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.SCOPE;
  38 import static jdk.nashorn.internal.codegen.CompilerConstants.SPLIT_PREFIX;
  39 import static jdk.nashorn.internal.codegen.CompilerConstants.THIS;
  40 import static jdk.nashorn.internal.codegen.CompilerConstants.VARARGS;
  41 import static jdk.nashorn.internal.codegen.CompilerConstants.constructorNoLookup;
  42 import static jdk.nashorn.internal.codegen.CompilerConstants.interfaceCallNoLookup;
  43 import static jdk.nashorn.internal.codegen.CompilerConstants.methodDescriptor;
  44 import static jdk.nashorn.internal.codegen.CompilerConstants.staticCallNoLookup;
  45 import static jdk.nashorn.internal.codegen.CompilerConstants.typeDescriptor;
  46 import static jdk.nashorn.internal.codegen.CompilerConstants.virtualCallNoLookup;
  47 import static jdk.nashorn.internal.codegen.ObjectClassGenerator.OBJECT_FIELDS_ONLY;
  48 import static jdk.nashorn.internal.ir.Symbol.HAS_SLOT;
  49 import static jdk.nashorn.internal.ir.Symbol.IS_INTERNAL;
  50 import static jdk.nashorn.internal.runtime.UnwarrantedOptimismException.INVALID_PROGRAM_POINT;
  51 import static jdk.nashorn.internal.runtime.UnwarrantedOptimismException.isValid;
  52 import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_APPLY_TO_CALL;
  53 import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_DECLARE;
  54 import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_FAST_SCOPE;
  55 import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_OPTIMISTIC;
  56 import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_PROGRAM_POINT_SHIFT;
  57 import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_SCOPE;
  58 
  59 import java.io.PrintWriter;
  60 import java.util.ArrayDeque;
  61 import java.util.ArrayList;
  62 import java.util.Arrays;
  63 import java.util.BitSet;
  64 import java.util.Collection;
  65 import java.util.Collections;
  66 import java.util.Deque;
  67 import java.util.EnumSet;
  68 import java.util.HashMap;
  69 import java.util.HashSet;
  70 import java.util.Iterator;
  71 import java.util.LinkedList;
  72 import java.util.List;
  73 import java.util.Map;
  74 import java.util.Set;
  75 import java.util.TreeMap;
  76 import java.util.function.Supplier;
  77 import jdk.nashorn.internal.AssertsEnabled;
  78 import jdk.nashorn.internal.IntDeque;
  79 import jdk.nashorn.internal.codegen.ClassEmitter.Flag;
  80 import jdk.nashorn.internal.codegen.CompilerConstants.Call;
  81 import jdk.nashorn.internal.codegen.types.ArrayType;
  82 import jdk.nashorn.internal.codegen.types.Type;
  83 import jdk.nashorn.internal.ir.AccessNode;
  84 import jdk.nashorn.internal.ir.BaseNode;
  85 import jdk.nashorn.internal.ir.BinaryNode;
  86 import jdk.nashorn.internal.ir.Block;
  87 import jdk.nashorn.internal.ir.BlockStatement;
  88 import jdk.nashorn.internal.ir.BreakNode;
  89 import jdk.nashorn.internal.ir.BreakableNode;
  90 import jdk.nashorn.internal.ir.CallNode;
  91 import jdk.nashorn.internal.ir.CaseNode;
  92 import jdk.nashorn.internal.ir.CatchNode;
  93 import jdk.nashorn.internal.ir.ContinueNode;
  94 import jdk.nashorn.internal.ir.EmptyNode;
  95 import jdk.nashorn.internal.ir.Expression;
  96 import jdk.nashorn.internal.ir.ExpressionStatement;
  97 import jdk.nashorn.internal.ir.ForNode;
  98 import jdk.nashorn.internal.ir.FunctionNode;
  99 import jdk.nashorn.internal.ir.FunctionNode.CompilationState;
 100 import jdk.nashorn.internal.ir.GetSplitState;
 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.JoinPredecessorExpression;
 105 import jdk.nashorn.internal.ir.JumpStatement;
 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.SetSplitState;
 123 import jdk.nashorn.internal.ir.SplitReturn;
 124 import jdk.nashorn.internal.ir.Statement;
 125 import jdk.nashorn.internal.ir.SwitchNode;
 126 import jdk.nashorn.internal.ir.Symbol;
 127 import jdk.nashorn.internal.ir.TernaryNode;
 128 import jdk.nashorn.internal.ir.ThrowNode;
 129 import jdk.nashorn.internal.ir.TryNode;
 130 import jdk.nashorn.internal.ir.UnaryNode;
 131 import jdk.nashorn.internal.ir.VarNode;
 132 import jdk.nashorn.internal.ir.WhileNode;
 133 import jdk.nashorn.internal.ir.WithNode;
 134 import jdk.nashorn.internal.ir.visitor.NodeOperatorVisitor;
 135 import jdk.nashorn.internal.ir.visitor.NodeVisitor;
 136 import jdk.nashorn.internal.objects.Global;
 137 import jdk.nashorn.internal.objects.ScriptFunctionImpl;
 138 import jdk.nashorn.internal.parser.Lexer.RegexToken;
 139 import jdk.nashorn.internal.parser.TokenType;
 140 import jdk.nashorn.internal.runtime.Context;
 141 import jdk.nashorn.internal.runtime.Debug;
 142 import jdk.nashorn.internal.runtime.ECMAException;
 143 import jdk.nashorn.internal.runtime.JSType;
 144 import jdk.nashorn.internal.runtime.OptimisticReturnFilters;
 145 import jdk.nashorn.internal.runtime.PropertyMap;
 146 import jdk.nashorn.internal.runtime.RecompilableScriptFunctionData;
 147 import jdk.nashorn.internal.runtime.RewriteException;
 148 import jdk.nashorn.internal.runtime.Scope;
 149 import jdk.nashorn.internal.runtime.ScriptEnvironment;
 150 import jdk.nashorn.internal.runtime.ScriptFunction;
 151 import jdk.nashorn.internal.runtime.ScriptObject;
 152 import jdk.nashorn.internal.runtime.ScriptRuntime;
 153 import jdk.nashorn.internal.runtime.Source;
 154 import jdk.nashorn.internal.runtime.Undefined;
 155 import jdk.nashorn.internal.runtime.UnwarrantedOptimismException;
 156 import jdk.nashorn.internal.runtime.arrays.ArrayData;
 157 import jdk.nashorn.internal.runtime.linker.LinkerCallSite;
 158 import jdk.nashorn.internal.runtime.logging.DebugLogger;
 159 import jdk.nashorn.internal.runtime.logging.Loggable;
 160 import jdk.nashorn.internal.runtime.logging.Logger;
 161 import jdk.nashorn.internal.runtime.options.Options;
 162 
 163 /**
 164  * This is the lowest tier of the code generator. It takes lowered ASTs emitted
 165  * from Lower and emits Java byte code. The byte code emission logic is broken
 166  * out into MethodEmitter. MethodEmitter works internally with a type stack, and
 167  * keeps track of the contents of the byte code stack. This way we avoid a large
 168  * number of special cases on the form
 169  * <pre>
 170  * if (type == INT) {
 171  *     visitInsn(ILOAD, slot);
 172  * } else if (type == DOUBLE) {
 173  *     visitInsn(DOUBLE, slot);
 174  * }
 175  * </pre>
 176  * This quickly became apparent when the code generator was generalized to work
 177  * with all types, and not just numbers or objects.
 178  * <p>
 179  * The CodeGenerator visits nodes only once, tags them as resolved and emits
 180  * bytecode for them.
