PREFIX.symbolName());
2275         final ClassEmitter classEmitter = unit.getClassEmitter();
2276 
2277         classEmitter.field(EnumSet.of(PRIVATE, STATIC), regexName, Object.class);
2278         regexFieldCount++;
2279 
2280         // get field, if null create new regex, finally clone regex object
2281         method.getStatic(unit.getUnitClassName(), regexName, typeDescriptor(Object.class));
2282         method.dup();
2283         final Label cachedLabel = new Label("cached");
2284         method.ifnonnull(cachedLabel);
2285 
2286         method.pop();
2287         loadRegexToken(regexToken);
2288         method.dup();
2289         method.putStatic(unit.getUnitClassName(), regexName, typeDescriptor(Object.class));
2290 
2291         method.label(cachedLabel);
2292         globalRegExpCopy();
2293 
2294         return method;
2295     }
2296 
2297     /**
2298      * Check if a property value contains a particular program point
2299      * @param value value
2300      * @param pp    program point
2301      * @return true if it's there.
2302      */
2303     private static boolean propertyValueContains(final Expression value, final int pp) {
2304         return new Supplier<Boolean>() {
2305             boolean contains;
2306 
2307             @Override
2308             public Boolean get() {
2309                 value.accept(new NodeVisitor<LexicalContext>(new LexicalContext()) {
2310                     @Override
2311                     public boolean enterFunctionNode(final FunctionNode functionNode) {
2312                         return false;
2313                     }
2314 
2315                     @Override
2316                     public boolean enterObjectNode(final ObjectNode objectNode) {
2317                         return false;
2318                     }
2319 
2320                     @Override
2321                     public boolean enterDefault(final Node node) {
2322                         if (contains) {
2323                             return false;
2324                         }
2325                         if (node instanceof Optimistic && ((Optimistic)node).getProgramPoint() == pp) {
2326                             contains = true;
2327                             return false;
2328                         }
2329                         return true;
2330                     }
2331                 });
2332 
2333                 return contains;
2334             }
2335         }.get();
2336     }
2337 
2338     private void loadObjectNode(final ObjectNode objectNode) {
2339         final List<PropertyNode> elements = objectNode.getElements();
2340 
2341         final List<MapTuple<Expression>> tuples = new ArrayList<>();
2342         final List<PropertyNode> gettersSetters = new ArrayList<>();
2343         final int ccp = getCurrentContinuationEntryPoint();
2344 
2345         Expression protoNode = null;
2346         boolean restOfProperty = false;
2347 
2348         for (final PropertyNode propertyNode : elements) {
2349             final Expression value = propertyNode.getValue();
2350             final String key = propertyNode.getKeyName();
2351             // Just use a pseudo-symbol. We just need something non null; use the name and zero flags.
2352             final Symbol symbol = value == null ? null : new Symbol(key, 0);
2353 
2354             if (value == null) {
2355                 gettersSetters.add(propertyNode);
2356             } else if (propertyNode.getKey() instanceof IdentNode &&
2357                        key.equals(ScriptObject.PROTO_PROPERTY_NAME)) {
2358                 // ES6 draft compliant __proto__ inside object literal
2359                 // Identifier key and name is __proto__
2360                 protoNode = value;
2361                 continue;
2362             }
2363 
2364             restOfProperty |=
2365                 value != null &&
2366                 isValid(ccp) &&
2367                 propertyValueContains(value, ccp);
2368 
2369             //for literals, a value of null means object type, i.e. the value null or getter setter function
2370             //(I think)
2371             final Class<?> valueType = (OBJECT_FIELDS_ONLY || value == null || value.getType().isBoolean()) ? Object.class : value.getType().getTypeClass();
2372             tuples.add(new MapTuple<Expression>(key, symbol, Type.typeFor(valueType), value) {
2373                 @Override
2374                 public Class<?> getValueType() {
2375                     return type.getTypeClass();
2376                 }
2377             });
2378         }
2379 
2380         final ObjectCreator<?> oc;
2381         if (elements.size() > OBJECT_SPILL_THRESHOLD) {
2382             oc = new SpillObjectCreator(this, tuples);
2383         } else {
2384             oc = new FieldObjectCreator<Expression>(this, tuples) {
2385                 @Override
2386                 protected void loadValue(final Expression node, final Type type) {
2387                     loadExpressionAsType(node, type);
2388                 }};
2389         }
2390         oc.makeObject(method);
2391 
2392         //if this is a rest of method and our continuation point was found as one of the values
2393         //in the properties above, we need to reset the map to oc.getMap() in the continuation
2394         //handler
2395         if (restOfProperty) {
2396             final ContinuationInfo ci = getContinuationInfo();
2397             // Can be set at most once for a single rest-of method
2398             assert ci.getObjectLiteralMap() == null;
2399             ci.setObjectLiteralMap(oc.getMap());
2400             ci.setObjectLiteralStackDepth(method.getStackSize());
2401         }
2402 
2403         method.dup();
2404         if (protoNode != null) {
2405             loadExpressionAsObject(protoNode);
2406             // take care of { __proto__: 34 } or some such!
2407             method.convert(Type.OBJECT);
2408             method.invoke(ScriptObject.SET_PROTO_FROM_LITERAL);
2409         } else {
2410             method.invoke(ScriptObject.SET_GLOBAL_OBJECT_PROTO);
2411         }
2412 
2413         for (final PropertyNode propertyNode : gettersSetters) {
2414             final FunctionNode getter = propertyNode.getGetter();
2415             final FunctionNode setter = propertyNode.getSetter();
2416 
2417             assert getter != null || setter != null;
2418 
2419             method.dup().loadKey(propertyNode.getKey());
2420             if (getter == null) {
2421                 method.loadNull();
2422             } else {
2423                 getter.accept(this);
2424             }
2425 
2426             if (setter == null) {
2427                 method.loadNull();
2428             } else {
2429                 setter.accept(this);
2430             }
2431 
2432             method.invoke(ScriptObject.SET_USER_ACCESSORS);
2433         }
2434     }
2435 
2436     @Override
2437     public boolean enterReturnNode(final ReturnNode returnNode) {
2438         if(!method.isReachable()) {
2439             return false;
2440         }
2441         enterStatement(returnNode);
2442 
2443         method.registerReturn();
2444 
2445         final Type returnType = lc.getCurrentFunction().getReturnType();
2446 
2447         final Expression expression = returnNode.getExpression();
2448         if (expression != null) {
2449             loadExpressionUnbounded(expression);
2450         } else {
2451             method.loadUndefined(returnType);
2452         }
2453 
2454         method._return(returnType);
2455 
2456         return false;
2457     }
2458 
2459     private boolean undefinedCheck(final RuntimeNode runtimeNode, final List<Expression> args) {
2460         final Request request = runtimeNode.getRequest();
2461 
2462         if (!Request.isUndefinedCheck(request)) {
2463             return false;
2464         }
2465 
2466         final Expression lhs = args.get(0);
2467         final Expression rhs = args.get(1);
2468 
2469         final Symbol lhsSymbol = lhs instanceof IdentNode ? ((IdentNode)lhs).getSymbol() : null;
2470         final Symbol rhsSymbol = rhs instanceof IdentNode ? ((IdentNode)rhs).getSymbol() : null;
2471         // One must be a "undefined" identifier, otherwise we can't get here
2472         assert lhsSymbol != null || rhsSymbol != null;
2473 
2474         final Symbol undefinedSymbol;
2475         if (isUndefinedSymbol(lhsSymbol)) {
2476             undefinedSymbol = lhsSymbol;
2477         } else {
2478             assert isUndefinedSymbol(rhsSymbol);
2479             undefinedSymbol = rhsSymbol;
2480         }
2481 
2482         assert undefinedSymbol != null; //remove warning
2483         if (!undefinedSymbol.isScope()) {
2484             return false; //disallow undefined as local var or parameter
2485         }
2486 
2487         if (lhsSymbol == undefinedSymbol && lhs.getType().isPrimitive()) {
2488             //we load the undefined first. never mind, because this will deoptimize anyway
2489             return false;
2490         }
2491 
2492         if(isDeoptimizedExpression(lhs)) {
2493             // This is actually related to "lhs.getType().isPrimitive()" above: any expression being deoptimized in
2494             // the current chain of rest-of compilations used to have a type narrower than Object (so it was primitive).
2495             // We must not perform undefined check specialization for them, as then we'd violate the basic rule of
2496             // "Thou shalt not alter the stack shape between a deoptimized method and any of its (transitive) rest-ofs."
2497             return false;
2498         }
2499 
2500         //make sure that undefined has not been overridden or scoped as a local var
2501         //between us and global
2502         if (!compiler.isGlobalSymbol(lc.getCurrentFunction(), "undefined")) {
2503             return false;
2504         }
2505 
2506         final boolean isUndefinedCheck = request == Request.IS_UNDEFINED;
2507         final Expression expr = undefinedSymbol == lhsSymbol ? rhs : lhs;
2508         if (expr.getType().isPrimitive()) {
2509             loadAndDiscard(expr); //throw away lhs, but it still needs to be evaluated for side effects, even if not in scope, as it can be optimistic
2510             method.load(!isUndefinedCheck);
2511         } else {
2512             final Label checkTrue  = new Label("ud_check_true");
2513             final Label end        = new Label("end");
2514             loadExpressionAsObject(expr);
2515             method.loadUndefined(Type.OBJECT);
2516             method.if_acmpeq(checkTrue);
2517             method.load(!isUndefinedCheck);
2518             method._goto(end);
2519             method.label(checkTrue);
2520             method.load(isUndefinedCheck);
2521             method.label(end);
2522         }
2523 
2524         return true;
2525     }
2526 
2527     private static boolean isUndefinedSymbol(final Symbol symbol) {
2528         return symbol != null && "undefined".equals(symbol.getName());
2529     }
2530 
2531     private static boolean isNullLiteral(final Node node) {
2532         return node instanceof LiteralNode<?> && ((LiteralNode<?>) node).isNull();
2533     }
2534 
2535     private boolean nullCheck(final RuntimeNode runtimeNode, final List<Expression> args) {
2536         final Request request = runtimeNode.getRequest();
2537 
2538         if (!Request.isEQ(request) && !Request.isNE(request)) {
2539             return false;
2540         }
2541 
2542         assert args.size() == 2 : "EQ or NE or TYPEOF need two args";
2543 
2544         Expression lhs = args.get(0);
2545         Expression rhs = args.get(1);
2546 
2547         if (isNullLiteral(lhs)) {
2548             final Expression tmp = lhs;
2549             lhs = rhs;
2550             rhs = tmp;
2551         }
2552 
2553         if (!isNullLiteral(rhs)) {
2554             return false;
2555         }
2556 
2557         if (!lhs.getType().isObject()) {
2558             return false;
2559         }
2560 
2561         if(isDeoptimizedExpression(lhs)) {
2562             // This is actually related to "!lhs.getType().isObject()" above: any expression being deoptimized in
2563             // the current chain of rest-of compilations used to have a type narrower than Object. We must not
2564             // perform null check specialization for them, as then we'd no longer be loading aconst_null on stack
2565             // and thus violate the basic rule of "Thou shalt not alter the stack shape between a deoptimized
2566             // method and any of its (transitive) rest-ofs."
2567             // NOTE also that if we had a representation for well-known constants (e.g. null, 0, 1, -1, etc.) in
2568             // Label$Stack.localLoads then this wouldn't be an issue, as we would never (somewhat ridiculously)
2569             // allocate a temporary local to hold the result of aconst_null before attempting an optimistic
2570             // operation.
2571             return false;
2572         }
2573 
2574         // this is a null literal check, so if there is implicit coercion
2575         // involved like {D}x=null, we will fail - this is very rare
2576         final Label trueLabel  = new Label("trueLabel");
2577         final Label falseLabel = new Label("falseLabel");
2578         final Label endLabel   = new Label("end");
2579 
2580         loadExpressionUnbounded(lhs);    //lhs
2581         final Label popLabel;
2582         if (!Request.isStrict(request)) {
2583             method.dup(); //lhs lhs
2584             popLabel = new Label("pop");
2585         } else {
2586             popLabel = null;
2587         }
2588 
2589         if (Request.isEQ(request)) {
2590             method.ifnull(!Request.isStrict(request) ? popLabel : trueLabel);
2591             if (!Request.isStrict(request)) {
2592                 method.loadUndefined(Type.OBJECT);
2593                 method.if_acmpeq(trueLabel);
2594             }
2595             method.label(falseLabel);
2596             method.load(false);
2597             method._goto(endLabel);
2598             if (!Request.isStrict(request)) {
2599                 method.label(popLabel);
2600                 method.pop();
2601             }
2602             method.label(trueLabel);
2603             method.load(true);
2604             method.label(endLabel);
2605         } else if (Request.isNE(request)) {
2606             method.ifnull(!Request.isStrict(request) ? popLabel : falseLabel);
2607             if (!Request.isStrict(request)) {
2608                 method.loadUndefined(Type.OBJECT);
2609                 method.if_acmpeq(falseLabel);
2610             }
2611             method.label(trueLabel);
2612             method.load(true);
2613             method._goto(endLabel);
2614             if (!Request.isStrict(request)) {
2615                 method.label(popLabel);
2616                 method.pop();
2617             }
2618             method.label(falseLabel);
2619             method.load(false);
2620             method.label(endLabel);
2621         }
2622 
2623         assert runtimeNode.getType().isBoolean();
2624         method.convert(runtimeNode.getType());
2625 
2626         return true;
2627     }
2628 
2629     /**
2630      * Was this expression or any of its subexpressions deoptimized in the current recompilation chain of rest-of methods?
2631      * @param rootExpr the expression being tested
2632      * @return true if the expression or any of its subexpressions was deoptimized in the current recompilation chain.
2633      */
2634     private boolean isDeoptimizedExpression(final Expression rootExpr) {
2635         if(!isRestOf()) {
2636             return false;
2637         }
2638         return new Supplier<Boolean>() {
2639             boolean contains;
2640             @Override
2641             public Boolean get() {
2642                 rootExpr.accept(new NodeVisitor<LexicalContext>(new LexicalContext()) {
2643                     @Override
2644                     public boolean enterFunctionNode(final FunctionNode functionNode) {
2645                         return false;
2646                     }
2647                     @Override
2648                     public boolean enterDefault(final Node node) {
2649                         if(!contains && node instanceof Optimistic) {
2650                             final int pp = ((Optimistic)node).getProgramPoint();
2651                             contains = isValid(pp) && isContinuationEntryPoint(pp);
2652                         }
2653                         return !contains;
2654                     }
2655                 });
2656                 return contains;
2657             }
2658         }.get();
2659     }
2660 
2661     private void loadRuntimeNode(final RuntimeNode runtimeNode) {
2662         final List<Expression> args = new ArrayList<>(runtimeNode.getArgs());
2663         if (nullCheck(runtimeNode, args)) {
2664            return;
2665         } else if(undefinedCheck(runtimeNode, args)) {
2666             return;
2667         }
2668         // Revert a false undefined check to a strict equality check
2669         final RuntimeNode newRuntimeNode;
2670         final Request request = runtimeNode.getRequest();
2671         if (Request.isUndefinedCheck(request)) {
2672             newRuntimeNode = runtimeNode.setRequest(request == Request.IS_UNDEFINED ? Request.EQ_STRICT : Request.NE_STRICT);
2673         } else {
2674             newRuntimeNode = runtimeNode;
2675         }
2676 
2677         new OptimisticOperation(newRuntimeNode, TypeBounds.UNBOUNDED) {
2678             @Override
2679             void loadStack() {
2680                 for (final Expression arg : args) {
2681                     loadExpression(arg, TypeBounds.OBJECT);
2682                 }
2683             }
2684             @Override
2685             void consumeStack() {
2686                 method.invokestatic(
2687                         CompilerConstants.className(ScriptRuntime.class),
2688                         newRuntimeNode.getRequest().toString(),
2689                         new FunctionSignature(
2690                             false,
2691                             false,
2692                             newRuntimeNode.getType(),
2693                             args.size()).toString());
2694             }
2695         }.emit();
2696 
2697         method.convert(newRuntimeNode.getType());
2698     }
2699 
2700     @Override
2701     public boolean enterSplitNode(final SplitNode splitNode) {
2702         if(!method.isReachable()) {
2703             return false;
2704         }
2705 
2706         final CompileUnit splitCompileUnit = splitNode.getCompileUnit();
2707 
2708         final FunctionNode fn   = lc.getCurrentFunction();
2709         final String className  = splitCompileUnit.getUnitClassName();
2710         final String name       = splitNode.getName();
2711 
2712         final Type returnType = fn.getReturnType();
2713 
2714         final Class<?>   rtype          = fn.getReturnType().getTypeClass();
2715         final boolean    needsArguments = fn.needsArguments();
2716         final Class<?>[] ptypes         = needsArguments ?