 181  */
 182 @Logger(name="codegen")
 183 final class CodeGenerator extends NodeOperatorVisitor<CodeGeneratorLexicalContext> implements Loggable {
 184 
 185     private static final Type SCOPE_TYPE = Type.typeFor(ScriptObject.class);
 186 
 187     private static final String GLOBAL_OBJECT = Type.getInternalName(Global.class);
 188 
 189     private static final String SCRIPTFUNCTION_IMPL_NAME = Type.getInternalName(ScriptFunctionImpl.class);
 190     private static final Type   SCRIPTFUNCTION_IMPL_TYPE   = Type.typeFor(ScriptFunction.class);
 191 
 192     private static final Call CREATE_REWRITE_EXCEPTION = CompilerConstants.staticCallNoLookup(RewriteException.class,
 193             "create", RewriteException.class, UnwarrantedOptimismException.class, Object[].class, String[].class);
 194     private static final Call CREATE_REWRITE_EXCEPTION_REST_OF = CompilerConstants.staticCallNoLookup(RewriteException.class,
 195             "create", RewriteException.class, UnwarrantedOptimismException.class, Object[].class, String[].class, int[].class);
 196 
 197     private static final Call ENSURE_INT = CompilerConstants.staticCallNoLookup(OptimisticReturnFilters.class,
 198             "ensureInt", int.class, Object.class, int.class);
 199     private static final Call ENSURE_LONG = CompilerConstants.staticCallNoLookup(OptimisticReturnFilters.class,
 200             "ensureLong", long.class, Object.class, int.class);
 201     private static final Call ENSURE_NUMBER = CompilerConstants.staticCallNoLookup(OptimisticReturnFilters.class,
 202             "ensureNumber", double.class, Object.class, int.class);
 203 
 204     private static final Class<?> ITERATOR_CLASS = Iterator.class;
 205     static {
 206         assert ITERATOR_CLASS == CompilerConstants.ITERATOR_PREFIX.type();
 207     }
 208     private static final Type ITERATOR_TYPE = Type.typeFor(ITERATOR_CLASS);
 209     private static final Type EXCEPTION_TYPE = Type.typeFor(CompilerConstants.EXCEPTION_PREFIX.type());
 210 
 211     private static final Integer INT_ZERO = Integer.valueOf(0);
 212 
 213     /** Constant data & installation. The only reason the compiler keeps this is because it is assigned
 214      *  by reflection in class installation */
 215     private final Compiler compiler;
 216 
 217     /** Is the current code submitted by 'eval' call? */
 218     private final boolean evalCode;
 219 
 220     /** Call site flags given to the code generator to be used for all generated call sites */
 221     private final int callSiteFlags;
 222 
 223     /** How many regexp fields have been emitted */
 224     private int regexFieldCount;
 225 
 226     /** Line number for last statement. If we encounter a new line number, line number bytecode information
 227      *  needs to be generated */
 228     private int lastLineNumber = -1;
 229 
 230     /** When should we stop caching regexp expressions in fields to limit bytecode size? */
 231     private static final int MAX_REGEX_FIELDS = 2 * 1024;
 232 
 233     /** Current method emitter */
 234     private MethodEmitter method;
 235 
 236     /** Current compile unit */
 237     private CompileUnit unit;
 238 
 239     private final DebugLogger log;
 240 
 241     /** From what size should we use spill instead of fields for JavaScript objects? */
 242     private static final int OBJECT_SPILL_THRESHOLD = Options.getIntProperty("nashorn.spill.threshold", 256);
 243 
 244     private final Set<String> emittedMethods = new HashSet<>();
 245 
 246     // Function Id -> ContinuationInfo. Used by compilation of rest-of function only.
 247     private final Map<Integer, ContinuationInfo> fnIdToContinuationInfo = new HashMap<>();
 248 
 249     private final Deque<Label> scopeEntryLabels = new ArrayDeque<>();
 250 
 251     private static final Label METHOD_BOUNDARY = new Label("");
 252     private final Deque<Label> catchLabels = new ArrayDeque<>();
 253     // Number of live locals on entry to (and thus also break from) labeled blocks.
 254     private final IntDeque labeledBlockBreakLiveLocals = new IntDeque();
 255 
 256     //is this a rest of compilation
 257     private final int[] continuationEntryPoints;
 258 
 259     /**
 260      * Constructor.
 261      *
 262      * @param compiler
 263      */
 264     CodeGenerator(final Compiler compiler, final int[] continuationEntryPoints) {
 265         super(new CodeGeneratorLexicalContext());
 266         this.compiler                = compiler;
 267         this.evalCode                = compiler.getSource().isEvalCode();
 268         this.continuationEntryPoints = continuationEntryPoints;
 269         this.callSiteFlags           = compiler.getScriptEnvironment()._callsite_flags;
 270         this.log                     = initLogger(compiler.getContext());
 271     }
 272 
 273     @Override
 274     public DebugLogger getLogger() {
 275         return log;
 276     }
 277 
 278     @Override
 279     public DebugLogger initLogger(final Context context) {
 280         return context.getLogger(this.getClass());
 281     }
 282 
 283     /**
 284      * Gets the call site flags, adding the strict flag if the current function
 285      * being generated is in strict mode
 286      *
 287      * @return the correct flags for a call site in the current function
 288      */
 289     int getCallSiteFlags() {
 290         return lc.getCurrentFunction().getCallSiteFlags() | callSiteFlags;
 291     }
 292 
 293     /**
 294      * Are we generating code for 'eval' code?
 295      * @return true if currently compiled code is 'eval' code.
 296      */
 297     boolean isEvalCode() {
 298         return evalCode;
 299     }
 300 
 301     /**
 302      * Load an identity node
 303      *
 304      * @param identNode an identity node to load
 305      * @return the method generator used
 306      */
 307     private MethodEmitter loadIdent(final IdentNode identNode, final TypeBounds resultBounds) {
 308         checkTemporalDeadZone(identNode);
 309         final Symbol symbol = identNode.getSymbol();
 310 
 311         if (!symbol.isScope()) {
 312             final Type type = identNode.getType();
 313             if(type == Type.UNDEFINED) {
 314                 return method.loadUndefined(resultBounds.widest);
 315             }
 316 
 317             assert symbol.hasSlot() || symbol.isParam();
 318             return method.load(identNode);
 319         }
 320 
 321         assert identNode.getSymbol().isScope() : identNode + " is not in scope!";
 322         final int flags = CALLSITE_SCOPE | getCallSiteFlags();
 323         if (isFastScope(symbol)) {
 324             // Only generate shared scope getter for fast-scope symbols so we know we can dial in correct scope.
 325             if (symbol.getUseCount() > SharedScopeCall.FAST_SCOPE_GET_THRESHOLD && !isOptimisticOrRestOf()) {
 326                 method.loadCompilerConstant(SCOPE);
 327                 // As shared scope vars are only used in non-optimistic compilation, we switch from using TypeBounds to
 328                 // just a single definitive type, resultBounds.widest.
 329                 loadSharedScopeVar(resultBounds.widest, symbol, flags);
 330             } else {
 331                 new LoadFastScopeVar(identNode, resultBounds, flags).emit();
 332             }
 333         } else {
 334             //slow scope load, we have no proto depth
 335             new LoadScopeVar(identNode, resultBounds, flags).emit();
 336         }
 337 
 338         return method;
 339     }
 340 
 341     // Any access to LET and CONST variables before their declaration must throw ReferenceError.
 342     // This is called the temporal dead zone (TDZ). See https://gist.github.com/rwaldron/f0807a758aa03bcdd58a
 343     private void checkTemporalDeadZone(final IdentNode identNode) {
 344         if (identNode.isDead()) {
 345             method.load(identNode.getSymbol().getName());
 346             method.invoke(ScriptRuntime.THROW_REFERENCE_ERROR);
 347         }
 348     }
 349 
 350     private boolean isRestOf() {
 351         return continuationEntryPoints != null;
 352     }
 353 
 354     private boolean isOptimisticOrRestOf() {
 355         return useOptimisticTypes() || isRestOf();
 356     }
 357 
 358     private boolean isCurrentContinuationEntryPoint(final int programPoint) {
 359         return isRestOf() && getCurrentContinuationEntryPoint() == programPoint;
 360     }
 361 
 362     private int[] getContinuationEntryPoints() {
 363         return isRestOf() ? continuationEntryPoints : null;
 364     }
 365 
 366     private int getCurrentContinuationEntryPoint() {
 367         return isRestOf() ? continuationEntryPoints[0] : INVALID_PROGRAM_POINT;
 368     }
 369 
 370     private boolean isContinuationEntryPoint(final int programPoint) {
 371         if (isRestOf()) {
 372             assert continuationEntryPoints != null;
 373             for (final int cep : continuationEntryPoints) {
 374                 if (cep == programPoint) {
 375                     return true;
 376                 }
 377             }
 378         }
 379         return false;
 380     }
 381 
 382     /**
 383      * Check if this symbol can be accessed directly with a putfield or getfield or dynamic load
 384      *
 385      * @param symbol symbol to check for fast scope
 386      * @return true if fast scope
 387      */
 388     private boolean isFastScope(final Symbol symbol) {
 389         if (!symbol.isScope()) {
 390             return false;
 391         }
 392 
 393         if (!lc.inDynamicScope()) {
 394             // If there's no with or eval in context, and the symbol is marked as scoped, it is fast scoped. Such a
 395             // symbol must either be global, or its defining block must need scope.
 396             assert symbol.isGlobal() || lc.getDefiningBlock(symbol).needsScope() : symbol.getName();
 397             return true;
 398         }
 399 
 400         if (symbol.isGlobal()) {
 401             // Shortcut: if there's a with or eval in context, globals can't be fast scoped
 402             return false;
 403         }
 404 
 405         // Otherwise, check if there's a dynamic scope between use of the symbol and its definition
 406         final String name = symbol.getName();
 407         boolean previousWasBlock = false;
 408         for (final Iterator<LexicalContextNode> it = lc.getAllNodes(); it.hasNext();) {
 409             final LexicalContextNode node = it.next();
 410             if (node instanceof Block) {
 411                 // If this block defines the symbol, then we can fast scope the symbol.
 412                 final Block block = (Block)node;
 413                 if (block.getExistingSymbol(name) == symbol) {
 414                     assert block.needsScope();
 415                     return true;
 416                 }
 417                 previousWasBlock = true;
 418             } else {
 419                 if (node instanceof WithNode && previousWasBlock || node instanceof FunctionNode && ((FunctionNode)node).needsDynamicScope()) {
 420                     // If we hit a scope that can have symbols introduced into it at run time before finding the defining
 421                     // block, the symbol can't be fast scoped. A WithNode only counts if we've immediately seen a block
 422                     // before - its block. Otherwise, we are currently processing the WithNode's expression, and that's
 423                     // obviously not subjected to introducing new symbols.
 424                     return false;
 425                 }
 426                 previousWasBlock = false;
 427             }
 428         }
 429         // Should've found the symbol defined in a block
 430         throw new AssertionError();
 431     }
 432 
 433     private MethodEmitter loadSharedScopeVar(final Type valueType, final Symbol symbol, final int flags) {
 434         assert !isOptimisticOrRestOf();
 435         if (isFastScope(symbol)) {
 436             method.load(getScopeProtoDepth(lc.getCurrentBlock(), symbol));
 437         } else {
 438             method.load(-1);
 439         }
 440         return lc.getScopeGet(unit, symbol, valueType, flags | CALLSITE_FAST_SCOPE).generateInvoke(method);
 441     }
 442 
 443     private class LoadScopeVar extends OptimisticOperation {
 444         final IdentNode identNode;
 445         private final int flags;
 446 
 447         LoadScopeVar(final IdentNode identNode, final TypeBounds resultBounds, final int flags) {
 448             super(identNode, resultBounds);
 449             this.identNode = identNode;
 450             this.flags = flags;
 451         }
 452 
 453         @Override
 454         void loadStack() {
 455             method.loadCompilerConstant(SCOPE);
 456             getProto();
 457         }
 458 
 459         void getProto() {
 460             //empty
 461         }
 462 
 463         @Override
 464         void consumeStack() {
 465             // If this is either __FILE__, __DIR__, or __LINE__ then load the property initially as Object as we'd convert
 466             // it anyway for replaceLocationPropertyPlaceholder.
 467             if(identNode.isCompileTimePropertyName()) {
 468                 method.dynamicGet(Type.OBJECT, identNode.getSymbol().getName(), flags, identNode.isFunction(), false);
 469                 replaceCompileTimeProperty();
 470             } else {
 471                 dynamicGet(identNode.getSymbol().getName(), flags, identNode.isFunction(), false);
 472             }
 473         }
 474     }
 475 
 476     private class LoadFastScopeVar extends LoadScopeVar {
 477         LoadFastScopeVar(final IdentNode identNode, final TypeBounds resultBounds, final int flags) {
 478             super(identNode, resultBounds, flags | CALLSITE_FAST_SCOPE);
 479         }
 480 
 481         @Override
 482         void getProto() {
 483             loadFastScopeProto(identNode.getSymbol(), false);
 484         }
 485     }
 486 
 487     private MethodEmitter storeFastScopeVar(final Symbol symbol, final int flags) {
 488         loadFastScopeProto(symbol, true);
 489         method.dynamicSet(symbol.getName(), flags | CALLSITE_FAST_SCOPE, false);
 490         return method;
 491     }
 492 
 493     private int getScopeProtoDepth(final Block startingBlock, final Symbol symbol) {
 494         //walk up the chain from starting block and when we bump into the current function boundary, add the external
 495         //information.
 496         final FunctionNode fn   = lc.getCurrentFunction();
 497         final int externalDepth = compiler.getScriptFunctionData(fn.getId()).getExternalSymbolDepth(symbol.getName());
 498 
 499         //count the number of scopes from this place to the start of the function
 500 
 501         final int internalDepth = FindScopeDepths.findInternalDepth(lc, fn, startingBlock, symbol);
 502         final int scopesToStart = FindScopeDepths.findScopesToStart(lc, fn, startingBlock);
 503         int depth = 0;
 504         if (internalDepth == -1) {
 505             depth = scopesToStart + externalDepth;
 506         } else {
 507             assert internalDepth <= scopesToStart;
 508             depth = internalDepth;
 509         }
 510 
 511         return depth;
 512     }
 513 
 514     private void loadFastScopeProto(final Symbol symbol, final boolean swap) {
 515         final int depth = getScopeProtoDepth(lc.getCurrentBlock(), symbol);
 516         assert depth != -1 : "Couldn't find scope depth for symbol " + symbol.getName() + " in " + lc.getCurrentFunction();
 517         if (depth > 0) {
 518             if (swap) {
 519                 method.swap();
 520             }
 521             for (int i = 0; i < depth; i++) {
 522                 method.invoke(ScriptObject.GET_PROTO);
 523             }
 524             if (swap) {
 525                 method.swap();
 526             }
 527         }
 528     }
 529 
 530     /**
 531      * Generate code that loads this node to the stack, not constraining its type
 532      *
 533      * @param expr node to load
 534      *
 535      * @return the method emitter used
 536      */
 537     private MethodEmitter loadExpressionUnbounded(final Expression expr) {
 538         return loadExpression(expr, TypeBounds.UNBOUNDED);
 539     }
 540 
 541     private MethodEmitter loadExpressionAsObject(final Expression expr) {
 542         return loadExpression(expr, TypeBounds.OBJECT);
 543     }
 544 
 545     MethodEmitter loadExpressionAsBoolean(final Expression expr) {
 546         return loadExpression(expr, TypeBounds.BOOLEAN);
 547     }
 548 
 549     // Test whether conversion from source to target involves a call of ES 9.1 ToPrimitive
 550     // with possible side effects from calling an object's toString or valueOf methods.
 551     private static boolean noToPrimitiveConversion(final Type source, final Type target) {
 552         // Object to boolean conversion does not cause ToPrimitive call
 553         return source.isJSPrimitive() || !target.isJSPrimitive() || target.isBoolean();
 554     }
 555 
 556     MethodEmitter loadBinaryOperands(final BinaryNode binaryNode) {
 557         return loadBinaryOperands(binaryNode.lhs(), binaryNode.rhs(), TypeBounds.UNBOUNDED.notWiderThan(binaryNode.getWidestOperandType()), false, false);
 558     }
 559 
 560     private MethodEmitter loadBinaryOperands(final Expression lhs, final Expression rhs, final TypeBounds explicitOperandBounds, final boolean baseAlreadyOnStack, final boolean forceConversionSeparation) {
 561         // ECMAScript 5.1 specification (sections 11.5-11.11 and 11.13) prescribes that when evaluating a binary
 562         // expression "LEFT op RIGHT", the order of operations must be: LOAD LEFT, LOAD RIGHT, CONVERT LEFT, CONVERT
 563         // RIGHT, EXECUTE OP. Unfortunately, doing it in this order defeats potential optimizations that arise when we
 564         // can combine a LOAD with a CONVERT operation (e.g. use a dynamic getter with the conversion target type as its
 565         // return value). What we do here is reorder LOAD RIGHT and CONVERT LEFT when possible; it is possible only when
 566         // we can prove that executing CONVERT LEFT can't have a side effect that changes the value of LOAD RIGHT.
 567         // Basically, if we know that either LEFT already is a primitive value, or does not have to be converted to
 568         // a primitive value, or RIGHT is an expression that loads without side effects, then we can do the
 569         // reordering and collapse LOAD/CONVERT into a single operation; otherwise we need to do the more costly
 570         // separate operations to preserve specification semantics.
 571 
 572         // Operands' load type should not be narrower than the narrowest of the individual operand types, nor narrower
 573         // than the lower explicit bound, but it should also not be wider than
 574         final Type lhsType = undefinedToNumber(lhs.getType());
 575         final Type rhsType = undefinedToNumber(rhs.getType());
 576         final Type narrowestOperandType = Type.narrowest(Type.widest(lhsType, rhsType), explicitOperandBounds.widest);
 577         final TypeBounds operandBounds = explicitOperandBounds.notNarrowerThan(narrowestOperandType);
 578         if (noToPrimitiveConversion(lhsType, explicitOperandBounds.widest) || rhs.isLocal()) {
 579             // Can reorder. We might still need to separate conversion, but at least we can do it with reordering
 580             if (forceConversionSeparation) {
 581                 // Can reorder, but can't move conversion into the operand as the operation depends on operands
 582                 // exact types for its overflow guarantees. E.g. with {L}{%I}expr1 {L}* {L}{%I}expr2 we are not allowed
 583                 // to merge {L}{%I} into {%L}, as that can cause subsequent overflows; test for JDK-8058610 contains
 584                 // concrete cases where this could happen.