2717                 new Class<?>[] {ScriptFunction.class, Object.class, ScriptObject.class, ScriptObject.class} :
2718                 new Class<?>[] {ScriptFunction.class, Object.class, ScriptObject.class};
2719 
2720         final MethodEmitter caller = method;
2721         unit = lc.pushCompileUnit(splitCompileUnit);
2722 
2723         final Call splitCall = staticCallNoLookup(
2724             className,
2725             name,
2726             methodDescriptor(rtype, ptypes));
2727 
2728         final MethodEmitter splitEmitter =
2729                 splitCompileUnit.getClassEmitter().method(
2730                         splitNode,
2731                         name,
2732                         rtype,
2733                         ptypes);
2734 
2735         pushMethodEmitter(splitEmitter);
2736         method.setFunctionNode(fn);
2737 
2738         assert fn.needsCallee() : "split function should require callee";
2739         caller.loadCompilerConstant(CALLEE);
2740         caller.loadCompilerConstant(THIS);
2741         caller.loadCompilerConstant(SCOPE);
2742         if (needsArguments) {
2743             caller.loadCompilerConstant(ARGUMENTS);
2744         }
2745         caller.invoke(splitCall);
2746         caller.storeCompilerConstant(RETURN, returnType);
2747 
2748         method.begin();
2749 
2750         defineCommonSplitMethodParameters();
2751         if(needsArguments) {
2752             defineSplitMethodParameter(3, ARGUMENTS);
2753         }
2754 
2755         // Copy scope to its target slot as first thing because the original slot could be used by return symbol.
2756         fixScopeSlot(fn);
2757 
2758         final int returnSlot = fn.compilerConstant(RETURN).getSlot(returnType);
2759         method.defineBlockLocalVariable(returnSlot, returnSlot + returnType.getSlots());
2760         method.loadUndefined(returnType);
2761         method.storeCompilerConstant(RETURN, returnType);
2762 
2763         lc.enterSplitNode();
2764         return true;
2765     }
2766 
2767     private void defineCommonSplitMethodParameters() {
2768         defineSplitMethodParameter(0, CALLEE);
2769         defineSplitMethodParameter(1, THIS);
2770         defineSplitMethodParameter(2, SCOPE);
2771     }
2772 
2773     private void defineSplitMethodParameter(final int slot, final CompilerConstants cc) {
2774         defineSplitMethodParameter(slot, Type.typeFor(cc.type()));
2775     }
2776 
2777     private void defineSplitMethodParameter(final int slot, final Type type) {
2778         method.defineBlockLocalVariable(slot, slot + type.getSlots());
2779         method.onLocalStore(type, slot);
2780     }
2781 
2782     private void fixScopeSlot(final FunctionNode functionNode) {
2783         // TODO hack to move the scope to the expected slot (needed because split methods reuse the same slots as the root method)
2784         final int actualScopeSlot = functionNode.compilerConstant(SCOPE).getSlot(SCOPE_TYPE);
2785         final int defaultScopeSlot = SCOPE.slot();
2786         if (actualScopeSlot != defaultScopeSlot) {
2787             method.defineBlockLocalVariable(actualScopeSlot, actualScopeSlot + 1);
2788             method.load(SCOPE_TYPE, defaultScopeSlot);
2789             method.storeCompilerConstant(SCOPE);
2790         }
2791     }
2792 
2793     @Override
2794     public Node leaveSplitNode(final SplitNode splitNode) {
2795         assert method instanceof SplitMethodEmitter;
2796         lc.exitSplitNode();
2797         final boolean hasReturn = method.hasReturn();
2798         final SplitMethodEmitter splitMethod = ((SplitMethodEmitter)method);
2799         final List<Label> targets = splitMethod.getExternalTargets();
2800         final List<BreakableNode> targetNodes  = splitMethod.getExternalTargetNodes();
2801         final Type returnType = lc.getCurrentFunction().getReturnType();
2802 
2803         try {
2804             // Wrap up this method.
2805 
2806             if(method.isReachable()) {
2807                 method.loadCompilerConstant(RETURN, returnType);
2808                 method._return(returnType);
2809             }
2810             method.end();
2811 
2812             lc.releaseSlots();
2813 
2814             unit   = lc.popCompileUnit(splitNode.getCompileUnit());
2815             popMethodEmitter();
2816 
2817         } catch (final Throwable t) {
2818             Context.printStackTrace(t);
2819             final VerifyError e = new VerifyError("Code generation bug in \"" + splitNode.getName() + "\": likely stack misaligned: " + t + " " + getCurrentSource().getName());
2820             e.initCause(t);
2821             throw e;
2822         }
2823 
2824         // Handle return from split method if there was one.
2825         final MethodEmitter caller = method;
2826         final int     targetCount = targets.size();
2827 
2828         //no external jump targets or return in switch node
2829         if (!hasReturn && targets.isEmpty()) {
2830             return splitNode;
2831         }
2832 
2833         caller.loadCompilerConstant(SCOPE);
2834         caller.checkcast(Scope.class);
2835         caller.invoke(Scope.GET_SPLIT_STATE);
2836 
2837         final Label breakLabel = new Label("no_split_state");
2838         // Split state is -1 for no split state, 0 for return, 1..n+1 for break/continue
2839 
2840         //the common case is that we don't need a switch
2841         if (targetCount == 0) {
2842             assert hasReturn;
2843             caller.ifne(breakLabel);
2844             //has to be zero
2845             caller.label(new Label("split_return"));
2846             caller.loadCompilerConstant(RETURN, returnType);
2847             caller._return(returnType);
2848             caller.label(breakLabel);
2849         } else {
2850             assert !targets.isEmpty();
2851 
2852             final int     low         = hasReturn ? 0 : 1;
2853             final int     labelCount  = targetCount + 1 - low;
2854             final Label[] labels      = new Label[labelCount];
2855 
2856             for (int i = 0; i < labelCount; i++) {
2857                 labels[i] = new Label(i == 0 ? "split_return" : "split_" + targets.get(i - 1));
2858             }
2859             caller.tableswitch(low, targetCount, breakLabel, labels);
2860             for (int i = low; i <= targetCount; i++) {
2861                 caller.label(labels[i - low]);
2862                 if (i == 0) {
2863                     caller.loadCompilerConstant(RETURN, returnType);
2864                     caller._return(returnType);
2865                 } else {
2866                     // Clear split state.
2867                     caller.loadCompilerConstant(SCOPE);
2868                     caller.checkcast(Scope.class);
2869                     caller.load(-1);
2870                     caller.invoke(Scope.SET_SPLIT_STATE);
2871                     final BreakableNode targetNode = targetNodes.get(i - 1);
2872                     final Label label = targets.get(i - 1);
2873                     final JoinPredecessor jumpOrigin = splitNode.getJumpOrigin(label);
2874                     if(jumpOrigin != null) {
2875                         method.beforeJoinPoint(jumpOrigin);
2876                     }
2877                     popScopesUntil(targetNode);
2878                     caller.splitAwareGoto(lc, targets.get(i - 1), targetNode);
2879                 }
2880             }
2881             caller.label(breakLabel);
2882         }
2883 
2884         // If split has a return and caller is itself a split method it needs to propagate the return.
2885         if (hasReturn) {
2886             caller.setHasReturn();
2887         }
2888 
2889         return splitNode;
2890     }
2891 
2892     @Override
2893     public boolean enterSwitchNode(final SwitchNode switchNode) {
2894         if(!method.isReachable()) {
2895             return false;
2896         }
2897         enterStatement(switchNode);
2898 
2899         final Expression     expression  = switchNode.getExpression();
2900         final List<CaseNode> cases       = switchNode.getCases();
2901 
2902         if (cases.isEmpty()) {
2903             // still evaluate expression for side-effects.
2904             loadAndDiscard(expression);
2905             return false;
2906         }
2907 
2908         final CaseNode defaultCase       = switchNode.getDefaultCase();
2909         final Label    breakLabel        = switchNode.getBreakLabel();
2910         final int      liveLocalsOnBreak = method.getUsedSlotsWithLiveTemporaries();
2911 
2912         if (defaultCase != null && cases.size() == 1) {
2913             // default case only
2914             assert cases.get(0) == defaultCase;
2915             loadAndDiscard(expression);
2916             defaultCase.getBody().accept(this);
2917             method.breakLabel(breakLabel, liveLocalsOnBreak);
2918             return false;
2919         }
2920 
2921         // NOTE: it can still change in the tableswitch/lookupswitch case if there's no default case
2922         // but we need to add a synthetic default case for local variable conversions
2923         Label defaultLabel = defaultCase != null ? defaultCase.getEntry() : breakLabel;
2924         final boolean hasSkipConversion = LocalVariableConversion.hasLiveConversion(switchNode);
2925 
2926         if (switchNode.isInteger()) {
2927             // Tree for sorting values.
2928             final TreeMap<Integer, Label> tree = new TreeMap<>();
2929 
2930             // Build up sorted tree.
2931             for (final CaseNode caseNode : cases) {
2932                 final Node test = caseNode.getTest();
2933 
2934                 if (test != null) {
2935                     final Integer value = (Integer)((LiteralNode<?>)test).getValue();
2936                     final Label   entry = caseNode.getEntry();
2937 
2938                     // Take first duplicate.
2939                     if (!tree.containsKey(value)) {
2940                         tree.put(value, entry);
2941                     }
2942                 }
2943             }
2944 
2945             // Copy values and labels to arrays.
2946             final int       size   = tree.size();
2947             final Integer[] values = tree.keySet().toArray(new Integer[size]);
2948             final Label[]   labels = tree.values().toArray(new Label[size]);
2949 
2950             // Discern low, high and range.
2951             final int lo    = values[0];
2952             final int hi    = values[size - 1];
2953             final long range = (long)hi - (long)lo + 1;
2954 
2955             // Find an unused value for default.
2956             int deflt = Integer.MIN_VALUE;
2957             for (final int value : values) {
2958                 if (deflt == value) {
2959                     deflt++;
2960                 } else if (deflt < value) {
2961                     break;
2962                 }
2963             }
2964 
2965             // Load switch expression.
2966             loadExpressionUnbounded(expression);
2967             final Type type = expression.getType();
2968 
2969             // If expression not int see if we can convert, if not use deflt to trigger default.
2970             if (!type.isInteger()) {
2971                 method.load(deflt);
2972                 final Class<?> exprClass = type.getTypeClass();
2973                 method.invoke(staticCallNoLookup(ScriptRuntime.class, "switchTagAsInt", int.class, exprClass.isPrimitive()? exprClass : Object.class, int.class));
2974             }
2975 
2976             if(hasSkipConversion) {
2977                 assert defaultLabel == breakLabel;
2978                 defaultLabel = new Label("switch_skip");
2979             }
2980             // TABLESWITCH needs (range + 3) 32-bit values; LOOKUPSWITCH needs ((size * 2) + 2). Choose the one with
2981             // smaller representation, favor TABLESWITCH when they're equal size.
2982             if (range + 1 <= (size * 2) && range <= Integer.MAX_VALUE) {
2983                 final Label[] table = new Label[(int)range];
2984                 Arrays.fill(table, defaultLabel);
2985                 for (int i = 0; i < size; i++) {
2986                     final int value = values[i];
2987                     table[value - lo] = labels[i];
2988                 }
2989 
2990                 method.tableswitch(lo, hi, defaultLabel, table);
2991             } else {
2992                 final int[] ints = new int[size];
2993                 for (int i = 0; i < size; i++) {
2994                     ints[i] = values[i];
2995                 }
2996 
2997                 method.lookupswitch(defaultLabel, ints, labels);
2998             }
2999             // This is a synthetic "default case" used in absence of actual default case, created if we need to apply
3000             // local variable conversions if neither case is taken.
3001             if(hasSkipConversion) {
3002                 method.label(defaultLabel);
3003                 method.beforeJoinPoint(switchNode);
3004                 method._goto(breakLabel);
3005             }
3006         } else {
3007             final Symbol tagSymbol = switchNode.getTag();
3008             // TODO: we could have non-object tag
3009             final int tagSlot = tagSymbol.getSlot(Type.OBJECT);
3010             loadExpressionAsObject(expression);
3011             method.store(tagSymbol, Type.OBJECT);
3012 
3013             for (final CaseNode caseNode : cases) {
3014                 final Expression test = caseNode.getTest();
3015 
3016                 if (test != null) {
3017                     method.load(Type.OBJECT, tagSlot);
3018                     loadExpressionAsObject(test);
3019                     method.invoke(ScriptRuntime.EQ_STRICT);
3020                     method.ifne(caseNode.getEntry());
3021                 }
3022             }
3023 
3024             if (defaultCase != null) {
3025                 method._goto(defaultLabel);
3026             } else {
3027                 method.beforeJoinPoint(switchNode);
3028                 method._goto(breakLabel);
3029             }
3030         }
3031 
3032         // First case is only reachable through jump
3033         assert !method.isReachable();
3034 
3035         for (final CaseNode caseNode : cases) {
3036             final Label fallThroughLabel;
3037             if(caseNode.getLocalVariableConversion() != null && method.isReachable()) {
3038                 fallThroughLabel = new Label("fallthrough");
3039                 method._goto(fallThroughLabel);
3040             } else {
3041                 fallThroughLabel = null;
3042             }
3043             method.label(caseNode.getEntry());
3044             method.beforeJoinPoint(caseNode);
3045             if(fallThroughLabel != null) {
3046                 method.label(fallThroughLabel);
3047             }
3048             caseNode.getBody().accept(this);
3049         }
3050 
3051         method.breakLabel(breakLabel, liveLocalsOnBreak);
3052 
3053         return false;
3054     }
3055 
3056     @Override
3057     public boolean enterThrowNode(final ThrowNode throwNode) {
3058         if(!method.isReachable()) {
3059             return false;
3060         }
3061         enterStatement(throwNode);
3062 
3063         if (throwNode.isSyntheticRethrow()) {
3064             method.beforeJoinPoint(throwNode);
3065 
3066             //do not wrap whatever this is in an ecma exception, just rethrow it
3067             final IdentNode exceptionExpr = (IdentNode)throwNode.getExpression();
3068             final Symbol exceptionSymbol = exceptionExpr.getSymbol();
3069             method.load(exceptionSymbol, EXCEPTION_TYPE);
3070             method.checkcast(EXCEPTION_TYPE.getTypeClass());
3071             method.athrow();
3072             return false;
3073         }
3074 
3075         final Source     source     = getCurrentSource();
3076         final Expression expression = throwNode.getExpression();
3077         final int        position   = throwNode.position();
3078         final int        line       = throwNode.getLineNumber();
3079         final int        column     = source.getColumn(position);
3080 
3081         // NOTE: we first evaluate the expression, and only after it was evaluated do we create the new ECMAException
3082         // object and then somewhat cumbersomely move it beneath the evaluated expression on the stack. The reason for
3083         // this is that if expression is optimistic (or contains an optimistic subexpression), we'd potentially access
3084         // the not-yet-<init>ialized object on the stack from the UnwarrantedOptimismException handler, and bytecode
3085         // verifier forbids that.