 585                 final TypeBounds safeConvertBounds = TypeBounds.UNBOUNDED.notNarrowerThan(narrowestOperandType);
 586                 loadExpression(lhs, safeConvertBounds, baseAlreadyOnStack);
 587                 method.convert(operandBounds.within(method.peekType()));
 588                 loadExpression(rhs, safeConvertBounds, false);
 589                 method.convert(operandBounds.within(method.peekType()));
 590             } else {
 591                 // Can reorder and move conversion into the operand. Combine load and convert into single operations.
 592                 loadExpression(lhs, operandBounds, baseAlreadyOnStack);
 593                 loadExpression(rhs, operandBounds, false);
 594             }
 595         } else {
 596             // Can't reorder. Load and convert separately.
 597             final TypeBounds safeConvertBounds = TypeBounds.UNBOUNDED.notNarrowerThan(narrowestOperandType);
 598             loadExpression(lhs, safeConvertBounds, baseAlreadyOnStack);
 599             final Type lhsLoadedType = method.peekType();
 600             loadExpression(rhs, safeConvertBounds, false);
 601             final Type convertedLhsType = operandBounds.within(method.peekType());
 602             if (convertedLhsType != lhsLoadedType) {
 603                 // Do it conditionally, so that if conversion is a no-op we don't introduce a SWAP, SWAP.
 604                 method.swap().convert(convertedLhsType).swap();
 605             }
 606             method.convert(operandBounds.within(method.peekType()));
 607         }
 608         assert Type.generic(method.peekType()) == operandBounds.narrowest;
 609         assert Type.generic(method.peekType(1)) == operandBounds.narrowest;
 610 
 611         return method;
 612     }
 613 
 614     private static final Type undefinedToNumber(final Type type) {
 615         return type == Type.UNDEFINED ? Type.NUMBER : type;
 616     }
 617 
 618     private static final class TypeBounds {
 619         final Type narrowest;
 620         final Type widest;
 621 
 622         static final TypeBounds UNBOUNDED = new TypeBounds(Type.UNKNOWN, Type.OBJECT);
 623         static final TypeBounds INT = exact(Type.INT);
 624         static final TypeBounds OBJECT = exact(Type.OBJECT);
 625         static final TypeBounds BOOLEAN = exact(Type.BOOLEAN);
 626 
 627         static TypeBounds exact(final Type type) {
 628             return new TypeBounds(type, type);
 629         }
 630 
 631         TypeBounds(final Type narrowest, final Type widest) {
 632             assert widest    != null && widest    != Type.UNDEFINED && widest != Type.UNKNOWN : widest;
 633             assert narrowest != null && narrowest != Type.UNDEFINED : narrowest;
 634             assert !narrowest.widerThan(widest) : narrowest + " wider than " + widest;
 635             assert !widest.narrowerThan(narrowest);
 636             this.narrowest = Type.generic(narrowest);
 637             this.widest = Type.generic(widest);
 638         }
 639 
 640         TypeBounds notNarrowerThan(final Type type) {
 641             return maybeNew(Type.narrowest(Type.widest(narrowest, type), widest), widest);
 642         }
 643 
 644         TypeBounds notWiderThan(final Type type) {
 645             return maybeNew(Type.narrowest(narrowest, type), Type.narrowest(widest, type));
 646         }
 647 
 648         boolean canBeNarrowerThan(final Type type) {
 649             return narrowest.narrowerThan(type);
 650         }
 651 
 652         TypeBounds maybeNew(final Type newNarrowest, final Type newWidest) {
 653             if(newNarrowest == narrowest && newWidest == widest) {
 654                 return this;
 655             }
 656             return new TypeBounds(newNarrowest, newWidest);
 657         }
 658 
 659         TypeBounds booleanToInt() {
 660             return maybeNew(CodeGenerator.booleanToInt(narrowest), CodeGenerator.booleanToInt(widest));
 661         }
 662 
 663         TypeBounds objectToNumber() {
 664             return maybeNew(CodeGenerator.objectToNumber(narrowest), CodeGenerator.objectToNumber(widest));
 665         }
 666 
 667         Type within(final Type type) {
 668             if(type.narrowerThan(narrowest)) {
 669                 return narrowest;
 670             }
 671             if(type.widerThan(widest)) {
 672                 return widest;
 673             }
 674             return type;
 675         }
 676 
 677         @Override
 678         public String toString() {
 679             return "[" + narrowest + ", " + widest + "]";
 680         }
 681     }
 682 
 683     private static Type booleanToInt(final Type t) {
 684         return t == Type.BOOLEAN ? Type.INT : t;
 685     }
 686 
 687     private static Type objectToNumber(final Type t) {
 688         return t.isObject() ? Type.NUMBER : t;
 689     }
 690 
 691     MethodEmitter loadExpressionAsType(final Expression expr, final Type type) {
 692         if(type == Type.BOOLEAN) {
 693             return loadExpressionAsBoolean(expr);
 694         } else if(type == Type.UNDEFINED) {
 695             assert expr.getType() == Type.UNDEFINED;
 696             return loadExpressionAsObject(expr);
 697         }
 698         // having no upper bound preserves semantics of optimistic operations in the expression (by not having them
 699         // converted early) and then applies explicit conversion afterwards.
 700         return loadExpression(expr, TypeBounds.UNBOUNDED.notNarrowerThan(type)).convert(type);
 701     }
 702 
 703     private MethodEmitter loadExpression(final Expression expr, final TypeBounds resultBounds) {
 704         return loadExpression(expr, resultBounds, false);
 705     }
 706 
 707     /**
 708      * Emits code for evaluating an expression and leaving its value on top of the stack, narrowing or widening it if
 709      * necessary.
 710      * @param expr the expression to load
 711      * @param resultBounds the incoming type bounds. The value on the top of the stack is guaranteed to not be of narrower
 712      * type than the narrowest bound, or wider type than the widest bound after it is loaded.
 713      * @param baseAlreadyOnStack true if the base of an access or index node is already on the stack. Used to avoid
 714      * double evaluation of bases in self-assignment expressions to access and index nodes. {@code Type.OBJECT} is used
 715      * to indicate the widest possible type.
 716      * @return the method emitter
 717      */
 718     private MethodEmitter loadExpression(final Expression expr, final TypeBounds resultBounds, final boolean baseAlreadyOnStack) {
 719 
 720         /*
 721          * The load may be of type IdentNode, e.g. "x", AccessNode, e.g. "x.y"
 722          * or IndexNode e.g. "x[y]". Both AccessNodes and IndexNodes are
 723          * BaseNodes and the logic for loading the base object is reused
 724          */
 725         final CodeGenerator codegen = this;
 726 
 727         final Node currentDiscard = codegen.lc.getCurrentDiscard();
 728         expr.accept(new NodeOperatorVisitor<LexicalContext>(new LexicalContext()) {
 729             @Override
 730             public boolean enterIdentNode(final IdentNode identNode) {
 731                 loadIdent(identNode, resultBounds);
 732                 return false;
 733             }
 734 
 735             @Override
 736             public boolean enterAccessNode(final AccessNode accessNode) {
 737                 new OptimisticOperation(accessNode, resultBounds) {
 738                     @Override
 739                     void loadStack() {
 740                         if (!baseAlreadyOnStack) {
 741                             loadExpressionAsObject(accessNode.getBase());
 742                         }
 743                         assert method.peekType().isObject();
 744                     }
 745                     @Override
 746                     void consumeStack() {
 747                         final int flags = getCallSiteFlags();
 748                         dynamicGet(accessNode.getProperty(), flags, accessNode.isFunction(), accessNode.isIndex());
 749                     }
 750                 }.emit(baseAlreadyOnStack ? 1 : 0);
 751                 return false;
 752             }
 753 
 754             @Override
 755             public boolean enterIndexNode(final IndexNode indexNode) {
 756                 new OptimisticOperation(indexNode, resultBounds) {
 757                     @Override
 758                     void loadStack() {
 759                         if (!baseAlreadyOnStack) {
 760                             loadExpressionAsObject(indexNode.getBase());
 761                             loadExpressionUnbounded(indexNode.getIndex());
 762                         }
 763                     }
 764                     @Override
 765                     void consumeStack() {
 766                         final int flags = getCallSiteFlags();
 767                         dynamicGetIndex(flags, indexNode.isFunction());
 768                     }
 769                 }.emit(baseAlreadyOnStack ? 2 : 0);
 770                 return false;
 771             }
 772 
 773             @Override
 774             public boolean enterFunctionNode(final FunctionNode functionNode) {
 775                 // function nodes will always leave a constructed function object on stack, no need to load the symbol
 776                 // separately as in enterDefault()
 777                 lc.pop(functionNode);
 778                 functionNode.accept(codegen);
 779                 // NOTE: functionNode.accept() will produce a different FunctionNode that we discard. This incidentally
 780                 // doesn't cause problems as we're never touching FunctionNode again after it's visited here - codegen
 781                 // is the last element in the compilation pipeline, the AST it produces is not used externally. So, we
 782                 // re-push the original functionNode.
 783                 lc.push(functionNode);
 784                 return false;
 785             }
 786 
 787             @Override
 788             public boolean enterASSIGN(final BinaryNode binaryNode) {
 789                 loadASSIGN(binaryNode);
 790                 return false;
 791             }
 792 
 793             @Override
 794             public boolean enterASSIGN_ADD(final BinaryNode binaryNode) {
 795                 loadASSIGN_ADD(binaryNode);
 796                 return false;
 797             }
 798 
 799             @Override
 800             public boolean enterASSIGN_BIT_AND(final BinaryNode binaryNode) {
 801                 loadASSIGN_BIT_AND(binaryNode);
 802                 return false;
 803             }
 804 
 805             @Override
 806             public boolean enterASSIGN_BIT_OR(final BinaryNode binaryNode) {
 807                 loadASSIGN_BIT_OR(binaryNode);
 808                 return false;
 809             }
 810 
 811             @Override
 812             public boolean enterASSIGN_BIT_XOR(final BinaryNode binaryNode) {
 813                 loadASSIGN_BIT_XOR(binaryNode);
 814                 return false;
 815             }
 816 
 817             @Override
 818             public boolean enterASSIGN_DIV(final BinaryNode binaryNode) {
 819                 loadASSIGN_DIV(binaryNode);
 820                 return false;
 821             }
 822 
 823             @Override
 824             public boolean enterASSIGN_MOD(final BinaryNode binaryNode) {
 825                 loadASSIGN_MOD(binaryNode);
 826                 return false;
 827             }
 828 
 829             @Override
 830             public boolean enterASSIGN_MUL(final BinaryNode binaryNode) {
 831                 loadASSIGN_MUL(binaryNode);
 832                 return false;
 833             }
 834 
 835             @Override
 836             public boolean enterASSIGN_SAR(final BinaryNode binaryNode) {
 837                 loadASSIGN_SAR(binaryNode);
 838                 return false;
 839             }
 840 
 841             @Override
 842             public boolean enterASSIGN_SHL(final BinaryNode binaryNode) {
 843                 loadASSIGN_SHL(binaryNode);
 844                 return false;
 845             }
 846 
 847             @Override
 848             public boolean enterASSIGN_SHR(final BinaryNode binaryNode) {
 849                 loadASSIGN_SHR(binaryNode);
 850                 return false;
 851             }
 852 
 853             @Override
 854             public boolean enterASSIGN_SUB(final BinaryNode binaryNode) {
 855                 loadASSIGN_SUB(binaryNode);
 856                 return false;
 857             }
 858 
 859             @Override
 860             public boolean enterCallNode(final CallNode callNode) {
 861                 return loadCallNode(callNode, resultBounds);
 862             }
 863 
 864             @Override
 865             public boolean enterLiteralNode(final LiteralNode<?> literalNode) {
 866                 loadLiteral(literalNode, resultBounds);
 867                 return false;
 868             }
 869 
 870             @Override
 871             public boolean enterTernaryNode(final TernaryNode ternaryNode) {
 872                 loadTernaryNode(ternaryNode, resultBounds);
 873                 return false;
 874             }
 875 
 876             @Override
 877             public boolean enterADD(final BinaryNode binaryNode) {
 878                 loadADD(binaryNode, resultBounds);
 879                 return false;
 880             }
 881 
 882             @Override
 883             public boolean enterSUB(final UnaryNode unaryNode) {
 884                 loadSUB(unaryNode, resultBounds);
 885                 return false;
 886             }
 887 
 888             @Override
 889             public boolean enterSUB(final BinaryNode binaryNode) {
 890                 loadSUB(binaryNode, resultBounds);
 891                 return false;
 892             }
 893 
 894             @Override
 895             public boolean enterMUL(final BinaryNode binaryNode) {
 896                 loadMUL(binaryNode, resultBounds);
 897                 return false;
 898             }
 899 
 900             @Override
 901             public boolean enterDIV(final BinaryNode binaryNode) {
 902                 loadDIV(binaryNode, resultBounds);
 903                 return false;
 904             }
 905 
 906             @Override
 907             public boolean enterMOD(final BinaryNode binaryNode) {
 908                 loadMOD(binaryNode, resultBounds);
 909                 return false;
 910             }
 911 
 912             @Override
 913             public boolean enterSAR(final BinaryNode binaryNode) {
 914                 loadSAR(binaryNode);
 915                 return false;
 916             }
 917 
 918             @Override
 919             public boolean enterSHL(final BinaryNode binaryNode) {
 920                 loadSHL(binaryNode);
 921                 return false;
 922             }
 923 
 924             @Override
 925             public boolean enterSHR(final BinaryNode binaryNode) {
 926                 loadSHR(binaryNode);
 927                 return false;
 928             }
 929 
 930             @Override
 931             public boolean enterCOMMALEFT(final BinaryNode binaryNode) {
 932                 loadCOMMALEFT(binaryNode, resultBounds);
 933                 return false;
 934             }
 935 
 936             @Override
 937             public boolean enterCOMMARIGHT(final BinaryNode binaryNode) {
 938                 loadCOMMARIGHT(binaryNode, resultBounds);
 939                 return false;
 940             }
 941 
 942             @Override
 943             public boolean enterAND(final BinaryNode binaryNode) {
 944                 loadAND_OR(binaryNode, resultBounds, true);
 945                 return false;
 946             }
 947 
 948             @Override
 949             public boolean enterOR(final BinaryNode binaryNode) {
 950                 loadAND_OR(binaryNode, resultBounds, false);
 951                 return false;
 952             }
 953 
 954             @Override
 955             public boolean enterNOT(final UnaryNode unaryNode) {
 956                 loadNOT(unaryNode);
 957                 return false;
 958             }
 959 
 960             @Override
 961             public boolean enterADD(final UnaryNode unaryNode) {
 962                 loadADD(unaryNode, resultBounds);
 963                 return false;
 964             }
 965 
 966             @Override
 967             public boolean enterBIT_NOT(final UnaryNode unaryNode) {
 968                 loadBIT_NOT(unaryNode);
 969                 return false;
 970             }
 971 
 972             @Override
 973             public boolean enterBIT_AND(final BinaryNode binaryNode) {
 974                 loadBIT_AND(binaryNode);
 975                 return false;
 976             }
 977 
 978             @Override
 979             public boolean enterBIT_OR(final BinaryNode binaryNode) {
 980                 loadBIT_OR(binaryNode);
 981                 return false;
 982             }
 983 
 984             @Override
 985             public boolean enterBIT_XOR(final BinaryNode binaryNode) {
 986                 loadBIT_XOR(binaryNode);
 987                 return false;
 988             }
 989 
 990             @Override
 991             public boolean enterVOID(final UnaryNode unaryNode) {
 992                 loadVOID(unaryNode, resultBounds);
 993                 return false;
 994             }
 995 
 996             @Override
 997             public boolean enterEQ(final BinaryNode binaryNode) {
 998                 loadCmp(binaryNode, Condition.EQ);
 999                 return false;
1000             }
1001 
1002             @Override
1003             public boolean enterEQ_STRICT(final BinaryNode binaryNode) {
1004                 loadCmp(binaryNode, Condition.EQ);
1005                 return false;
1006             }
1007 
1008             @Override
1009             public boolean enterGE(final BinaryNode binaryNode) {
1010                 loadCmp(binaryNode, Condition.GE);
1011                 return false;
1012             }
1013 
1014             @Override
1015             public boolean enterGT(final BinaryNode binaryNode) {
1016                 loadCmp(binaryNode, Condition.GT);
1017                 return false;
1018             }
1019 
1020             @Override
1021             public boolean enterLE(final BinaryNode binaryNode) {
1022                 loadCmp(binaryNode, Condition.LE);
1023                 return false;
1024             }
1025 
1026             @Override
1027             public boolean enterLT(final BinaryNode binaryNode) {
1028                 loadCmp(binaryNode, Condition.LT);
1029                 return false;
1030             }
1031 
1032             @Override
1033             public boolean enterNE(final BinaryNode binaryNode) {
1034                 loadCmp(binaryNode, Condition.NE);
1035                 return false;
1036             }
1037 
1038             @Override
1039             public boolean enterNE_STRICT(final BinaryNode binaryNode) {
1040                 loadCmp(binaryNode, Condition.NE);
1041                 return false;
1042             }
1043 
1044             @Override
1045             public boolean enterObjectNode(final ObjectNode objectNode) {
1046                 loadObjectNode(objectNode);
1047                 return false;
1048             }
1049 
1050             @Override
1051             public boolean enterRuntimeNode(final RuntimeNode runtimeNode) {
1052                 loadRuntimeNode(runtimeNode);
1053                 return false;
1054             }
1055 
1056             @Override
1057             public boolean enterNEW(final UnaryNode unaryNode) {
1058                 loadNEW(unaryNode);
1059                 return false;
1060             }
1061 
1062             @Override
1063             public boolean enterDECINC(final UnaryNode unaryNode) {
1064                 loadDECINC(unaryNode);
1065                 return false;
1066             }
1067 
1068             @Override
1069             public boolean enterJoinPredecessorExpression(final JoinPredecessorExpression joinExpr) {
1070                 loadExpression(joinExpr.getExpression(), resultBounds);
1071                 return false;
1072             }
1073 
1074             @Override
1075             public boolean enterGetSplitState(final GetSplitState getSplitState) {
1076                 method.loadScope();
1077                 method.invoke(Scope.GET_SPLIT_STATE);
1078                 return false;
1079             }
1080 
1081             @Override
1082             public boolean enterDefault(final Node otherNode) {
1083                 // Must have handled all expressions that can legally be encountered.