3086         loadExpressionAsObject(expression);
3087 
3088         method.load(source.getName());
3089         method.load(line);
3090         method.load(column);
3091         method.invoke(ECMAException.CREATE);
3092 
3093         method.beforeJoinPoint(throwNode);
3094         method.athrow();
3095 
3096         return false;
3097     }
3098 
3099     private Source getCurrentSource() {
3100         return lc.getCurrentFunction().getSource();
3101     }
3102 
3103     @Override
3104     public boolean enterTryNode(final TryNode tryNode) {
3105         if(!method.isReachable()) {
3106             return false;
3107         }
3108         enterStatement(tryNode);
3109 
3110         final Block       body        = tryNode.getBody();
3111         final List<Block> catchBlocks = tryNode.getCatchBlocks();
3112         final Symbol      vmException = tryNode.getException();
3113         final Label       entry       = new Label("try");
3114         final Label       recovery    = new Label("catch");
3115         final Label       exit        = new Label("end_try");
3116         final Label       skip        = new Label("skip");
3117 
3118         method.canThrow(recovery);
3119         // Effect any conversions that might be observed at the entry of the catch node before entering the try node.
3120         // This is because even the first instruction in the try block must be presumed to be able to transfer control
3121         // to the catch block. Note that this doesn't kill the original values; in this regard it works a lot like
3122         // conversions of assignments within the try block.
3123         method.beforeTry(tryNode, recovery);
3124         method.label(entry);
3125         catchLabels.push(recovery);
3126         try {
3127             body.accept(this);
3128         } finally {
3129             assert catchLabels.peek() == recovery;
3130             catchLabels.pop();
3131         }
3132 
3133         method.label(exit);
3134         final boolean bodyCanThrow = exit.isAfter(entry);
3135         if(!bodyCanThrow) {
3136             // The body can't throw an exception; don't even bother emitting the catch handlers, they're all dead code.
3137             return false;
3138         }
3139 
3140         method._try(entry, exit, recovery, Throwable.class);
3141 
3142         if (method.isReachable()) {
3143             method._goto(skip);
3144         }
3145         method._catch(recovery);
3146         method.store(vmException, EXCEPTION_TYPE);
3147 
3148         final int catchBlockCount = catchBlocks.size();
3149         final Label afterCatch = new Label("after_catch");
3150         for (int i = 0; i < catchBlockCount; i++) {
3151             assert method.isReachable();
3152             final Block catchBlock = catchBlocks.get(i);
3153 
3154             // Because of the peculiarities of the flow control, we need to use an explicit push/enterBlock/leaveBlock
3155             // here.
3156             lc.push(catchBlock);
3157             enterBlock(catchBlock);
3158 
3159             final CatchNode  catchNode          = (CatchNode)catchBlocks.get(i).getStatements().get(0);
3160             final IdentNode  exception          = catchNode.getException();
3161             final Expression exceptionCondition = catchNode.getExceptionCondition();
3162             final Block      catchBody          = catchNode.getBody();
3163 
3164             new Store<IdentNode>(exception) {
3165                 @Override
3166                 protected void storeNonDiscard() {
3167                     // This expression is neither part of a discard, nor needs to be left on the stack after it was
3168                     // stored, so we override storeNonDiscard to be a no-op.
3169                 }
3170 
3171                 @Override
3172                 protected void evaluate() {
3173                     if (catchNode.isSyntheticRethrow()) {
3174                         method.load(vmException, EXCEPTION_TYPE);
3175                         return;
3176                     }
3177                     /*
3178                      * If caught object is an instance of ECMAException, then
3179                      * bind obj.thrown to the script catch var. Or else bind the
3180                      * caught object itself to the script catch var.
3181                      */
3182                     final Label notEcmaException = new Label("no_ecma_exception");
3183                     method.load(vmException, EXCEPTION_TYPE).dup()._instanceof(ECMAException.class).ifeq(notEcmaException);
3184                     method.checkcast(ECMAException.class); //TODO is this necessary?
3185                     method.getField(ECMAException.THROWN);
3186                     method.label(notEcmaException);
3187                 }
3188             }.store();
3189 
3190             final boolean isConditionalCatch = exceptionCondition != null;
3191             final Label nextCatch;
3192             if (isConditionalCatch) {
3193                 loadExpressionAsBoolean(exceptionCondition);
3194                 nextCatch = new Label("next_catch");
3195                 method.ifeq(nextCatch);
3196             } else {
3197                 nextCatch = null;
3198             }
3199 
3200             catchBody.accept(this);
3201             leaveBlock(catchBlock);
3202             lc.pop(catchBlock);
3203             if(method.isReachable()) {
3204                 method._goto(afterCatch);
3205             }
3206             if(nextCatch != null) {
3207                 method.label(nextCatch);
3208             }
3209         }
3210 
3211         assert !method.isReachable();
3212         // afterCatch could be the same as skip, except that we need to establish that the vmException is dead.
3213         method.label(afterCatch);
3214         if(method.isReachable()) {
3215             method.markDeadLocalVariable(vmException);
3216         }
3217         method.label(skip);
3218 
3219         // Finally body is always inlined elsewhere so it doesn't need to be emitted
3220         return false;
3221     }
3222 
3223     @Override
3224     public boolean enterVarNode(final VarNode varNode) {
3225         if(!method.isReachable()) {
3226             return false;
3227         }
3228         final Expression init = varNode.getInit();
3229 
3230         if (init == null) {
3231             return false;
3232         }
3233 
3234         enterStatement(varNode);
3235 
3236         final IdentNode identNode = varNode.getName();
3237         final Symbol identSymbol = identNode.getSymbol();
3238         assert identSymbol != null : "variable node " + varNode + " requires a name with a symbol";
3239 
3240         assert method != null;
3241 
3242         final boolean needsScope = identSymbol.isScope();
3243         if (needsScope) {
3244             method.loadCompilerConstant(SCOPE);
3245         }
3246 
3247         if (needsScope) {
3248             loadExpressionUnbounded(init);
3249             final int flags = CALLSITE_SCOPE | getCallSiteFlags();
3250             if (isFastScope(identSymbol)) {
3251                 storeFastScopeVar(identSymbol, flags);
3252             } else {
3253                 method.dynamicSet(identNode.getName(), flags);
3254             }
3255         } else {
3256             final Type identType = identNode.getType();
3257             if(identType == Type.UNDEFINED) {
3258                 // The symbol must not be slotted; the initializer is either itself undefined (explicit assignment of
3259                 // undefined to undefined), or the left hand side is a dead variable.
3260                 assert !identNode.getSymbol().isScope();
3261                 assert init.getType() == Type.UNDEFINED || identNode.getSymbol().slotCount() == 0;
3262                 loadAndDiscard(init);
3263                 return false;
3264             }
3265             loadExpressionAsType(init, identType);
3266             storeIdentWithCatchConversion(identNode, identType);
3267         }
3268 
3269         return false;
3270     }
3271 
3272     private void storeIdentWithCatchConversion(final IdentNode identNode, final Type type) {
3273         // Assignments happening in try/catch blocks need to ensure that they also store a possibly wider typed value
3274         // that will be live at the exit from the try block
3275         final LocalVariableConversion conversion = identNode.getLocalVariableConversion();
3276         final Symbol symbol = identNode.getSymbol();
3277         if(conversion != null && conversion.isLive()) {
3278             assert symbol == conversion.getSymbol();
3279             assert symbol.isBytecodeLocal();
3280             // Only a single conversion from the target type to the join type is expected.
3281             assert conversion.getNext() == null;
3282             assert conversion.getFrom() == type;
3283             // We must propagate potential type change to the catch block
3284             final Label catchLabel = catchLabels.peek();
3285             assert catchLabel != METHOD_BOUNDARY; // ident conversion only exists in try blocks
3286             assert catchLabel.isReachable();
3287             final Type joinType = conversion.getTo();
3288             final Label.Stack catchStack = catchLabel.getStack();
3289             final int joinSlot = symbol.getSlot(joinType);
3290             // With nested try/catch blocks (incl. synthetic ones for finally), we can have a supposed conversion for
3291             // the exception symbol in the nested catch, but it isn't live in the outer catch block, so prevent doing
3292             // conversions for it. E.g. in "try { try { ... } catch(e) { e = 1; } } catch(e2) { ... }", we must not
3293             // introduce an I->O conversion on "e = 1" assignment as "e" is not live in "catch(e2)".
3294             if(catchStack.getUsedSlotsWithLiveTemporaries() > joinSlot) {
3295                 method.dup();
3296                 method.convert(joinType);
3297                 method.store(symbol, joinType);
3298                 catchLabel.getStack().onLocalStore(joinType, joinSlot, true);
3299                 method.canThrow(catchLabel);
3300                 // Store but keep the previous store live too.
3301                 method.store(symbol, type, false);
3302                 return;
3303             }
3304         }
3305 
3306         method.store(symbol, type, true);
3307     }
3308 
3309     @Override
3310     public boolean enterWhileNode(final WhileNode whileNode) {
3311         if(!method.isReachable()) {
3312             return false;
3313         }
3314         if(whileNode.isDoWhile()) {
3315             enterDoWhile(whileNode);
3316         } else {
3317             enterStatement(whileNode);
3318             enterForOrWhile(whileNode, null);
3319         }
3320         return false;
3321     }
3322 
3323     private void enterForOrWhile(final LoopNode loopNode, final JoinPredecessorExpression modify) {
3324         // NOTE: the usual pattern for compiling test-first loops is "GOTO test; body; test; IFNE body". We use the less
3325         // conventional "test; IFEQ break; body; GOTO test; break;". It has one extra unconditional GOTO in each repeat
3326         // of the loop, but it's not a problem for modern JIT compilers. We do this because our local variable type
3327         // tracking is unfortunately not really prepared for out-of-order execution, e.g. compiling the following
3328         // contrived but legal JavaScript code snippet would fail because the test changes the type of "i" from object
3329         // to double: var i = {valueOf: function() { return 1} }; while(--i >= 0) { ... }
3330         // Instead of adding more complexity to the local variable type tracking, we instead choose to emit this
3331         // different code shape.
3332         final int liveLocalsOnBreak = method.getUsedSlotsWithLiveTemporaries();
3333         final JoinPredecessorExpression test = loopNode.getTest();
3334         if(Expression.isAlwaysFalse(test)) {
3335             loadAndDiscard(test);
3336             return;
3337         }
3338 
3339         method.beforeJoinPoint(loopNode);
3340 
3341         final Label continueLabel = loopNode.getContinueLabel();
3342         final Label repeatLabel = modify != null ? new Label("for_repeat") : continueLabel;
3343         method.label(repeatLabel);
3344         final int liveLocalsOnContinue = method.getUsedSlotsWithLiveTemporaries();
3345 
3346         final Block   body                  = loopNode.getBody();
3347         final Label   breakLabel            = loopNode.getBreakLabel();
3348         final boolean testHasLiveConversion = test != null && LocalVariableConversion.hasLiveConversion(test);
3349 
3350         if(Expression.isAlwaysTrue(test)) {
3351             if(test != null) {
3352                 loadAndDiscard(test);
3353                 if(testHasLiveConversion) {
3354                     method.beforeJoinPoint(test);
3355                 }
3356             }
3357         } else if (test != null) {
3358             if (testHasLiveConversion) {
3359                 emitBranch(test.getExpression(), body.getEntryLabel(), true);
3360                 method.beforeJoinPoint(test);
3361                 method._goto(breakLabel);
3362             } else {
3363                 emitBranch(test.getExpression(), breakLabel, false);
3364             }
3365         }
3366 
3367         body.accept(this);
3368         if(repeatLabel != continueLabel) {
3369             emitContinueLabel(continueLabel, liveLocalsOnContinue);
3370         }
3371 
3372         if(method.isReachable()) {
3373             if(modify != null) {
3374                 lineNumber(loopNode);
3375                 loadAndDiscard(modify);
3376                 method.beforeJoinPoint(modify);
3377             }
3378             method._goto(repeatLabel);
3379         }
3380 
3381         method.breakLabel(breakLabel, liveLocalsOnBreak);
3382     }
3383 
3384     private void emitContinueLabel(final Label continueLabel, final int liveLocals) {
3385         final boolean reachable = method.isReachable();
3386         method.breakLabel(continueLabel, liveLocals);
3387         // If we reach here only through a continue statement (e.g. body does not exit normally) then the
3388         // continueLabel can have extra non-temp symbols (e.g. exception from a try/catch contained in the body). We
3389         // must make sure those are thrown away.
3390         if(!reachable) {
3391             method.undefineLocalVariables(lc.getUsedSlotCount(), false);
3392         }
3393     }
3394 
3395     private void enterDoWhile(final WhileNode whileNode) {
3396         final int liveLocalsOnContinueOrBreak = method.getUsedSlotsWithLiveTemporaries();
3397         method.beforeJoinPoint(whileNode);
3398 
3399         final Block body = whileNode.getBody();
3400         body.accept(this);
3401 
3402         emitContinueLabel(whileNode.getContinueLabel(), liveLocalsOnContinueOrBreak);
3403         if(method.isReachable()) {
3404             lineNumber(whileNode);
3405             final JoinPredecessorExpression test = whileNode.getTest();
3406             final Label bodyEntryLabel = body.getEntryLabel();
3407             final boolean testHasLiveConversion = LocalVariableConversion.hasLiveConversion(test);
3408             if(Expression.isAlwaysFalse(test)) {
3409                 loadAndDiscard(test);
3410                 if(testHasLiveConversion) {
3411                     method.beforeJoinPoint(test);
3412                 }
3413             } else if(testHasLiveConversion) {
3414                 // If we have conversions after the test in do-while, they need to be effected on both branches.
3415                 final Label beforeExit = new Label("do_while_preexit");
3416                 emitBranch(test.getExpression(), beforeExit, false);
3417                 method.beforeJoinPoint(test);
3418                 method._goto(bodyEntryLabel);
3419                 method.label(beforeExit);
3420                 method.beforeJoinPoint(test);
3421             } else {
3422                 emitBranch(test.getExpression(), bodyEntryLabel, true);
3423             }
3424         }
3425         method.breakLabel(whileNode.getBreakLabel(), liveLocalsOnContinueOrBreak);
3426     }
3427 
3428 
3429     @Override
3430     public boolean enterWithNode(final WithNode withNode) {
3431         if(!method.isReachable()) {
3432             return false;
3433         }
3434         enterStatement(withNode);
3435         final Expression expression = withNode.getExpression();
3436         final Block      body       = withNode.getBody();
3437 
3438         // It is possible to have a "pathological" case where the with block does not reference *any* identifiers. It's
3439         // pointless, but legal. In that case, if nothing else in the method forced the assignment of a slot to the
3440         // scope object, its' possible that it won't have a slot assigned. In this case we'll only evaluate expression
3441         // for its side effect and visit the body, and not bother opening and closing a WithObject.
3442         final boolean hasScope = method.hasScope();
3443 
3444         if (hasScope) {
3445             method.loadCompilerConstant(SCOPE);
3446         }
3447 
3448         loadExpressionAsObject(expression);
3449 
3450         final Label tryLabel;
3451         if (hasScope) {
3452             // Construct a WithObject if we have a scope
3453             method.invoke(ScriptRuntime.OPEN_WITH);
3454             method.storeCompilerConstant(SCOPE);
3455             tryLabel = new Label("with_try");
3456             method.label(tryLabel);
3457         } else {
3458             // We just loaded the expression for its side effect and to check
3459             // for null or undefined value.
3460             globalCheckObjectCoercible();
3461             tryLabel = null;
3462         }
3463 
3464         // Always process body
3465         body.accept(this);
3466 
3467         if (hasScope) {
3468             // Ensure we always close the WithObject
3469             final Label endLabel   = new Label("with_end");
3470             final Label catchLabel = new Label("with_catch");
3471             final Label exitLabel  = new Label("with_exit");
3472 
3473             method.label(endLabel);
3474             // Somewhat conservatively presume that if the body is not empty, it can throw an exception. In any case,
3475             // we must prevent trying to emit a try-catch for empty range, as it causes a verification error.
3476             final boolean bodyCanThrow = endLabel.isAfter(tryLabel);
3477             if(bodyCanThrow) {
3478                 method._try(tryLabel, endLabel, catchLabel);
3479             }
3480 
3481             final boolean reachable = method.isReachable();
3482             if(reachable) {
3483                 popScope();
3484                 if(bodyCanThrow) {
3485                     method._goto(exitLabel);
3486                 }
3487             }
3488 
3489             if(bodyCanThrow) {
3490                 method._catch(catchLabel);
3491                 popScopeException();
3492                 method.athrow();
3493                 if(reachable) {
3494                     method.label(exitLabel);
3495                 }
3496             }
3497         }
3498         return false;
3499     }
3500 
3501     private void loadADD(final UnaryNode unaryNode, final TypeBounds resultBounds) {
3502         loadExpression(unaryNode.getExpression(), resultBounds.booleanToInt().notWiderThan(Type.NUMBER));
3503         if(method.peekType() == Type.BOOLEAN) {
3504             // It's a no-op in bytecode, but we must make sure it is treated as an int for purposes of type signatures
3505             method.convert(Type.INT);
3506         }
3507     }
3508 
3509     private void loadBIT_NOT(final UnaryNode unaryNode) {
3510         loadExpression(unaryNode.getExpression(), TypeBounds.INT).load(-1).xor();
3511     }
3512 
3513     private void loadDECINC(final UnaryNode unaryNode) {
3514         final Expression operand     = unaryNode.getExpression();
3515         final Type       type        = unaryNode.getType();
3516         final TypeBounds typeBounds  = new TypeBounds(type, Type.NUMBER);
3517         final TokenType  tokenType   = unaryNode.tokenType();
3518         final boolean    isPostfix   = tokenType == TokenType.DECPOSTFIX || tokenType == TokenType.INCPOSTFIX;
3519         final boolean    isIncrement = tokenType == TokenType.INCPREFIX || tokenType == TokenType.INCPOSTFIX;
3520 
3521         assert !type.isObject();
3522 
3523         new SelfModifyingStore<UnaryNode>(unaryNode, operand) {
3524 
3525             private void loadRhs() {
3526                 loadExpression(operand, typeBounds, true);
3527             }
3528 
3529             @Override
3530             protected void evaluate() {
3531                 if(isPostfix) {
3532                     loadRhs();
3533                 } else {
3534                     new OptimisticOperation(unaryNode, typeBounds) {
3535                         @Override
3536                         void loadStack() {
3537                             loadRhs();
3538                             loadMinusOne();
3539                         }
3540                         @Override
3541                         void consumeStack() {
3542                             doDecInc(getProgramPoint());
3543                         }
3544                     }.emit(getOptimisticIgnoreCountForSelfModifyingExpression(operand));
3545                 }
3546             }
3547 
3548             @Override
3549             protected void storeNonDiscard() {
3550                 super.storeNonDiscard();
3551                 if (isPostfix) {
3552                     new OptimisticOperation(unaryNode, typeBounds) {
3553                         @Override
3554                         void loadStack() {
3555                             loadMinusOne();
3556                         }
3557                         @Override
3558                         void consumeStack() {
3559                             doDecInc(getProgramPoint());
3560                         }
3561                     }.emit(1); // 1 for non-incremented result on the top of the stack pushed in evaluate()
3562                 }
3563             }
3564 
3565             private void loadMinusOne() {
3566                 if (type.isInteger()) {
3567                     method.load(isIncrement ? 1 : -1);
3568                 } else if (type.isLong()) {
3569                     method.load(isIncrement ? 1L : -1L);
3570                 } else {
3571                     method.load(isIncrement ? 1.0 : -1.0);
3572                 }
3573             }
3574 
3575             private void doDecInc(final int programPoint) {
3576                 method.add(programPoint);
3577             }
3578         }.store();
3579     }
3580 
3581     private static int getOptimisticIgnoreCountForSelfModifyingExpression(final Expression target) {
3582         return target instanceof AccessNode ? 1 : target instanceof IndexNode ? 2 : 0;
3583     }
3584 
3585     private void loadAndDiscard(final Expression expr) {
3586         // TODO: move checks for discarding to actual expression load code (e.g. as we do with void). That way we might
3587         // be able to eliminate even more checks.
3588         if(expr instanceof PrimitiveLiteralNode | isLocalVariable(expr)) {
3589             assert lc.getCurrentDiscard() != expr;
3590             // Don't bother evaluating expressions without side effects. Typical usage is "void 0" for reliably generating
3591             // undefined.
3592             return;
3593         }
3594 
3595         lc.pushDiscard(expr);
3596         loadExpression(expr, TypeBounds.UNBOUNDED);
3597         if (lc.getCurrentDiscard() == expr) {
3598             assert !expr.isAssignment();
3599             // NOTE: if we had a way to load with type void, we could avoid popping
3600             method.pop();
3601             lc.popDiscard();
3602         }
3603     }
3604 
3605     private void loadNEW(final UnaryNode unaryNode) {
3606         final CallNode callNode = (CallNode)unaryNode.getExpression();
3607         final List<Expression> args   = callNode.getArgs();
3608 
3609         // Load function reference.
3610         loadExpressionAsObject(callNode.getFunction()); // must detect type error
3611 
3612         method.dynamicNew(1 + loadArgs(args), getCallSiteFlags());
3613     }
3614 
3615     private void loadNOT(final UnaryNode unaryNode) {
3616         final Expression expr = unaryNode.getExpression();
3617         if(expr instanceof UnaryNode && expr.isTokenType(TokenType.NOT)) {
3618             // !!x is idiomatic boolean cast in JavaScript
3619             loadExpressionAsBoolean(((UnaryNode)expr).getExpression());
3620         } else {
3621             final Label trueLabel  = new Label("true");
3622             final Label afterLabel = new Label("after");
3623 
3624             emitBranch(expr, trueLabel, true);
3625             method.load(true);
3626             method._goto(afterLabel);
3627             method.label(trueLabel);
3628             method.load(false);
3629             method.label(afterLabel);
3630         }
3631     }
3632 
3633     private void loadSUB(final UnaryNode unaryNode, final TypeBounds resultBounds) {
3634         final Type type = unaryNode.getType();
3635         assert type.isNumeric();
3636         final TypeBounds numericBounds = resultBounds.booleanToInt();
3637         new OptimisticOperation(unaryNode, numericBounds) {
3638             @Override
3639             void loadStack() {
3640                 final Expression expr = unaryNode.getExpression();
3641                 loadExpression(expr, numericBounds.notWiderThan(Type.NUMBER));
3642             }
3643             @Override
3644             void consumeStack() {
3645                 // Must do an explicit conversion to the operation's type when it's double so that we correctly handle
3646                 // negation of an int 0 to a double -0. With this, we get the correct negation of a local variable after
3647                 // it deoptimized, e.g. "iload_2; i2d; dneg". Without this, we get "iload_2; ineg; i2d".
3648                 if(type.isNumber()) {
3649                     method.convert(type);
3650                 }
3651                 method.neg(getProgramPoint());
3652             }
3653         }.emit();
3654     }
3655 
3656     public void loadVOID(final UnaryNode unaryNode, final TypeBounds resultBounds) {
3657         loadAndDiscard(unaryNode.getExpression());
3658         if(lc.getCurrentDiscard() == unaryNode) {
3659             lc.popDiscard();
3660         } else {
3661             method.loadUndefined(resultBounds.widest);
3662         }
3663     }
3664 
3665     public void loadADD(final BinaryNode binaryNode, final TypeBounds resultBounds) {
3666         new OptimisticOperation(binaryNode, resultBounds) {
3667             @Override
3668             void loadStack() {
3669                 final TypeBounds operandBounds;
3670                 final boolean isOptimistic = isValid(getProgramPoint());
3671                 if(isOptimistic) {
3672                     operandBounds = new TypeBounds(binaryNode.getType(), Type.OBJECT);
3673                 } else {
3674                     // Non-optimistic, non-FP +. Allow it to overflow.
3675                     operandBounds = new TypeBounds(binaryNode.getWidestOperandType(), Type.OBJECT);
3676                 }
3677                 loadBinaryOperands(binaryNode.lhs(), binaryNode.rhs(), operandBounds, false);
3678             }
3679 
3680             @Override
3681             void consumeStack() {
3682                 method.add(getProgramPoint());
3683             }
3684         }.emit();
3685     }
3686 
3687     private void loadAND_OR(final BinaryNode binaryNode, final TypeBounds resultBounds, final boolean isAnd) {
3688         final Type narrowestOperandType = Type.widestReturnType(binaryNode.lhs().getType(), binaryNode.rhs().getType());
3689 
3690         final Label skip = new Label("skip");
3691         if(narrowestOperandType == Type.BOOLEAN) {
3692             // optimize all-boolean logical expressions
3693             final Label onTrue = new Label("andor_true");
3694             emitBranch(binaryNode, onTrue, true);
3695             method.load(false);
3696             method._goto(skip);
3697             method.label(onTrue);
3698             method.load(true);
3699             method.label(skip);
3700             return;
3701         }
3702 
3703         final TypeBounds outBounds = resultBounds.notNarrowerThan(narrowestOperandType);
3704         final JoinPredecessorExpression lhs = (JoinPredecessorExpression)binaryNode.lhs();
3705         final boolean lhsConvert = LocalVariableConversion.hasLiveConversion(lhs);
3706         final Label evalRhs = lhsConvert ? new Label("eval_rhs") : null;
3707 
3708         loadExpression(lhs, outBounds).dup().convert(Type.BOOLEAN);
3709         if (isAnd) {
3710             if(lhsConvert) {
3711                 method.ifne(evalRhs);
3712             } else {
3713                 method.ifeq(skip);
3714             }
3715         } else if(lhsConvert) {
3716             method.ifeq(evalRhs);
3717         } else {
3718             method.ifne(skip);
3719         }
3720 
3721         if(lhsConvert) {
3722             method.beforeJoinPoint(lhs);
3723             method._goto(skip);
3724             method.label(evalRhs);
3725         }
3726 
3727         method.pop();
3728         final JoinPredecessorExpression rhs = (JoinPredecessorExpression)binaryNode.rhs();
3729         loadExpression(rhs, outBounds);
3730         method.beforeJoinPoint(rhs);
3731         method.label(skip);
3732     }
3733 
3734     private static boolean isLocalVariable(final Expression lhs) {
3735         return lhs instanceof IdentNode && isLocalVariable((IdentNode)lhs);
3736     }
3737 
3738     private static boolean isLocalVariable(final IdentNode lhs) {
3739         return lhs.getSymbol().isBytecodeLocal();
3740     }
3741 
3742     // NOTE: does not use resultBounds as the assignment is driven by the type of the RHS
3743     private void loadASSIGN(final BinaryNode binaryNode) {
3744         final Expression lhs = binaryNode.lhs();
3745         final Expression rhs = binaryNode.rhs();
3746 
3747         final Type rhsType = rhs.getType();
3748         // Detect dead assignments
3749         if(lhs instanceof IdentNode) {
3750             final Symbol symbol = ((IdentNode)lhs).getSymbol();
3751             if(!symbol.isScope() && !symbol.hasSlotFor(rhsType) && lc.getCurrentDiscard() == binaryNode) {
3752                 loadAndDiscard(rhs);
3753                 lc.popDiscard();
3754                 method.markDeadLocalVariable(symbol);
3755                 return;
3756             }
3757         }
3758 
3759         new Store<BinaryNode>(binaryNode, lhs) {
3760             @Override
3761             protected void evaluate() {
3762                 // NOTE: we're loading with "at least as wide as" so optimistic operations on the right hand side
3763                 // remain optimistic, and then explicitly convert to the required type if needed.
3764                 loadExpressionAsType(rhs, rhsType);
3765             }
3766         }.store();
3767     }
3768 
3769     /**
3770      * Binary self-assignment that can be optimistic: +=, -=, *=, and /=.
3771      */
3772     private abstract class BinaryOptimisticSelfAssignment extends SelfModifyingStore<BinaryNode> {
3773 
3774         /**
3775          * Constructor
3776          *
3777          * @param node the assign op node
3778          */
3779         BinaryOptimisticSelfAssignment(final BinaryNode node) {
3780             super(node, node.lhs());
3781         }
3782 
3783         protected abstract void op(OptimisticOperation oo);
3784 
3785         @Override
3786         protected void evaluate() {
3787             final Expression lhs = assignNode.lhs();
3788             final Type widest = assignNode.isTokenType(TokenType.ASSIGN_ADD) ? Type.OBJECT : assignNode.getWidestOperationType();
3789             final TypeBounds bounds = new TypeBounds(assignNode.getType(), widest);
3790             new OptimisticOperation(assignNode, bounds) {
3791                 @Override
3792                 void loadStack() {
3793                     loadBinaryOperands(lhs, assignNode.rhs(), bounds, true);
3794                 }
3795                 @Override
3796                 void consumeStack() {
3797                     op(this);
3798                 }
3799             }.emit(getOptimisticIgnoreCountForSelfModifyingExpression(lhs));
3800             method.convert(assignNode.getType());
3801         }
3802     }
3803 
3804     /**
3805      * Non-optimistic binary self-assignment operation. Basically, everything except +=, -=, *=, and /=.
3806      */
3807     private abstract class BinarySelfAssignment extends SelfModifyingStore<BinaryNode> {
3808         BinarySelfAssignment(final BinaryNode node) {
3809             super(node, node.lhs());
3810         }
3811 
3812         protected abstract void op();
3813 
3814         @Override
3815         protected void evaluate() {
3816             loadBinaryOperands(assignNode.lhs(), assignNode.rhs(), TypeBounds.UNBOUNDED.notWiderThan(assignNode.getWidestOperandType()), true);
3817             op();
3818         }
3819     }
3820 
3821     private void loadASSIGN_ADD(final BinaryNode binaryNode) {
3822         new BinaryOptimisticSelfAssignment(binaryNode) {
3823             @Override
3824             protected void op(final OptimisticOperation oo) {
3825                 assert !(binaryNode.getType().isObject() && oo.isOptimistic);
3826                 method.add(oo.getProgramPoint());
3827             }
3828         }.store();
3829     }
3830 
3831     private void loadASSIGN_BIT_AND(final BinaryNode binaryNode) {
3832         new BinarySelfAssignment(binaryNode) {
3833             @Override
3834             protected void op() {
3835                 method.and();
3836             }
3837         }.store();
3838     }
3839 
3840     private void loadASSIGN_BIT_OR(final BinaryNode binaryNode) {
3841         new BinarySelfAssignment(binaryNode) {
3842             @Override
3843             protected void op() {
3844                 method.or();
3845             }
3846         }.store();
3847     }
3848 
3849     private void loadASSIGN_BIT_XOR(final BinaryNode binaryNode) {
3850         new BinarySelfAssignment(binaryNode) {
3851             @Override
3852             protected void op() {
3853                 method.xor();
3854             }
3855         }.store();
3856     }
3857 
3858     private void loadASSIGN_DIV(final BinaryNode binaryNode) {
3859         new BinaryOptimisticSelfAssignment(binaryNode) {
3860             @Override
3861             protected void op(final OptimisticOperation oo) {
3862                 method.div(oo.getProgramPoint());
3863             }
3864         }.store();
3865     }
3866 
3867     private void loadASSIGN_MOD(final BinaryNode binaryNode) {
3868         new BinaryOptimisticSelfAssignment(binaryNode) {
3869             @Override
3870             protected void op(final OptimisticOperation oo) {
3871                 method.rem(oo.getProgramPoint());
3872             }
3873         }.store();
3874     }
3875 
3876     private void loadASSIGN_MUL(final BinaryNode binaryNode) {
3877         new BinaryOptimisticSelfAssignment(binaryNode) {
3878             @Override
3879             protected void op(final OptimisticOperation oo) {
3880                 method.mul(oo.getProgramPoint());
3881             }
3882         }.store();
3883     }
3884 
3885     private void loadASSIGN_SAR(final BinaryNode binaryNode) {
3886         new BinarySelfAssignment(binaryNode) {
3887             @Override
3888             protected void op() {
3889                 method.sar();
3890             }
3891         }.store();
3892     }
3893 
3894     private void loadASSIGN_SHL(final BinaryNode binaryNode) {
3895         new BinarySelfAssignment(binaryNode) {
3896             @Override
3897             protected void op() {
3898                 method.shl();
3899             }
3900         }.store();
3901     }
3902 
3903     private void loadASSIGN_SHR(final BinaryNode binaryNode) {
3904         new BinarySelfAssignment(binaryNode) {
3905             @Override
3906             protected void op() {
3907                 doSHR();
3908             }
3909 
3910         }.store();
3911     }
3912 
3913     private void doSHR() {
3914         // TODO: make SHR optimistic
3915         method.shr().convert(Type.LONG).load(JSType.MAX_UINT).and();
3916     }
3917 
3918     private void loadASSIGN_SUB(final BinaryNode binaryNode) {
3919         new BinaryOptimisticSelfAssignment(binaryNode) {
3920             @Override
3921             protected void op(final OptimisticOperation oo) {
3922                 method.sub(oo.getProgramPoint());
3923             }
3924         }.store();
3925     }
3926 
3927     /**
3928      * Helper class for binary arithmetic ops
3929      */
3930     private abstract class BinaryArith {
3931         protected abstract void op(int programPoint);
3932 
3933         protected void evaluate(final BinaryNode node, final TypeBounds resultBounds) {
3934             final TypeBounds numericBounds = resultBounds.booleanToInt().objectToNumber();
3935             new OptimisticOperation(node, numericBounds) {
3936                 @Override
3937                 void loadStack() {
3938                     final TypeBounds operandBounds;
3939                     if(numericBounds.narrowest == Type.NUMBER) {
3940                         // Result should be double always. Propagate it into the operands so we don't have lots of I2D
3941                         // and L2D after operand evaluation.