1084                 throw new AssertionError(otherNode.getClass().getName());
1085             }
1086         });
1087         if(currentDiscard != expr) {
1088             coerceStackTop(resultBounds);
1089         }
1090         return method;
1091     }
1092 
1093     private MethodEmitter coerceStackTop(final TypeBounds typeBounds) {
1094         return method.convert(typeBounds.within(method.peekType()));
1095     }
1096 
1097     /**
1098      * Closes any still open entries for this block's local variables in the bytecode local variable table.
1099      *
1100      * @param block block containing symbols.
1101      */
1102     private void closeBlockVariables(final Block block) {
1103         for (final Symbol symbol : block.getSymbols()) {
1104             if (symbol.isBytecodeLocal()) {
1105                 method.closeLocalVariable(symbol, block.getBreakLabel());
1106             }
1107         }
1108     }
1109 
1110     @Override
1111     public boolean enterBlock(final Block block) {
1112         method.label(block.getEntryLabel());
1113         if(!method.isReachable()) {
1114             return false;
1115         }
1116         if(lc.isFunctionBody() && emittedMethods.contains(lc.getCurrentFunction().getName())) {
1117             return false;
1118         }
1119         initLocals(block);
1120 
1121         assert lc.getUsedSlotCount() == method.getFirstTemp();
1122         return true;
1123     }
1124 
1125     private boolean useOptimisticTypes() {
1126         return !lc.inSplitNode() && compiler.useOptimisticTypes();
1127     }
1128 
1129     @Override
1130     public Node leaveBlock(final Block block) {
1131         popBlockScope(block);
1132         method.beforeJoinPoint(block);
1133 
1134         closeBlockVariables(block);
1135         lc.releaseSlots();
1136         assert !method.isReachable() || (lc.isFunctionBody() ? 0 : lc.getUsedSlotCount()) == method.getFirstTemp() :
1137             "reachable="+method.isReachable() +
1138             " isFunctionBody=" + lc.isFunctionBody() +
1139             " usedSlotCount=" + lc.getUsedSlotCount() +
1140             " firstTemp=" + method.getFirstTemp();
1141 
1142         return block;
1143     }
1144 
1145     private void popBlockScope(final Block block) {
1146         final Label breakLabel = block.getBreakLabel();
1147 
1148         if(!block.needsScope() || lc.isFunctionBody()) {
1149             emitBlockBreakLabel(breakLabel);
1150             return;
1151         }
1152 
1153         final Label beginTryLabel = scopeEntryLabels.pop();
1154         final Label recoveryLabel = new Label("block_popscope_catch");
1155         emitBlockBreakLabel(breakLabel);
1156         final boolean bodyCanThrow = breakLabel.isAfter(beginTryLabel);
1157         if(bodyCanThrow) {
1158             method._try(beginTryLabel, breakLabel, recoveryLabel);
1159         }
1160 
1161         Label afterCatchLabel = null;
1162 
1163         if(method.isReachable()) {
1164             popScope();
1165             if(bodyCanThrow) {
1166                 afterCatchLabel = new Label("block_after_catch");
1167                 method._goto(afterCatchLabel);
1168             }
1169         }
1170 
1171         if(bodyCanThrow) {
1172             assert !method.isReachable();
1173             method._catch(recoveryLabel);
1174             popScopeException();
1175             method.athrow();
1176         }
1177         if(afterCatchLabel != null) {
1178             method.label(afterCatchLabel);
1179         }
1180     }
1181 
1182     private void emitBlockBreakLabel(final Label breakLabel) {
1183         // TODO: this is totally backwards. Block should not be breakable, LabelNode should be breakable.
1184         final LabelNode labelNode = lc.getCurrentBlockLabelNode();
1185         if(labelNode != null) {
1186             // Only have conversions if we're reachable
1187             assert labelNode.getLocalVariableConversion() == null || method.isReachable();
1188             method.beforeJoinPoint(labelNode);
1189             method.breakLabel(breakLabel, labeledBlockBreakLiveLocals.pop());
1190         } else {
1191             method.label(breakLabel);
1192         }
1193     }
1194 
1195     private void popScope() {
1196         popScopes(1);
1197     }
1198 
1199     /**
1200      * Pop scope as part of an exception handler. Similar to {@code popScope()} but also takes care of adjusting the
1201      * number of scopes that needs to be popped in case a rest-of continuation handler encounters an exception while
1202      * performing a ToPrimitive conversion.
1203      */
1204     private void popScopeException() {
1205         popScope();
1206         final ContinuationInfo ci = getContinuationInfo();
1207         if(ci != null) {
1208             final Label catchLabel = ci.catchLabel;
1209             if(catchLabel != METHOD_BOUNDARY && catchLabel == catchLabels.peek()) {
1210                 ++ci.exceptionScopePops;
1211             }
1212         }
1213     }
1214 
1215     private void popScopesUntil(final LexicalContextNode until) {
1216         popScopes(lc.getScopeNestingLevelTo(until));
1217     }
1218 
1219     private void popScopes(final int count) {
1220         if(count == 0) {
1221             return;
1222         }
1223         assert count > 0; // together with count == 0 check, asserts nonnegative count
1224         if (!method.hasScope()) {
1225             // We can sometimes invoke this method even if the method has no slot for the scope object. Typical example:
1226             // for(;;) { with({}) { break; } }. WithNode normally creates a scope, but if it uses no identifiers and
1227             // nothing else forces creation of a scope in the method, we just won't have the :scope local variable.
1228             return;
1229         }
1230         method.loadCompilerConstant(SCOPE);
1231         for(int i = 0; i < count; ++i) {
1232             method.invoke(ScriptObject.GET_PROTO);
1233         }
1234         method.storeCompilerConstant(SCOPE);
1235     }
1236 
1237     @Override
1238     public boolean enterBreakNode(final BreakNode breakNode) {
1239         return enterJumpStatement(breakNode);
1240     }
1241 
1242     private boolean enterJumpStatement(final JumpStatement jump) {
1243         if(!method.isReachable()) {
1244             return false;
1245         }
1246         enterStatement(jump);
1247 
1248         method.beforeJoinPoint(jump);
1249         final BreakableNode target = jump.getTarget(lc);
1250         popScopesUntil(target);
1251         final Label targetLabel = jump.getTargetLabel(target);
1252         targetLabel.markAsBreakTarget();
1253         method._goto(targetLabel);
1254 
1255         return false;
1256     }
1257 
1258     private int loadArgs(final List<Expression> args) {
1259         final int argCount = args.size();
1260         // arg have already been converted to objects here.