3942                         assert numericBounds.widest == Type.NUMBER;
3943                         operandBounds = numericBounds;
3944                     } else {
3945                         final boolean isOptimistic = isValid(getProgramPoint());
3946                         if(isOptimistic) {
3947                             operandBounds = new TypeBounds(node.getType(), Type.NUMBER);
3948                         } else if(node.isTokenType(TokenType.DIV) || node.isTokenType(TokenType.MOD)) {
3949                             // Non-optimistic division must always take double arguments as its result must also be
3950                             // double.
3951                             operandBounds = TypeBounds.NUMBER;
3952                         } else {
3953                             // Non-optimistic, non-FP subtraction or multiplication. Allow them to overflow.
3954                             operandBounds = new TypeBounds(Type.narrowest(node.getWidestOperandType(),
3955                                     numericBounds.widest), Type.NUMBER);
3956                         }
3957                     }
3958                     loadBinaryOperands(node.lhs(), node.rhs(), operandBounds, false);
3959                 }
3960 
3961                 @Override
3962                 void consumeStack() {
3963                     op(getProgramPoint());
3964                 }
3965             }.emit();
3966         }
3967     }
3968 
3969     private void loadBIT_AND(final BinaryNode binaryNode) {
3970         loadBinaryOperands(binaryNode);
3971         method.and();
3972     }
3973 
3974     private void loadBIT_OR(final BinaryNode binaryNode) {
3975         loadBinaryOperands(binaryNode);
3976         method.or();
3977     }
3978 
3979     private void loadBIT_XOR(final BinaryNode binaryNode) {
3980         loadBinaryOperands(binaryNode);
3981         method.xor();
3982     }
3983 
3984     private void loadCOMMARIGHT(final BinaryNode binaryNode, final TypeBounds resultBounds) {
3985         loadAndDiscard(binaryNode.lhs());
3986         loadExpression(binaryNode.rhs(), resultBounds);
3987     }
3988 
3989     private void loadCOMMALEFT(final BinaryNode binaryNode, final TypeBounds resultBounds) {
3990         loadExpression(binaryNode.lhs(), resultBounds);
3991         loadAndDiscard(binaryNode.rhs());
3992     }
3993 
3994     private void loadDIV(final BinaryNode binaryNode, final TypeBounds resultBounds) {
3995         new BinaryArith() {
3996             @Override
3997             protected void op(final int programPoint) {
3998                 method.div(programPoint);
3999             }
4000         }.evaluate(binaryNode, resultBounds);
4001     }
4002 
4003     private void loadCmp(final BinaryNode binaryNode, final Condition cond) {
4004         assert comparisonOperandsArePrimitive(binaryNode) : binaryNode;
4005         loadBinaryOperands(binaryNode);
4006 
4007         final Label trueLabel  = new Label("trueLabel");
4008         final Label afterLabel = new Label("skip");
4009 
4010         method.conditionalJump(cond, trueLabel);
4011 
4012         method.load(Boolean.FALSE);
4013         method._goto(afterLabel);
4014         method.label(trueLabel);
4015         method.load(Boolean.TRUE);
4016         method.label(afterLabel);
4017     }
4018 
4019     private static boolean comparisonOperandsArePrimitive(final BinaryNode binaryNode) {
4020         final Type widest = Type.widest(binaryNode.lhs().getType(), binaryNode.rhs().getType());
4021         return widest.isNumeric() || widest.isBoolean();
4022     }
4023 
4024     private void loadMOD(final BinaryNode binaryNode, final TypeBounds resultBounds) {
4025         new BinaryArith() {
4026             @Override
4027             protected void op(final int programPoint) {
4028                 method.rem(programPoint);
4029             }
4030         }.evaluate(binaryNode, resultBounds);
4031     }
4032 
4033     private void loadMUL(final BinaryNode binaryNode, final TypeBounds resultBounds) {
4034         new BinaryArith() {
4035             @Override
4036             protected void op(final int programPoint) {
4037                 method.mul(programPoint);
4038             }
4039         }.evaluate(binaryNode, resultBounds);
4040     }
4041 
4042     private void loadSAR(final BinaryNode binaryNode) {
4043         loadBinaryOperands(binaryNode);
4044         method.sar();
4045     }
4046 
4047     private void loadSHL(final BinaryNode binaryNode) {
4048         loadBinaryOperands(binaryNode);
4049         method.shl();
4050     }
4051 
4052     private void loadSHR(final BinaryNode binaryNode) {
4053         loadBinaryOperands(binaryNode);
4054         doSHR();
4055     }
4056 
4057     private void loadSUB(final BinaryNode binaryNode, final TypeBounds resultBounds) {
4058         new BinaryArith() {
4059             @Override
4060             protected void op(final int programPoint) {
4061                 method.sub(programPoint);
4062             }
4063         }.evaluate(binaryNode, resultBounds);
4064     }
4065 
4066     @Override
4067     public boolean enterLabelNode(final LabelNode labelNode) {
4068         labeledBlockBreakLiveLocals.push(lc.getUsedSlotCount());
4069         return true;
4070     }
4071 
4072     @Override
4073     protected boolean enterDefault(final Node node) {
4074         throw new AssertionError("Code generator entered node of type " + node.getClass().getName());
4075     }
4076 
4077     private void loadTernaryNode(final TernaryNode ternaryNode, final TypeBounds resultBounds) {
4078         final Expression test = ternaryNode.getTest();
4079         final JoinPredecessorExpression trueExpr  = ternaryNode.getTrueExpression();
4080         final JoinPredecessorExpression falseExpr = ternaryNode.getFalseExpression();
4081 
4082         final Label falseLabel = new Label("ternary_false");
4083         final Label exitLabel  = new Label("ternary_exit");
4084 
4085         final Type outNarrowest = Type.narrowest(resultBounds.widest, Type.generic(Type.widestReturnType(trueExpr.getType(), falseExpr.getType())));
4086         final TypeBounds outBounds = resultBounds.notNarrowerThan(outNarrowest);
4087 
4088         emitBranch(test, falseLabel, false);
4089 
4090         loadExpression(trueExpr.getExpression(), outBounds);
4091         assert Type.generic(method.peekType()) == outBounds.narrowest;
4092         method.beforeJoinPoint(trueExpr);
4093         method._goto(exitLabel);
4094         method.label(falseLabel);
4095         loadExpression(falseExpr.getExpression(), outBounds);
4096         assert Type.generic(method.peekType()) == outBounds.narrowest;
4097         method.beforeJoinPoint(falseExpr);
4098         method.label(exitLabel);
4099     }
4100 
4101     /**
4102      * Generate all shared scope calls generated during codegen.
4103      */
4104     void generateScopeCalls() {
4105         for (final SharedScopeCall scopeAccess : lc.getScopeCalls()) {
4106             scopeAccess.generateScopeCall();
4107         }
4108     }
4109 
4110     /**
4111      * Debug code used to print symbols
4112      *
4113      * @param block the block we are in
4114      * @param ident identifier for block or function where applicable
4115      */
4116     private void printSymbols(final Block block, final String ident) {
4117         if (!compiler.getScriptEnvironment()._print_symbols) {
4118             return;
4119         }
4120 
4121         final PrintWriter out = compiler.getScriptEnvironment().getErr();
4122         out.println("[BLOCK in '" + ident + "']");
4123         if (!block.printSymbols(out)) {
4124             out.println("<no symbols>");
4125         }
4126         out.println();
4127     }
4128 
4129 
4130     /**
4131      * The difference between a store and a self modifying store is that
4132      * the latter may load part of the target on the stack, e.g. the base
4133      * of an AccessNode or the base and index of an IndexNode. These are used
4134      * both as target and as an extra source. Previously it was problematic
4135      * for self modifying stores if the target/lhs didn't belong to one
4136      * of three trivial categories: IdentNode, AcessNodes, IndexNodes. In that
4137      * case it was evaluated and tagged as "resolved", which meant at the second
4138      * time the lhs of this store was read (e.g. in a = a (second) + b for a += b,
4139      * it would be evaluated to a nop in the scope and cause stack underflow
4140      *
4141      * see NASHORN-703
4142      *
4143      * @param <T>
4144      */
4145     private abstract class SelfModifyingStore<T extends Expression> extends Store<T> {
4146         protected SelfModifyingStore(final T assignNode, final Expression target) {
4147             super(assignNode, target);
4148         }
4149 
4150         @Override
4151         protected boolean isSelfModifying() {
4152             return true;
4153         }
4154     }
4155 
4156     /**
4157      * Helper class to generate stores
4158      */
4159     private abstract class Store<T extends Expression> {
4160 
4161         /** An assignment node, e.g. x += y */
4162         protected final T assignNode;
4163 
4164         /** The target node to store to, e.g. x */
4165         private final Expression target;
4166 
4167         /** How deep on the stack do the arguments go if this generates an indy call */
4168         private int depth;
4169 
4170         /** If we have too many arguments, we need temporary storage, this is stored in 'quick' */
4171         private IdentNode quick;
4172 
4173         /**
4174          * Constructor
4175          *
4176          * @param assignNode the node representing the whole assignment
4177          * @param target     the target node of the assignment (destination)
4178          */
4179         protected Store(final T assignNode, final Expression target) {
4180             this.assignNode = assignNode;
4181             this.target = target;
4182         }
4183 
4184         /**
4185          * Constructor
4186          *
4187          * @param assignNode the node representing the whole assignment
4188          */
4189         protected Store(final T assignNode) {
4190             this(assignNode, assignNode);
4191         }
4192 
4193         /**
4194          * Is this a self modifying store operation, e.g. *= or ++
4195          * @return true if self modifying store
4196          */
4197         protected boolean isSelfModifying() {
4198             return false;
4199         }
4200 
4201         private void prologue() {
4202             /**
4203              * This loads the parts of the target, e.g base and index. they are kept
4204              * on the stack throughout the store and used at the end to execute it
4205              */
4206 
4207             target.accept(new NodeVisitor<LexicalContext>(new LexicalContext()) {
4208                 @Override
4209                 public boolean enterIdentNode(final IdentNode node) {
4210                     if (node.getSymbol().isScope()) {
4211                         method.loadCompilerConstant(SCOPE);
4212                         depth += Type.SCOPE.getSlots();
4213                         assert depth == 1;
4214                     }
4215                     return false;
4216                 }
4217 
4218                 private void enterBaseNode() {
4219                     assert target instanceof BaseNode : "error - base node " + target + " must be instanceof BaseNode";
4220                     final BaseNode   baseNode = (BaseNode)target;
4221                     final Expression base     = baseNode.getBase();
4222 
4223                     loadExpressionAsObject(base);
4224                     depth += Type.OBJECT.getSlots();
4225                     assert depth == 1;
4226 
4227                     if (isSelfModifying()) {
4228                         method.dup();
4229                     }
4230                 }
4231 
4232                 @Override
4233                 public boolean enterAccessNode(final AccessNode node) {
4234                     enterBaseNode();
4235                     return false;
4236                 }
4237 
4238                 @Override
4239                 public boolean enterIndexNode(final IndexNode node) {
4240                     enterBaseNode();
4241 
4242                     final Expression index = node.getIndex();
4243                     if (!index.getType().isNumeric()) {
4244                         // could be boolean here as well
4245                         loadExpressionAsObject(index);
4246                     } else {
4247                         loadExpressionUnbounded(index);
4248                     }
4249                     depth += index.getType().getSlots();
4250 
4251                     if (isSelfModifying()) {
4252                         //convert "base base index" to "base index base index"
4253                         method.dup(1);
4254                     }
4255 
4256                     return false;
4257                 }
4258 
4259             });
4260         }
4261 
4262         /**
4263          * Generates an extra local variable, always using the same slot, one that is available after the end of the
4264          * frame.
4265          *
4266          * @param type the type of the variable
4267          *
4268          * @return the quick variable
4269          */
4270         private IdentNode quickLocalVariable(final Type type) {
4271             final String name = lc.getCurrentFunction().uniqueName(QUICK_PREFIX.symbolName());
4272             final Symbol symbol = new Symbol(name, IS_INTERNAL | HAS_SLOT);
4273             symbol.setHasSlotFor(type);
4274             symbol.setFirstSlot(lc.quickSlot(type));
4275 
4276             final IdentNode quickIdent = IdentNode.createInternalIdentifier(symbol).setType(type);
4277 
4278             return quickIdent;
4279         }
4280 
4281         // store the result that "lives on" after the op, e.g. "i" in i++ postfix.
4282         protected void storeNonDiscard() {
4283             if (lc.getCurrentDiscard() == assignNode) {
4284                 assert assignNode.isAssignment();
4285                 lc.popDiscard();
4286                 return;
4287             }
4288 
4289             if (method.dup(depth) == null) {
4290                 method.dup();
4291                 final Type quickType = method.peekType();
4292                 this.quick = quickLocalVariable(quickType);
4293                 final Symbol quickSymbol = quick.getSymbol();
4294                 method.storeTemp(quickType, quickSymbol.getFirstSlot());
4295             }
4296         }
4297 
4298         private void epilogue() {
4299             /**
4300              * Take the original target args from the stack and use them
4301              * together with the value to be stored to emit the store code
4302              *
4303              * The case that targetSymbol is in scope (!hasSlot) and we actually
4304              * need to do a conversion on non-equivalent types exists, but is
4305              * very rare. See for example test/script/basic/access-specializer.js
4306              */
4307             target.accept(new NodeVisitor<LexicalContext>(new LexicalContext()) {
4308                 @Override
4309                 protected boolean enterDefault(final Node node) {
4310                     throw new AssertionError("Unexpected node " + node + " in store epilogue");
4311                 }
4312 
4313                 @Override
4314                 public boolean enterIdentNode(final IdentNode node) {
4315                     final Symbol symbol = node.getSymbol();
4316                     assert symbol != null;
4317                     if (symbol.isScope()) {
4318                         final int flags = CALLSITE_SCOPE | getCallSiteFlags();
4319                         if (isFastScope(symbol)) {
4320                             storeFastScopeVar(symbol, flags);
4321                         } else {
4322                             method.dynamicSet(node.getName(), flags);
4323                         }
4324                     } else {
4325                         final Type storeType = assignNode.getType();
4326                         method.convert(storeType);
4327                         storeIdentWithCatchConversion(node, storeType);
4328                     }
4329                     return false;
4330 
4331                 }
4332 
4333                 @Override
4334                 public boolean enterAccessNode(final AccessNode node) {
4335                     method.dynamicSet(node.getProperty(), getCallSiteFlags());
4336                     return false;
4337                 }
4338 
4339                 @Override
4340                 public boolean enterIndexNode(final IndexNode node) {
4341                     method.dynamicSetIndex(getCallSiteFlags());
4342                     return false;
4343                 }
4344             });
4345 
4346 
4347             // whatever is on the stack now is the final answer
4348         }
4349 
4350         protected abstract void evaluate();
4351 
4352         void store() {
4353             prologue();
4354             evaluate(); // leaves an operation of whatever the operationType was on the stack
4355             storeNonDiscard();
4356             epilogue();
4357             if (quick != null) {
4358                 method.load(quick);
4359             }
4360         }
4361     }
4362 
4363     private void newFunctionObject(final FunctionNode functionNode, final boolean addInitializer) {
4364         assert lc.peek() == functionNode;
4365 
4366         final int fnId = functionNode.getId();
4367 
4368         final RecompilableScriptFunctionData data = compiler.getScriptFunctionData(fnId);
4369 
4370         assert data != null : functionNode.getName() + " has no data";
4371 
4372         if (functionNode.isProgram() && !compiler.isOnDemandCompilation()) {
4373             final CompileUnit fnUnit = functionNode.getCompileUnit();
4374             final MethodEmitter createFunction = fnUnit.getClassEmitter().method(
4375                     EnumSet.of(Flag.PUBLIC, Flag.STATIC), CREATE_PROGRAM_FUNCTION.symbolName(),
4376                     ScriptFunction.class, ScriptObject.class);
4377             createFunction.begin();
4378             createFunction._new(SCRIPTFUNCTION_IMPL_NAME, SCRIPTFUNCTION_IMPL_TYPE).dup();
4379             loadConstant(data, fnUnit, createFunction);
4380             createFunction.load(SCOPE_TYPE, 0);
4381             createFunction.invoke(constructorNoLookup(SCRIPTFUNCTION_IMPL_NAME, RecompilableScriptFunctionData.class, ScriptObject.class));
4382             createFunction._return();
4383             createFunction.end();
4384         }
4385 
4386         if (addInitializer && !initializedFunctionIds.contains(fnId) && !compiler.isOnDemandCompilation()) {
4387             functionNode.getCompileUnit().addFunctionInitializer(data, functionNode);
4388             initializedFunctionIds.add(fnId);
4389         }
4390 
4391         // We don't emit a ScriptFunction on stack for the outermost compiled function (as there's no code being
4392         // generated in its outer context that'd need it as a callee).
4393         if (lc.getOutermostFunction() == functionNode) {
4394             return;
4395         }
4396 
4397         method._new(SCRIPTFUNCTION_IMPL_NAME, SCRIPTFUNCTION_IMPL_TYPE).dup();
4398         loadConstant(data);
4399 
4400         if (functionNode.needsParentScope()) {
4401             method.loadCompilerConstant(SCOPE);
4402         } else {
4403             method.loadNull();
4404         }
4405         method.invoke(constructorNoLookup(SCRIPTFUNCTION_IMPL_NAME, RecompilableScriptFunctionData.class, ScriptObject.class));
4406     }
4407 
4408     // calls on Global class.
4409     private MethodEmitter globalInstance() {
4410         return method.invokestatic(GLOBAL_OBJECT, "instance", "()L" + GLOBAL_OBJECT + ';');
4411     }
4412 
4413     private MethodEmitter globalAllocateArguments() {
4414         return method.invokestatic(GLOBAL_OBJECT, "allocateArguments", methodDescriptor(ScriptObject.class, Object[].class, Object.class, int.class));
4415     }
4416 
4417     private MethodEmitter globalNewRegExp() {
4418         return method.invokestatic(GLOBAL_OBJECT, "newRegExp", methodDescriptor(Object.class, String.class, String.class));
4419     }
4420 
4421     private MethodEmitter globalRegExpCopy() {
4422         return method.invokestatic(GLOBAL_OBJECT, "regExpCopy", methodDescriptor(Object.class, Object.class));
4423     }
4424 
4425     private MethodEmitter globalAllocateArray(final ArrayType type) {
4426         //make sure the native array is treated as an array type
4427         return method.invokestatic(GLOBAL_OBJECT, "allocate", "(" + type.getDescriptor() + ")Ljdk/nashorn/internal/objects/NativeArray;");
4428     }
4429 
4430     private MethodEmitter globalIsEval() {
4431         return method.invokestatic(GLOBAL_OBJECT, "isEval", methodDescriptor(boolean.class, Object.class));
4432     }
4433 
4434     private MethodEmitter globalReplaceLocationPropertyPlaceholder() {
4435         return method.invokestatic(GLOBAL_OBJECT, "replaceLocationPropertyPlaceholder", methodDescriptor(Object.class, Object.class, Object.class));
4436     }
4437 
4438     private MethodEmitter globalCheckObjectCoercible() {
4439         return method.invokestatic(GLOBAL_OBJECT, "checkObjectCoercible", methodDescriptor(void.class, Object.class));
4440     }
4441 
4442     private MethodEmitter globalDirectEval() {
4443         return method.invokestatic(GLOBAL_OBJECT, "directEval",
4444                 methodDescriptor(Object.class, Object.class, Object.class, Object.class, Object.class, boolean.class));
4445     }
4446 
4447     private abstract class OptimisticOperation {
4448         private final boolean isOptimistic;
4449         // expression and optimistic are the same reference
4450         private final Expression expression;
4451         private final Optimistic optimistic;
4452         private final TypeBounds resultBounds;
4453 
4454         OptimisticOperation(final Optimistic optimistic, final TypeBounds resultBounds) {
4455             this.optimistic = optimistic;
4456             this.expression = (Expression)optimistic;
4457             this.resultBounds = resultBounds;
4458             this.isOptimistic = isOptimistic(optimistic) && useOptimisticTypes() &&
4459                     // Operation is only effectively optimistic if its type, after being coerced into the result bounds
4460                     // is narrower than the upper bound.
4461                     resultBounds.within(Type.generic(((Expression)optimistic).getType())).narrowerThan(resultBounds.widest);
4462         }
4463 
4464         MethodEmitter emit() {
4465             return emit(0);
4466         }
4467 
4468         MethodEmitter emit(final int ignoredArgCount) {
4469             final int     programPoint                  = optimistic.getProgramPoint();
4470             final boolean optimisticOrContinuation      = isOptimistic || isContinuationEntryPoint(programPoint);
4471             final boolean currentContinuationEntryPoint = isCurrentContinuationEntryPoint(programPoint);
4472             final int     stackSizeOnEntry              = method.getStackSize() - ignoredArgCount;
4473 
4474             // First store the values on the stack opportunistically into local variables. Doing it before loadStack()
4475             // allows us to not have to pop/load any arguments that are pushed onto it by loadStack() in the second
4476             // storeStack().
4477             storeStack(ignoredArgCount, optimisticOrContinuation);
4478 
4479             // Now, load the stack
4480             loadStack();
4481 
4482             // Now store the values on the stack ultimately into local variables. In vast majority of cases, this is
4483             // (aside from creating the local types map) a no-op, as the first opportunistic stack store will already
4484             // store all variables. However, there can be operations in the loadStack() that invalidate some of the
4485             // stack stores, e.g. in "x[i] = x[++i]", "++i" will invalidate the already stored value for "i". In such
4486             // unfortunate cases this second storeStack() will restore the invariant that everything on the stack is
4487             // stored into a local variable, although at the cost of doing a store/load on the loaded arguments as well.
4488             final int liveLocalsCount = storeStack(method.getStackSize() - stackSizeOnEntry, optimisticOrContinuation);
4489             assert optimisticOrContinuation == (liveLocalsCount != -1);
4490 
4491             final Label beginTry;
4492             final Label catchLabel;
4493             final Label afterConsumeStack = isOptimistic || currentContinuationEntryPoint ? new Label("after_consume_stack") : null;
4494             if(isOptimistic) {
4495                 beginTry = new Label("try_optimistic");
4496                 final String catchLabelName = (afterConsumeStack == null ? "" : afterConsumeStack.toString()) + "_handler";
4497                 catchLabel = new Label(catchLabelName);
4498                 method.label(beginTry);
4499             } else {
4500                 beginTry = catchLabel = null;
4501             }
4502 
4503             consumeStack();
4504 
4505             if(isOptimistic) {
4506                 method._try(beginTry, afterConsumeStack, catchLabel, UnwarrantedOptimismException.class);
4507             }
4508 
4509             if(isOptimistic || currentContinuationEntryPoint) {
4510                 method.label(afterConsumeStack);
4511 
4512                 final int[] localLoads = method.getLocalLoadsOnStack(0, stackSizeOnEntry);
4513                 assert everyStackValueIsLocalLoad(localLoads) : Arrays.toString(localLoads) + ", " + stackSizeOnEntry + ", " + ignoredArgCount;
4514                 final List<Type> localTypesList = method.getLocalVariableTypes();
4515                 final int usedLocals = method.getUsedSlotsWithLiveTemporaries();
4516                 final List<Type> localTypes = method.getWidestLiveLocals(localTypesList.subList(0, usedLocals));
4517                 assert everyLocalLoadIsValid(localLoads, usedLocals) : Arrays.toString(localLoads) + " ~ " + localTypes;
4518 
4519                 if(isOptimistic) {
4520                     addUnwarrantedOptimismHandlerLabel(localTypes, catchLabel);
4521                 }
4522                 if(currentContinuationEntryPoint) {
4523                     final ContinuationInfo ci = getContinuationInfo();
4524                     assert ci != null : "no continuation info found for " + lc.getCurrentFunction();
4525                     assert !ci.hasTargetLabel(); // No duplicate program points
4526                     ci.setTargetLabel(afterConsumeStack);
4527                     ci.getHandlerLabel().markAsOptimisticContinuationHandlerFor(afterConsumeStack);
4528                     // Can't rely on targetLabel.stack.localVariableTypes.length, as it can be higher due to effectively
4529                     // dead local variables.
4530                     ci.lvarCount = localTypes.size();
4531                     ci.setStackStoreSpec(localLoads);
4532                     ci.setStackTypes(Arrays.copyOf(method.getTypesFromStack(method.getStackSize()), stackSizeOnEntry));
4533                     assert ci.getStackStoreSpec().length == ci.getStackTypes().length;
4534                     ci.setReturnValueType(method.peekType());
4535                     ci.lineNumber = getLastLineNumber();
4536                     ci.catchLabel = catchLabels.peek();
4537                 }
4538             }
4539             return method;
4540         }
4541 
4542         /**
4543          * Stores the current contents of the stack into local variables so they are not lost before invoking something that
4544          * can result in an {@code UnwarantedOptimizationException}.
4545          * @param ignoreArgCount the number of topmost arguments on stack to ignore when deciding on the shape of the catch
4546          * block. Those are used in the situations when we could not place the call to {@code storeStack} early enough
4547          * (before emitting code for pushing the arguments that the optimistic call will pop). This is admittedly a
4548          * deficiency in the design of the code generator when it deals with self-assignments and we should probably look
4549          * into fixing it.
4550          * @return types of the significant local variables after the stack was stored (types for local variables used
4551          * for temporary storage of ignored arguments are not returned).
4552          * @param optimisticOrContinuation if false, this method should not execute
4553          * a label for a catch block for the {@code UnwarantedOptimizationException}, suitable for capturing the
4554          * currently live local variables, tailored to their types.
4555          */
4556         private int storeStack(final int ignoreArgCount, final boolean optimisticOrContinuation) {
4557             if(!optimisticOrContinuation) {
4558                 return -1; // NOTE: correct value to return is lc.getUsedSlotCount(), but it wouldn't be used anyway
4559             }
4560 
4561             final int stackSize = method.getStackSize();
4562             final Type[] stackTypes = method.getTypesFromStack(stackSize);
4563             final int[] localLoadsOnStack = method.getLocalLoadsOnStack(0, stackSize);
4564             final int usedSlots = method.getUsedSlotsWithLiveTemporaries();
4565 
4566             final int firstIgnored = stackSize - ignoreArgCount;
4567             // Find the first value on the stack (from the bottom) that is not a load from a local variable.
4568             int firstNonLoad = 0;
4569             while(firstNonLoad < firstIgnored && localLoadsOnStack[firstNonLoad] != Label.Stack.NON_LOAD) {
4570                 firstNonLoad++;
4571             }
4572 
4573             // Only do the store/load if first non-load is not an ignored argument. Otherwise, do nothing and return
4574             // the number of used slots as the number of live local variables.
4575             if(firstNonLoad >= firstIgnored) {
4576                 return usedSlots;
4577             }
4578 
4579             // Find the number of new temporary local variables that we need; it's the number of values on the stack that
4580             // are not direct loads of existing local variables.
4581             int tempSlotsNeeded = 0;
4582             for(int i = firstNonLoad; i < stackSize; ++i) {
4583                 if(localLoadsOnStack[i] == Label.Stack.NON_LOAD) {
4584                     tempSlotsNeeded += stackTypes[i].getSlots();
4585                 }
4586             }
4587 
4588             // Ensure all values on the stack that weren't directly loaded from a local variable are stored in a local
4589             // variable. We're starting from highest local variable index, so that in case ignoreArgCount > 0 the ignored
4590             // ones end up at the end of the local variable table.
4591             int lastTempSlot = usedSlots + tempSlotsNeeded;
4592             int ignoreSlotCount = 0;
4593             for(int i = stackSize; i -- > firstNonLoad;) {
4594                 final int loadSlot = localLoadsOnStack[i];
4595                 if(loadSlot == Label.Stack.NON_LOAD) {
4596                     final Type type = stackTypes[i];
4597                     final int slots = type.getSlots();
4598                     lastTempSlot -= slots;
4599                     if(i >= firstIgnored) {
4600                         ignoreSlotCount += slots;
4601                     }
4602                     method.storeTemp(type, lastTempSlot);
4603                 } else {
4604                     method.pop();
4605                 }
4606             }
4607             assert lastTempSlot == usedSlots; // used all temporary locals
4608 
4609             final List<Type> localTypesList = method.getLocalVariableTypes();
4610 
4611             // Load values back on stack.
4612             for(int i = firstNonLoad; i < stackSize; ++i) {
4613                 final int loadSlot = localLoadsOnStack[i];
4614                 final Type stackType = stackTypes[i];
4615                 final boolean isLoad = loadSlot != Label.Stack.NON_LOAD;
4616                 final int lvarSlot = isLoad ? loadSlot : lastTempSlot;
4617                 final Type lvarType = localTypesList.get(lvarSlot);
4618                 method.load(lvarType, lvarSlot);
4619                 if(isLoad) {
4620                     // Conversion operators (I2L etc.) preserve "load"-ness of the value despite the fact that, in the
4621                     // strict sense they are creating a derived value from the loaded value. This special behavior of
4622                     // on-stack conversion operators is necessary to accommodate for differences in local variable types
4623                     // after deoptimization; having a conversion operator throw away "load"-ness would create different
4624                     // local variable table shapes between optimism-failed code and its deoptimized rest-of method).
4625                     // After we load the value back, we need to redo the conversion to the stack type if stack type is
4626                     // different.
4627                     // NOTE: this would only strictly be necessary for widening conversions (I2L, L2D, I2D), and not for
4628                     // narrowing ones (L2I, D2L, D2I) as only widening conversions are the ones that can get eliminated
4629                     // in a deoptimized method, as their original input argument got widened. Maybe experiment with
4630                     // throwing away "load"-ness for narrowing conversions in MethodEmitter.convert()?
4631                     method.convert(stackType);
4632                 } else {
4633                     // temporary stores never needs a convert, as their type is always the same as the stack type.