1261         if (argCount > LinkerCallSite.ARGLIMIT) {
1262             loadArgsArray(args);
1263             return 1;
1264         }
1265 
1266         for (final Expression arg : args) {
1267             assert arg != null;
1268             loadExpressionUnbounded(arg);
1269         }
1270         return argCount;
1271     }
1272 
1273     private boolean loadCallNode(final CallNode callNode, final TypeBounds resultBounds) {
1274         lineNumber(callNode.getLineNumber());
1275 
1276         final List<Expression> args = callNode.getArgs();
1277         final Expression function = callNode.getFunction();
1278         final Block currentBlock = lc.getCurrentBlock();
1279         final CodeGeneratorLexicalContext codegenLexicalContext = lc;
1280 
1281         function.accept(new NodeVisitor<LexicalContext>(new LexicalContext()) {
1282 
1283             private MethodEmitter sharedScopeCall(final IdentNode identNode, final int flags) {
1284                 final Symbol symbol = identNode.getSymbol();
1285                 final boolean isFastScope = isFastScope(symbol);
1286                 final int scopeCallFlags = flags | (isFastScope ? CALLSITE_FAST_SCOPE : 0);
1287                 new OptimisticOperation(callNode, resultBounds) {
1288                     @Override
1289                     void loadStack() {
1290                         method.loadCompilerConstant(SCOPE);
1291                         if (isFastScope) {
1292                             method.load(getScopeProtoDepth(currentBlock, symbol));
1293                         } else {
1294                             method.load(-1); // Bypass fast-scope code in shared callsite
1295                         }
1296                         loadArgs(args);
1297                     }
1298                     @Override
1299                     void consumeStack() {
1300                         final Type[] paramTypes = method.getTypesFromStack(args.size());
1301                         // We have trouble finding e.g. in Type.typeFor(asm.Type) because it can't see the Context class
1302                         // loader, so we need to weaken reference signatures to Object.
1303                         for(int i = 0; i < paramTypes.length; ++i) {
1304                             paramTypes[i] = Type.generic(paramTypes[i]);
1305                         }
1306                         // As shared scope calls are only used in non-optimistic compilation, we switch from using
1307                         // TypeBounds to just a single definitive type, resultBounds.widest.
1308                         final SharedScopeCall scopeCall = codegenLexicalContext.getScopeCall(unit, symbol,
1309                                 identNode.getType(), resultBounds.widest, paramTypes, scopeCallFlags);
1310                         scopeCall.generateInvoke(method);
1311                     }
1312                 }.emit();
1313                 return method;
1314             }
1315 
1316             private void scopeCall(final IdentNode ident, final int flags) {
1317                 new OptimisticOperation(callNode, resultBounds) {
1318                     int argsCount;
1319                     @Override
1320                     void loadStack() {
1321                         loadExpressionAsObject(ident); // foo() makes no sense if foo == 3
1322                         // ScriptFunction will see CALLSITE_SCOPE and will bind scope accordingly.
1323                         method.loadUndefined(Type.OBJECT); //the 'this'
1324                         argsCount = loadArgs(args);
1325                     }
1326                     @Override
1327                     void consumeStack() {
1328                         dynamicCall(2 + argsCount, flags);
1329                     }
1330                 }.emit();
1331             }
1332 
1333             private void evalCall(final IdentNode ident, final int flags) {
1334                 final Label invoke_direct_eval  = new Label("invoke_direct_eval");
1335                 final Label is_not_eval  = new Label("is_not_eval");
1336                 final Label eval_done = new Label("eval_done");
1337 
1338                 new OptimisticOperation(callNode, resultBounds) {
1339                     int argsCount;
1340                     @Override
1341                     void loadStack() {
1342                         /**
1343                          * We want to load 'eval' to check if it is indeed global builtin eval.
1344                          * If this eval call is inside a 'with' statement, dyn:getMethod|getProp|getElem
1345                          * would be generated if ident is a "isFunction". But, that would result in a
1346                          * bound function from WithObject. We don't want that as bound function as that
1347                          * won't be detected as builtin eval. So, we make ident as "not a function" which
1348                          * results in "dyn:getProp|getElem|getMethod" being generated and so WithObject
1349                          * would return unbounded eval function.
1350                          *
1351                          * Example:
1352                          *
1353                          *  var global = this;
1354                          *  function func() {
1355                          *      with({ eval: global.eval) { eval("var x = 10;") }
1356                          *  }
1357                          */
1358                         loadExpressionAsObject(ident.setIsNotFunction()); // Type.OBJECT as foo() makes no sense if foo == 3
1359                         globalIsEval();
1360                         method.ifeq(is_not_eval);
1361 
1362                         // Load up self (scope).
1363                         method.loadCompilerConstant(SCOPE);
1364                         final List<Expression> evalArgs = callNode.getEvalArgs().getArgs();
1365                         // load evaluated code
1366                         loadExpressionAsObject(evalArgs.get(0));
1367                         // load second and subsequent args for side-effect
1368                         final int numArgs = evalArgs.size();
1369                         for (int i = 1; i < numArgs; i++) {
1370                             loadAndDiscard(evalArgs.get(i));
1371                         }
1372                         method._goto(invoke_direct_eval);
1373 
1374                         method.label(is_not_eval);
1375                         // load this time but with dyn:getMethod|getProp|getElem
1376                         loadExpressionAsObject(ident); // Type.OBJECT as foo() makes no sense if foo == 3
1377                         // This is some scope 'eval' or global eval replaced by user
1378                         // but not the built-in ECMAScript 'eval' function call
1379                         method.loadNull();
1380                         argsCount = loadArgs(callNode.getArgs());
1381                     }
1382 
1383                     @Override
1384                     void consumeStack() {
1385                         // Ordinary call
1386                         dynamicCall(2 + argsCount, flags);
1387                         method._goto(eval_done);
1388 
1389                         method.label(invoke_direct_eval);
1390                         // Special/extra 'eval' arguments. These can be loaded late (in consumeStack) as we know none of
1391                         // them can ever be optimistic.
1392                         method.loadCompilerConstant(THIS);
1393                         method.load(callNode.getEvalArgs().getLocation());
1394                         method.load(CodeGenerator.this.lc.getCurrentFunction().isStrict());
1395                         // direct call to Global.directEval
1396                         globalDirectEval();
1397                         convertOptimisticReturnValue();
1398                         coerceStackTop(resultBounds);
1399                     }
1400                 }.emit();
1401 
1402                 method.label(eval_done);
1403             }
1404 
1405             @Override
1406             public boolean enterIdentNode(final IdentNode node) {
1407                 final Symbol symbol = node.getSymbol();
1408 
1409                 if (symbol.isScope()) {
1410                     final int flags = getCallSiteFlags() | CALLSITE_SCOPE;
1411                     final int useCount = symbol.getUseCount();
1412 
1413                     // Threshold for generating shared scope callsite is lower for fast scope symbols because we know
1414                     // we can dial in the correct scope. However, we also need to enable it for non-fast scopes to
1415                     // support huge scripts like mandreel.js.
1416                     if (callNode.isEval()) {
1417                         evalCall(node, flags);
1418                     } else if (useCount <= SharedScopeCall.FAST_SCOPE_CALL_THRESHOLD
1419                             || !isFastScope(symbol) && useCount <= SharedScopeCall.SLOW_SCOPE_CALL_THRESHOLD
1420                             || CodeGenerator.this.lc.inDynamicScope()
1421                             || isOptimisticOrRestOf()) {
1422                         scopeCall(node, flags);
1423                     } else {
1424                         sharedScopeCall(node, flags);
1425                     }
1426                     assert method.peekType().equals(resultBounds.within(callNode.getType())) : method.peekType() + " != " + resultBounds + "(" + callNode.getType() + ")";
1427                 } else {
1428                     enterDefault(node);
1429                 }
1430 
1431                 return false;
1432             }
1433 
1434             @Override
1435             public boolean enterAccessNode(final AccessNode node) {
1436                 //check if this is an apply to call node. only real applies, that haven't been
1437                 //shadowed from their way to the global scope counts
1438 
1439                 //call nodes have program points.
1440 
1441                 final int flags = getCallSiteFlags() | (callNode.isApplyToCall() ? CALLSITE_APPLY_TO_CALL : 0);
1442 
1443                 new OptimisticOperation(callNode, resultBounds) {
1444                     int argCount;
1445                     @Override
1446                     void loadStack() {
1447                         loadExpressionAsObject(node.getBase());
1448                         method.dup();
1449                         // NOTE: not using a nested OptimisticOperation on this dynamicGet, as we expect to get back
1450                         // a callable object. Nobody in their right mind would optimistically type this call site.