4634                     assert lvarType == stackType;
4635                     lastTempSlot += lvarType.getSlots();
4636                 }
4637             }
4638             // used all temporaries
4639             assert lastTempSlot == usedSlots + tempSlotsNeeded;
4640 
4641             return lastTempSlot - ignoreSlotCount;
4642         }
4643 
4644         private void addUnwarrantedOptimismHandlerLabel(final List<Type> localTypes, final Label label) {
4645             final String lvarTypesDescriptor = getLvarTypesDescriptor(localTypes);
4646             final Map<String, Collection<Label>> unwarrantedOptimismHandlers = lc.getUnwarrantedOptimismHandlers();
4647             Collection<Label> labels = unwarrantedOptimismHandlers.get(lvarTypesDescriptor);
4648             if(labels == null) {
4649                 labels = new LinkedList<>();
4650                 unwarrantedOptimismHandlers.put(lvarTypesDescriptor, labels);
4651             }
4652             method.markLabelAsOptimisticCatchHandler(label, localTypes.size());
4653             labels.add(label);
4654         }
4655 
4656         abstract void loadStack();
4657 
4658         // Make sure that whatever indy call site you emit from this method uses {@code getCallSiteFlagsOptimistic(node)}
4659         // or otherwise ensure optimistic flag is correctly set in the call site, otherwise it doesn't make much sense
4660         // to use OptimisticExpression for emitting it.
4661         abstract void consumeStack();
4662 
4663         /**
4664          * Emits the correct dynamic getter code. Normally just delegates to method emitter, except when the target
4665          * expression is optimistic, and the desired type is narrower than the optimistic type. In that case, it'll emit a
4666          * dynamic getter with its original optimistic type, and explicitly insert a narrowing conversion. This way we can
4667          * preserve the optimism of the values even if they're subsequently immediately coerced into a narrower type. This
4668          * is beneficial because in this case we can still presume that since the original getter was optimistic, the
4669          * conversion has no side effects.
4670          * @param name the name of the property being get
4671          * @param flags call site flags
4672          * @param isMethod whether we're preferrably retrieving a function
4673          * @return the current method emitter
4674          */
4675         MethodEmitter dynamicGet(final String name, final int flags, final boolean isMethod) {
4676             if(isOptimistic) {
4677                 return method.dynamicGet(getOptimisticCoercedType(), name, getOptimisticFlags(flags), isMethod);
4678             }
4679             return method.dynamicGet(resultBounds.within(expression.getType()), name, nonOptimisticFlags(flags), isMethod);
4680         }
4681 
4682         MethodEmitter dynamicGetIndex(final int flags, final boolean isMethod) {
4683             if(isOptimistic) {
4684                 return method.dynamicGetIndex(getOptimisticCoercedType(), getOptimisticFlags(flags), isMethod);
4685             }
4686             return method.dynamicGetIndex(resultBounds.within(expression.getType()), nonOptimisticFlags(flags), isMethod);
4687         }
4688 
4689         MethodEmitter dynamicCall(final int argCount, final int flags) {
4690             if (isOptimistic) {
4691                 return method.dynamicCall(getOptimisticCoercedType(), argCount, getOptimisticFlags(flags));
4692             }
4693             return method.dynamicCall(resultBounds.within(expression.getType()), argCount, nonOptimisticFlags(flags));
4694         }
4695 
4696         int getOptimisticFlags(final int flags) {
4697             return flags | CALLSITE_OPTIMISTIC | (optimistic.getProgramPoint() << CALLSITE_PROGRAM_POINT_SHIFT); //encode program point in high bits
4698         }
4699 
4700         int getProgramPoint() {
4701             return isOptimistic ? optimistic.getProgramPoint() : INVALID_PROGRAM_POINT;
4702         }
4703 
4704         void convertOptimisticReturnValue() {
4705             if (isOptimistic) {
4706                 final Type optimisticType = getOptimisticCoercedType();
4707                 if(!optimisticType.isObject()) {
4708                     method.load(optimistic.getProgramPoint());
4709                     if(optimisticType.isInteger()) {
4710                         method.invoke(ENSURE_INT);
4711                     } else if(optimisticType.isLong()) {
4712                         method.invoke(ENSURE_LONG);
4713                     } else if(optimisticType.isNumber()) {
4714                         method.invoke(ENSURE_NUMBER);
4715                     } else {
4716                         throw new AssertionError(optimisticType);
4717                     }
4718                 }
4719             }
4720         }
4721 
4722         void replaceCompileTimeProperty() {
4723             final IdentNode identNode = (IdentNode)expression;
4724             final String name = identNode.getSymbol().getName();
4725             if (CompilerConstants.__FILE__.name().equals(name)) {
4726                 replaceCompileTimeProperty(getCurrentSource().getName());
4727             } else if (CompilerConstants.__DIR__.name().equals(name)) {
4728                 replaceCompileTimeProperty(getCurrentSource().getBase());
4729             } else if (CompilerConstants.__LINE__.name().equals(name)) {
4730                 replaceCompileTimeProperty(getCurrentSource().getLine(identNode.position()));
4731             }
4732         }
4733 
4734         /**
4735          * When an ident with name __FILE__, __DIR__, or __LINE__ is loaded, we'll try to look it up as any other
4736          * identifier. However, if it gets all the way up to the Global object, it will send back a special value that
4737          * represents a placeholder for these compile-time location properties. This method will generate code that loads
4738          * the value of the compile-time location property and then invokes a method in Global that will replace the
4739          * placeholder with the value. Effectively, if the symbol for these properties is defined anywhere in the lexical
4740          * scope, they take precedence, but if they aren't, then they resolve to the compile-time location property.
4741          * @param propertyValue the actual value of the property
4742          */
4743         private void replaceCompileTimeProperty(final Object propertyValue) {
4744             assert method.peekType().isObject();
4745             if(propertyValue instanceof String || propertyValue == null) {
4746                 method.load((String)propertyValue);
4747             } else if(propertyValue instanceof Integer) {
4748                 method.load(((Integer)propertyValue).intValue());
4749                 method.convert(Type.OBJECT);
4750             } else {
4751                 throw new AssertionError();
4752             }
4753             globalReplaceLocationPropertyPlaceholder();
4754             convertOptimisticReturnValue();
4755         }
4756 
4757         /**
4758          * Returns the type that should be used as the return type of the dynamic invocation that is emitted as the code
4759          * for the current optimistic operation. If the type bounds is exact boolean or narrower than the expression's
4760          * optimistic type, then the optimistic type is returned, otherwise the coercing type. Effectively, this method
4761          * allows for moving the coercion into the optimistic type when it won't adversely affect the optimistic
4762          * evaluation semantics, and for preserving the optimistic type and doing a separate coercion when it would
4763          * affect it.
4764          * @return
4765          */
4766         private Type getOptimisticCoercedType() {
4767             final Type optimisticType = expression.getType();
4768             assert resultBounds.widest.widerThan(optimisticType);
4769             final Type narrowest = resultBounds.narrowest;
4770 
4771             if(narrowest.isBoolean() || narrowest.narrowerThan(optimisticType)) {
4772                 assert !optimisticType.isObject();
4773                 return optimisticType;
4774             }
4775             assert !narrowest.isObject();
4776             return narrowest;
4777         }
4778     }
4779 
4780     private static boolean isOptimistic(final Optimistic optimistic) {
4781         if(!optimistic.canBeOptimistic()) {
4782             return false;
4783         }
4784         final Expression expr = (Expression)optimistic;
4785         return expr.getType().narrowerThan(expr.getWidestOperationType());
4786     }
4787 
4788     private static boolean everyLocalLoadIsValid(final int[] loads, final int localCount) {
4789         for (final int load : loads) {
4790             if(load < 0 || load >= localCount) {
4791                 return false;
4792             }
4793         }
4794         return true;
4795     }
4796 
4797     private static boolean everyStackValueIsLocalLoad(final int[] loads) {
4798         for (final int load : loads) {
4799             if(load == Label.Stack.NON_LOAD) {
4800                 return false;
4801             }
4802         }
4803         return true;
4804     }
4805 
4806     private String getLvarTypesDescriptor(final List<Type> localVarTypes) {
4807         final int count = localVarTypes.size();
4808         final StringBuilder desc = new StringBuilder(count);
4809         for(int i = 0; i < count;) {
4810             i += appendType(desc, localVarTypes.get(i));
4811         }
4812         return method.markSymbolBoundariesInLvarTypesDescriptor(desc.toString());
4813     }
4814 
4815     private static int appendType(final StringBuilder b, final Type t) {
4816         b.append(t.getBytecodeStackType());
4817         return t.getSlots();
4818     }
4819 
4820     private static int countSymbolsInLvarTypeDescriptor(final String lvarTypeDescriptor) {
4821         int count = 0;
4822         for(int i = 0; i < lvarTypeDescriptor.length(); ++i) {
4823             if(Character.isUpperCase(lvarTypeDescriptor.charAt(i))) {
4824                 ++count;
4825             }
4826         }
4827         return count;
4828 
4829     }
4830     /**
4831      * Generates all the required {@code UnwarrantedOptimismException} handlers for the current function. The employed
4832      * strategy strives to maximize code reuse. Every handler constructs an array to hold the local variables, then
4833      * fills in some trailing part of the local variables (those for which it has a unique suffix in the descriptor),
4834      * then jumps to a handler for a prefix that's shared with other handlers. A handler that fills up locals up to
4835      * position 0 will not jump to a prefix handler (as it has no prefix), but instead end with constructing and
4836      * throwing a {@code RewriteException}. Since we lexicographically sort the entries, we only need to check every
4837      * entry to its immediately preceding one for longest matching prefix.
4838      * @return true if there is at least one exception handler
4839      */
4840     private boolean generateUnwarrantedOptimismExceptionHandlers(final FunctionNode fn) {
4841         if(!useOptimisticTypes()) {
4842             return false;
4843         }
4844 
4845         // Take the mapping of lvarSpecs -> labels, and turn them into a descending lexicographically sorted list of
4846         // handler specifications.
4847         final Map<String, Collection<Label>> unwarrantedOptimismHandlers = lc.popUnwarrantedOptimismHandlers();
4848         if(unwarrantedOptimismHandlers.isEmpty()) {
4849             return false;
4850         }
4851 
4852         method.lineNumber(0);
4853 
4854         final List<OptimismExceptionHandlerSpec> handlerSpecs = new ArrayList<>(unwarrantedOptimismHandlers.size() * 4/3);
4855         for(final String spec: unwarrantedOptimismHandlers.keySet()) {
4856             handlerSpecs.add(new OptimismExceptionHandlerSpec(spec, true));
4857         }
4858         Collections.sort(handlerSpecs, Collections.reverseOrder());
4859 
4860         // Map of local variable specifications to labels for populating the array for that local variable spec.
4861         final Map<String, Label> delegationLabels = new HashMap<>();
4862 
4863         // Do everything in a single pass over the handlerSpecs list. Note that the list can actually grow as we're
4864         // passing through it as we might add new prefix handlers into it, so can't hoist size() outside of the loop.
4865         for(int handlerIndex = 0; handlerIndex < handlerSpecs.size(); ++handlerIndex) {
4866             final OptimismExceptionHandlerSpec spec = handlerSpecs.get(handlerIndex);
4867             final String lvarSpec = spec.lvarSpec;
4868             if(spec.catchTarget) {
4869                 assert !method.isReachable();
4870                 // Start a catch block and assign the labels for this lvarSpec with it.
4871                 method._catch(unwarrantedOptimismHandlers.get(lvarSpec));
4872                 // This spec is a catch target, so emit array creation code. The length of the array is the number of
4873                 // symbols - the number of uppercase characters.
4874                 method.load(countSymbolsInLvarTypeDescriptor(lvarSpec));
4875                 method.newarray(Type.OBJECT_ARRAY);
4876             }
4877             if(spec.delegationTarget) {
4878                 // If another handler can delegate to this handler as its prefix, then put a jump target here for the
4879                 // shared code (after the array creation code, which is never shared).
4880                 method.label(delegationLabels.get(lvarSpec)); // label must exist
4881             }
4882 
4883             final boolean lastHandler = handlerIndex == handlerSpecs.size() - 1;
4884 
4885             int lvarIndex;
4886             final int firstArrayIndex;
4887             final int firstLvarIndex;
4888             Label delegationLabel;
4889             final String commonLvarSpec;
4890             if(lastHandler) {
4891                 // Last handler block, doesn't delegate to anything.
4892                 lvarIndex = 0;
4893                 firstLvarIndex = 0;
4894                 firstArrayIndex = 0;
4895                 delegationLabel = null;
4896                 commonLvarSpec = null;
4897             } else {
4898                 // Not yet the last handler block, will definitely delegate to another handler; let's figure out which
4899                 // one. It can be an already declared handler further down the list, or it might need to declare a new
4900                 // prefix handler.
4901 
4902                 // Since we're lexicographically ordered, the common prefix handler is defined by the common prefix of
4903                 // this handler and the next handler on the list.
4904                 final int nextHandlerIndex = handlerIndex + 1;
4905                 final String nextLvarSpec = handlerSpecs.get(nextHandlerIndex).lvarSpec;
4906                 commonLvarSpec = commonPrefix(lvarSpec, nextLvarSpec);
4907                 // We don't chop symbols in half
4908                 assert Character.isUpperCase(commonLvarSpec.charAt(commonLvarSpec.length() - 1));
4909 
4910                 // Let's find if we already have a declaration for such handler, or we need to insert it.
4911                 {
4912                     boolean addNewHandler = true;
4913                     int commonHandlerIndex = nextHandlerIndex;
4914                     for(; commonHandlerIndex < handlerSpecs.size(); ++commonHandlerIndex) {
4915                         final OptimismExceptionHandlerSpec forwardHandlerSpec = handlerSpecs.get(commonHandlerIndex);
4916                         final String forwardLvarSpec = forwardHandlerSpec.lvarSpec;
4917                         if(forwardLvarSpec.equals(commonLvarSpec)) {
4918                             // We already have a handler for the common prefix.
4919                             addNewHandler = false;
4920                             // Make sure we mark it as a delegation target.
4921                             forwardHandlerSpec.delegationTarget = true;
4922                             break;
4923                         } else if(!forwardLvarSpec.startsWith(commonLvarSpec)) {
4924                             break;
4925                         }
4926                     }
4927                     if(addNewHandler) {
4928                         // We need to insert a common prefix handler. Note handlers created with catchTarget == false
4929                         // will automatically have delegationTarget == true (because that's the only reason for their
4930                         // existence).
4931                         handlerSpecs.add(commonHandlerIndex, new OptimismExceptionHandlerSpec(commonLvarSpec, false));
4932                     }
4933                 }
4934 
4935                 firstArrayIndex = countSymbolsInLvarTypeDescriptor(commonLvarSpec);
4936                 lvarIndex = 0;
4937                 for(int j = 0; j < commonLvarSpec.length(); ++j) {
4938                     lvarIndex += CodeGeneratorLexicalContext.getTypeForSlotDescriptor(commonLvarSpec.charAt(j)).getSlots();
4939                 }
4940                 firstLvarIndex = lvarIndex;
4941 
4942                 // Create a delegation label if not already present
4943                 delegationLabel = delegationLabels.get(commonLvarSpec);
4944                 if(delegationLabel == null) {
4945                     // uo_pa == "unwarranted optimism, populate array"
4946                     delegationLabel = new Label("uo_pa_" + commonLvarSpec);
4947                     delegationLabels.put(commonLvarSpec, delegationLabel);
4948                 }
4949             }
4950 
4951             // Load local variables handled by this handler on stack
4952             int args = 0;
4953             boolean symbolHadValue = false;
4954             for(int typeIndex = commonLvarSpec == null ? 0 : commonLvarSpec.length(); typeIndex < lvarSpec.length(); ++typeIndex) {
4955                 final char typeDesc = lvarSpec.charAt(typeIndex);
4956                 final Type lvarType = CodeGeneratorLexicalContext.getTypeForSlotDescriptor(typeDesc);
4957                 if (!lvarType.isUnknown()) {
4958                     method.load(lvarType, lvarIndex);
4959                     symbolHadValue = true;
4960                     args++;
4961                 } else if(typeDesc == 'U' && !symbolHadValue) {
4962                     // Symbol boundary with undefined last value. Check if all previous values for this symbol were also
4963                     // undefined; if so, emit one explicit Undefined. This serves to ensure that we're emiting exactly
4964                     // one value for every symbol that uses local slots. While we could in theory ignore symbols that
4965                     // are undefined (in other words, dead) at the point where this exception was thrown, unfortunately
4966                     // we can't do it in practice. The reason for this is that currently our liveness analysis is
4967                     // coarse (it can determine whether a symbol has not been read with a particular type anywhere in
4968                     // the function being compiled, but that's it), and a symbol being promoted to Object due to a
4969                     // deoptimization will suddenly show up as "live for Object type", and previously dead U->O
4970                     // conversions on loop entries will suddenly become alive in the deoptimized method which will then
4971                     // expect a value for that slot in its continuation handler. If we had precise liveness analysis, we
4972                     // could go back to excluding known dead symbols from the payload of the RewriteException.
4973                     if(method.peekType() == Type.UNDEFINED) {
4974                         method.dup();
4975                     } else {
4976                         method.loadUndefined(Type.OBJECT);
4977                     }
4978                     args++;
4979                 }
4980                 if(Character.isUpperCase(typeDesc)) {
4981                     // Reached symbol boundary; reset flag for the next symbol.
4982                     symbolHadValue = false;
4983                 }
4984                 lvarIndex += lvarType.getSlots();
4985             }
4986             assert args > 0;
4987             // Delegate actual storing into array to an array populator utility method.
4988             //on the stack:
4989             // object array to be populated
4990             // start index
4991             // a lot of types
4992             method.dynamicArrayPopulatorCall(args + 1, firstArrayIndex);
4993             if(delegationLabel != null) {
4994                 // We cascade to a prefix handler to fill out the rest of the local variables and throw the
4995                 // RewriteException.
4996                 assert !lastHandler;
4997                 assert commonLvarSpec != null;
4998                 // Must undefine the local variables that we have already processed for the sake of correct join on the
4999                 // delegate label
5000                 method.undefineLocalVariables(firstLvarIndex, true);
5001                 final OptimismExceptionHandlerSpec nextSpec = handlerSpecs.get(handlerIndex + 1);
5002                 // If the delegate immediately follows, and it's not a catch target (so it doesn't have array setup
5003                 // code) don't bother emitting a jump, as we'd just jump to the next instruction.
5004                 if(!nextSpec.lvarSpec.equals(commonLvarSpec) || nextSpec.catchTarget) {
5005                     method._goto(delegationLabel);
5006                 }
5007             } else {
5008                 assert lastHandler;
5009                 // Nothing to delegate to, so this handler must create and throw the RewriteException.
5010                 // At this point we have the UnwarrantedOptimismException and the Object[] with local variables on
5011                 // stack. We need to create a RewriteException, push two references to it below the constructor
5012                 // arguments, invoke the constructor, and throw the exception.
5013                 loadConstant(getByteCodeSymbolNames(fn));
5014                 if (isRestOf()) {
5015                     loadConstant(getContinuationEntryPoints());
5016                     method.invoke(CREATE_REWRITE_EXCEPTION_REST_OF);
5017                 } else {
5018                     method.invoke(CREATE_REWRITE_EXCEPTION);
5019                 }
5020                 method.athrow();
5021             }
5022         }
5023         return true;
5024     }
5025 
5026     private static String[] getByteCodeSymbolNames(final FunctionNode fn) {
5027         // Only names of local variables on the function level are captured. This information is used to reduce
5028         // deoptimizations, so as much as we can capture will help. We rely on the fact that function wide variables are
5029         // all live all the time, so the array passed to rewrite exception contains one element for every slotted symbol
5030         // here.
5031         final List<String> names = new ArrayList<>();
5032         for (final Symbol symbol: fn.getBody().getSymbols()) {
5033             if (symbol.hasSlot()) {
5034                 if (symbol.isScope()) {
5035                     // slot + scope can only be true for parameters
5036                     assert symbol.isParam();
5037                     names.add(null);
5038                 } else {
5039                     names.add(symbol.getName());
5040                 }
5041             }
5042         }
5043         return names.toArray(new String[names.size()]);
5044     }
5045 
5046     private static String commonPrefix(final String s1, final String s2) {
5047         final int l1 = s1.length();
5048         final int l = Math.min(l1, s2.length());
5049         int lms = -1; // last matching symbol
5050         for(int i = 0; i < l; ++i) {
5051             final char c1 = s1.charAt(i);
5052             if(c1 != s2.charAt(i)) {
5053                 return s1.substring(0, lms + 1);
5054             } else if(Character.isUpperCase(c1)) {
5055                 lms = i;
5056             }
5057         }
5058         return l == l1 ? s1 : s2;
5059     }
5060 
5061     private static class OptimismExceptionHandlerSpec implements Comparable<OptimismExceptionHandlerSpec> {
5062         private final String lvarSpec;
5063         private final boolean catchTarget;
5064         private boolean delegationTarget;
5065 
5066         OptimismExceptionHandlerSpec(final String lvarSpec, final boolean catchTarget) {
5067             this.lvarSpec = lvarSpec;
5068             this.catchTarget = catchTarget;
5069             if(!catchTarget) {
5070                 delegationTarget = true;
5071             }
5072         }
5073 
5074         @Override
5075         public int compareTo(final OptimismExceptionHandlerSpec o) {
5076             return lvarSpec.compareTo(o.lvarSpec);
5077         }
5078 
5079         @Override
5080         public String toString() {
5081             final StringBuilder b = new StringBuilder(64).append("[HandlerSpec ").append(lvarSpec);
5082             if(catchTarget) {
5083                 b.append(", catchTarget");
5084             }
5085             if(delegationTarget) {
5086                 b.append(", delegationTarget");
5087             }
5088             return b.append("]").toString();
5089         }
5090     }
5091 
5092     private static class ContinuationInfo {
5093         private final Label handlerLabel;
5094         private Label targetLabel; // Label for the target instruction.
5095         int lvarCount;
5096         // Indices of local variables that need to be loaded on the stack when this node completes
5097         private int[] stackStoreSpec;
5098         // Types of values loaded on the stack
5099         private Type[] stackTypes;
5100         // If non-null, this node should perform the requisite type conversion
5101         private Type returnValueType;
5102         // If we are in the middle of an object literal initialization, we need to update the map
5103         private PropertyMap objectLiteralMap;
5104         // Object literal stack depth for object literal - not necessarly top if property is a tree
5105         private int objectLiteralStackDepth = -1;
5106         // The line number at the continuation point
5107         private int lineNumber;
5108         // The active catch label, in case the continuation point is in a try/catch block
5109         private Label catchLabel;
5110         // The number of scopes that need to be popped before control is transferred to the catch label.
5111         private int exceptionScopePops;
5112 
5113         ContinuationInfo() {
5114             this.handlerLabel = new Label("continuation_handler");
5115         }
5116 
5117         Label getHandlerLabel() {
5118             return handlerLabel;
5119         }
5120 
5121         boolean hasTargetLabel() {
5122             return targetLabel != null;
5123         }
5124 
5125         Label getTargetLabel() {
5126             return targetLabel;
5127         }
5128 
5129         void setTargetLabel(final Label targetLabel) {
5130             this.targetLabel = targetLabel;
5131         }
5132 
5133         int[] getStackStoreSpec() {
5134             return stackStoreSpec.clone();
5135         }
5136 
5137         void setStackStoreSpec(final int[] stackStoreSpec) {
5138             this.stackStoreSpec = stackStoreSpec;
5139         }
5140 
5141         Type[] getStackTypes() {
5142             return stackTypes.clone();
5143         }
5144 
5145         void setStackTypes(final Type[] stackTypes) {
5146             this.stackTypes = stackTypes;
5147         }
5148 
5149         Type getReturnValueType() {
5150             return returnValueType;
5151         }
5152 
5153         void setReturnValueType(final Type returnValueType) {
5154             this.returnValueType = returnValueType;
5155         }
5156 
5157         int getObjectLiteralStackDepth() {
5158             return objectLiteralStackDepth;
5159         }
5160 
5161         void setObjectLiteralStackDepth(final int objectLiteralStackDepth) {
5162             this.objectLiteralStackDepth = objectLiteralStackDepth;
5163         }
5164 
5165         PropertyMap getObjectLiteralMap() {
5166             return objectLiteralMap;
5167         }
5168 
5169         void setObjectLiteralMap(final PropertyMap objectLiteralMap) {
5170             this.objectLiteralMap = objectLiteralMap;
5171         }
5172 
5173         @Override
5174         public String toString() {
5175              return "[localVariableTypes=" + targetLabel.getStack().getLocalVariableTypesCopy() + ", stackStoreSpec=" +
5176                      Arrays.toString(stackStoreSpec) + ", returnValueType=" + returnValueType + "]";
5177         }
5178     }
5179 
5180     private ContinuationInfo getContinuationInfo() {
5181         return fnIdToContinuationInfo.get(lc.getCurrentFunction().getId());
5182     }
5183 
5184     private void generateContinuationHandler() {
5185         if (!isRestOf()) {
5186             return;
5187         }
5188 
5189         final ContinuationInfo ci = getContinuationInfo();
5190         method.label(ci.getHandlerLabel());
5191 
5192         // There should never be an exception thrown from the continuation handler, but in case there is (meaning,
5193         // Nashorn has a bug), then line number 0 will be an indication of where it came from (line numbers are Uint16).
5194         method.lineNumber(0);
5195 
5196         final Label.Stack stack = ci.getTargetLabel().getStack();
5197         final List<Type> lvarTypes = stack.getLocalVariableTypesCopy();
5198         final BitSet symbolBoundary = stack.getSymbolBoundaryCopy();
5199         final int lvarCount = ci.lvarCount;
5200 
5201         final Type rewriteExceptionType = Type.typeFor(RewriteException.class);
5202         // Store the RewriteException into an unused local variable slot.
5203         method.load(rewriteExceptionType, 0);
5204         method.storeTemp(rewriteExceptionType, lvarCount);
5205         // Get local variable array
5206         method.load(rewriteExceptionType, 0);
5207         method.invoke(RewriteException.GET_BYTECODE_SLOTS);
5208         // Store local variables. Note that deoptimization might introduce new value types for existing local variables,
5209         // so we must use both liveLocals and symbolBoundary, as in some cases (when the continuation is inside of a try
5210         // block) we need to store the incoming value into multiple slots. The optimism exception handlers will have
5211         // exactly one array element for every symbol that uses bytecode storage. If in the originating method the value
5212         // was undefined, there will be an explicit Undefined value in the array.
5213         int arrayIndex = 0;
5214         for(int lvarIndex = 0; lvarIndex < lvarCount;) {
5215             final Type lvarType = lvarTypes.get(lvarIndex);
5216             if(!lvarType.isUnknown()) {
5217                 method.dup();
5218                 method.load(arrayIndex).arrayload();
5219                 final Class<?> typeClass = lvarType.getTypeClass();
5220                 // Deoptimization in array initializers can cause arrays to undergo component type widening
5221                 if(typeClass == long[].class) {
5222                     method.load(rewriteExceptionType, lvarCount);
5223                     method.invoke(RewriteException.TO_LONG_ARRAY);
5224                 } else if(typeClass == double[].class) {
5225                     method.load(rewriteExceptionType, lvarCount);
5226                     method.invoke(RewriteException.TO_DOUBLE_ARRAY);
5227                 } else if(typeClass == Object[].class) {
5228                     method.load(rewriteExceptionType, lvarCount);
5229                     method.invoke(RewriteException.TO_OBJECT_ARRAY);
5230                 } else {
5231                     if(!(typeClass.isPrimitive() || typeClass == Object.class)) {
5232                         // NOTE: this can only happen with dead stores. E.g. for the program "1; []; f();" in which the
5233                         // call to f() will deoptimize the call site, but it'll expect :return to have the type
5234                         // NativeArray. However, in the more optimal version, :return's only live type is int, therefore
5235                         // "{O}:return = []" is a dead store, and the variable will be sent into the continuation as
5236                         // Undefined, however NativeArray can't hold Undefined instance.
5237                         method.loadType(Type.getInternalName(typeClass));
5238                         method.invoke(RewriteException.INSTANCE_OR_NULL);
5239                     }
5240                     method.convert(lvarType);
5241                 }
5242                 method.storeHidden(lvarType, lvarIndex, false);
5243             }
5244             final int nextLvarIndex = lvarIndex + lvarType.getSlots();
5245             if(symbolBoundary.get(nextLvarIndex - 1)) {
5246                 ++arrayIndex;
5247             }
5248             lvarIndex = nextLvarIndex;
5249         }
5250         if(assertsEnabled) {
5251             method.load(arrayIndex);
5252             method.invoke(RewriteException.ASSERT_ARRAY_LENGTH);
5253         } else {
5254             method.pop();
5255         }
5256 
5257         final int[]   stackStoreSpec = ci.getStackStoreSpec();
5258         final Type[]  stackTypes     = ci.getStackTypes();
5259         final boolean isStackEmpty   = stackStoreSpec.length == 0;
5260         boolean replacedObjectLiteralMap = false;
5261         if(!isStackEmpty) {
5262             // Load arguments on the stack
5263             final int objectLiteralStackDepth = ci.getObjectLiteralStackDepth();
5264             for(int i = 0; i < stackStoreSpec.length; ++i) {
5265                 final int slot = stackStoreSpec[i];
5266                 method.load(lvarTypes.get(slot), slot);
5267                 method.convert(stackTypes[i]);
5268                 // stack: s0=object literal being initialized
5269                 // change map of s0 so that the property we are initilizing when we failed
5270                 // is now ci.returnValueType
5271                 if (i == objectLiteralStackDepth) {
5272                     method.dup();
5273                     assert ci.getObjectLiteralMap() != null;
5274                     assert ScriptObject.class.isAssignableFrom(method.peekType().getTypeClass()) : method.peekType().getTypeClass() + " is not a script object";
5275                     loadConstant(ci.getObjectLiteralMap());
5276                     method.invoke(ScriptObject.SET_MAP);
5277                     replacedObjectLiteralMap = true;
5278                 }
5279             }
5280         }
5281         // Must have emitted the code for replacing the map of an object literal if we have a set object literal stack depth
5282         assert ci.getObjectLiteralStackDepth() == -1 || replacedObjectLiteralMap;
5283         // Load RewriteException back.
5284         method.load(rewriteExceptionType, lvarCount);
5285         // Get rid of the stored reference
5286         method.loadNull();
5287         method.storeHidden(Type.OBJECT, lvarCount);
5288         // Mark it dead
5289         method.markDeadSlots(lvarCount, Type.OBJECT.getSlots());
5290 
5291         // Load return value on the stack
5292         method.invoke(RewriteException.GET_RETURN_VALUE);
5293 
5294         final Type returnValueType = ci.getReturnValueType();
5295 
5296         // Set up an exception handler for primitive type conversion of return value if needed
5297         boolean needsCatch = false;
5298         final Label targetCatchLabel = ci.catchLabel;
5299         Label _try = null;
5300         if(returnValueType.isPrimitive()) {
5301             // If the conversion throws an exception, we want to report the line number of the continuation point.
5302             method.lineNumber(ci.lineNumber);
5303 
5304             if(targetCatchLabel != METHOD_BOUNDARY) {
5305                 _try = new Label("");
5306                 method.label(_try);
5307                 needsCatch = true;
5308             }
5309         }
5310 
5311         // Convert return value
5312         method.convert(returnValueType);
5313 
5314         final int scopePopCount = needsCatch ? ci.exceptionScopePops : 0;
5315 
5316         // Declare a try/catch for the conversion. If no scopes need to be popped until the target catch block, just
5317         // jump into it. Otherwise, we'll need to create a scope-popping catch block below.
5318         final Label catchLabel = scopePopCount > 0 ? new Label("") : targetCatchLabel;
5319         if(needsCatch) {
5320             final Label _end_try = new Label("");
5321             method.label(_end_try);
5322             method._try(_try, _end_try, catchLabel);
5323         }
5324 
5325         // Jump to continuation point
5326         method._goto(ci.getTargetLabel());
5327 
5328         // Make a scope-popping exception delegate if needed
5329         if(catchLabel != targetCatchLabel) {
5330             method.lineNumber(0);
5331             assert scopePopCount > 0;
5332             method._catch(catchLabel);
5333             popScopes(scopePopCount);
5334             method.uncheckedGoto(targetCatchLabel);
5335         }
5336     }
5337 }
--- EOF ---