1451                         assert !node.isOptimistic();
1452                         method.dynamicGet(node.getType(), node.getProperty(), flags, true, node.isIndex());
1453                         method.swap();
1454                         argCount = loadArgs(args);
1455                     }
1456                     @Override
1457                     void consumeStack() {
1458                         dynamicCall(2 + argCount, flags);
1459                     }
1460                 }.emit();
1461 
1462                 return false;
1463             }
1464 
1465             @Override
1466             public boolean enterFunctionNode(final FunctionNode origCallee) {
1467                 new OptimisticOperation(callNode, resultBounds) {
1468                     FunctionNode callee;
1469                     int argsCount;
1470                     @Override
1471                     void loadStack() {
1472                         callee = (FunctionNode)origCallee.accept(CodeGenerator.this);
1473                         if (callee.isStrict()) { // "this" is undefined
1474                             method.loadUndefined(Type.OBJECT);
1475                         } else { // get global from scope (which is the self)
1476                             globalInstance();
1477                         }
1478                         argsCount = loadArgs(args);
1479                     }
1480 
1481                     @Override
1482                     void consumeStack() {
1483                         final int flags = getCallSiteFlags();
1484                         //assert callNodeType.equals(callee.getReturnType()) : callNodeType + " != " + callee.getReturnType();
1485                         dynamicCall(2 + argsCount, flags);
1486                     }
1487                 }.emit();
1488                 return false;
1489             }
1490 
1491             @Override
1492             public boolean enterIndexNode(final IndexNode node) {
1493                 new OptimisticOperation(callNode, resultBounds) {
1494                     int argsCount;
1495                     @Override
1496                     void loadStack() {
1497                         loadExpressionAsObject(node.getBase());
1498                         method.dup();
1499                         final Type indexType = node.getIndex().getType();
1500                         if (indexType.isObject() || indexType.isBoolean()) {
1501                             loadExpressionAsObject(node.getIndex()); //TODO boolean
1502                         } else {
1503                             loadExpressionUnbounded(node.getIndex());
1504                         }
1505                         // NOTE: not using a nested OptimisticOperation on this dynamicGetIndex, as we expect to get
1506                         // back a callable object. Nobody in their right mind would optimistically type this call site.
1507                         assert !node.isOptimistic();
1508                         method.dynamicGetIndex(node.getType(), getCallSiteFlags(), true);
1509                         method.swap();
1510                         argsCount = loadArgs(args);
1511                     }
1512                     @Override
1513                     void consumeStack() {
1514                         final int flags = getCallSiteFlags();
1515                         dynamicCall(2 + argsCount, flags);
1516                     }
1517                 }.emit();
1518                 return false;
1519             }
1520 
1521             @Override
1522             protected boolean enterDefault(final Node node) {
1523                 new OptimisticOperation(callNode, resultBounds) {
1524                     int argsCount;
1525                     @Override
1526                     void loadStack() {
1527                         // Load up function.
1528                         loadExpressionAsObject(function); //TODO, e.g. booleans can be used as functions
1529                         method.loadUndefined(Type.OBJECT); // ScriptFunction will figure out the correct this when it sees CALLSITE_SCOPE
1530                         argsCount = loadArgs(args);
1531                         }
1532                         @Override
1533                         void consumeStack() {
1534                             final int flags = getCallSiteFlags() | CALLSITE_SCOPE;
1535                             dynamicCall(2 + argsCount, flags);
1536                         }
1537                 }.emit();
1538                 return false;
1539             }
1540         });
1541 
1542         return false;
1543     }
1544 
1545     /**
1546      * Returns the flags with optimistic flag and program point removed.
1547      * @param flags the flags that need optimism stripped from them.
1548      * @return flags without optimism
1549      */
1550     static int nonOptimisticFlags(final int flags) {
1551         return flags & ~(CALLSITE_OPTIMISTIC | -1 << CALLSITE_PROGRAM_POINT_SHIFT);
1552     }
1553 
1554     @Override
1555     public boolean enterContinueNode(final ContinueNode continueNode) {
1556         return enterJumpStatement(continueNode);
1557     }
1558 
1559     @Override
1560     public boolean enterEmptyNode(final EmptyNode emptyNode) {
1561         if(!method.isReachable()) {
1562             return false;
1563         }
1564         enterStatement(emptyNode);
1565 
1566         return false;
1567     }
1568 
1569     @Override
1570     public boolean enterExpressionStatement(final ExpressionStatement expressionStatement) {
1571         if(!method.isReachable()) {
1572             return false;
1573         }
1574         enterStatement(expressionStatement);
1575 
1576         loadAndDiscard(expressionStatement.getExpression());
1577         assert method.getStackSize() == 0;
1578 
1579         return false;
1580     }
1581 
1582     @Override
1583     public boolean enterBlockStatement(final BlockStatement blockStatement) {
1584         if(!method.isReachable()) {
1585             return false;
1586         }
1587         enterStatement(blockStatement);
1588 
1589         blockStatement.getBlock().accept(this);
1590 
1591         return false;
1592     }
1593 
1594     @Override
1595     public boolean enterForNode(final ForNode forNode) {
1596         if(!method.isReachable()) {
1597             return false;
1598         }
1599         enterStatement(forNode);
1600         if (forNode.isForIn()) {
1601             enterForIn(forNode);
1602         } else {
1603             final Expression init = forNode.getInit();
1604             if (init != null) {
1605                 loadAndDiscard(init);
1606             }
1607             enterForOrWhile(forNode, forNode.getModify());
1608         }
1609 
1610         return false;
1611     }
1612 
1613     private void enterForIn(final ForNode forNode) {
1614         loadExpression(forNode.getModify(), TypeBounds.OBJECT);
1615         method.invoke(forNode.isForEach() ? ScriptRuntime.TO_VALUE_ITERATOR : ScriptRuntime.TO_PROPERTY_ITERATOR);
1616         final Symbol iterSymbol = forNode.getIterator();
1617         final int iterSlot = iterSymbol.getSlot(Type.OBJECT);
1618         method.store(iterSymbol, ITERATOR_TYPE);
1619 
1620         method.beforeJoinPoint(forNode);
1621 
1622         final Label continueLabel = forNode.getContinueLabel();
1623         final Label breakLabel    = forNode.getBreakLabel();
1624 
1625         method.label(continueLabel);
1626         method.load(ITERATOR_TYPE, iterSlot);
1627         method.invoke(interfaceCallNoLookup(ITERATOR_CLASS, "hasNext", boolean.class));
1628         final JoinPredecessorExpression test = forNode.getTest();
1629         final Block body = forNode.getBody();
1630         if(LocalVariableConversion.hasLiveConversion(test)) {
1631             final Label afterConversion = new Label("for_in_after_test_conv");
1632             method.ifne(afterConversion);
1633             method.beforeJoinPoint(test);
1634             method._goto(breakLabel);
1635             method.label(afterConversion);
1636         } else {
1637             method.ifeq(breakLabel);
1638         }
1639 
1640         new Store<Expression>(forNode.getInit()) {
1641             @Override
1642             protected void storeNonDiscard() {
1643                 // This expression is neither part of a discard, nor needs to be left on the stack after it was
1644                 // stored, so we override storeNonDiscard to be a no-op.
1645             }
1646 
1647             @Override
1648             protected void evaluate() {
1649                 new OptimisticOperation((Optimistic)forNode.getInit(), TypeBounds.UNBOUNDED) {
1650                     @Override
1651                     void loadStack() {
1652                         method.load(ITERATOR_TYPE, iterSlot);
1653                     }
1654 
1655                     @Override
1656                     void consumeStack() {
1657                         method.invoke(interfaceCallNoLookup(ITERATOR_CLASS, "next", Object.class));
1658                         convertOptimisticReturnValue();
1659                     }
1660                 }.emit();
1661             }
1662         }.store();
1663         body.accept(this);
1664 
1665         if(method.isReachable()) {
1666             method._goto(continueLabel);
1667         }
1668         method.label(breakLabel);
1669     }
1670 
1671     /**
1672      * Initialize the slots in a frame to undefined.
1673      *
1674      * @param block block with local vars.
1675      */
1676     private void initLocals(final Block block) {
1677         lc.onEnterBlock(block);
1678 
1679         final boolean isFunctionBody = lc.isFunctionBody();
1680         final FunctionNode function = lc.getCurrentFunction();
1681         if (isFunctionBody) {
1682             initializeMethodParameters(function);
1683             if(!function.isVarArg()) {
1684                 expandParameterSlots(function);
1685             }
1686             if (method.hasScope()) {
1687                 if (function.needsParentScope()) {
1688                     method.loadCompilerConstant(CALLEE);
1689                     method.invoke(ScriptFunction.GET_SCOPE);
1690                 } else {
1691                     assert function.hasScopeBlock();
1692                     method.loadNull();
1693                 }
1694                 method.storeCompilerConstant(SCOPE);
1695             }
1696             if (function.needsArguments()) {
1697                 initArguments(function);
1698             }
1699         }
1700 
1701         /*
1702          * Determine if block needs scope, if not, just do initSymbols for this block.
1703          */
1704         if (block.needsScope()) {
1705             /*
1706              * Determine if function is varargs and consequently variables have to
1707              * be in the scope.
1708              */
1709             final boolean varsInScope = function.allVarsInScope();
1710 
1711             // TODO for LET we can do better: if *block* does not contain any eval/with, we don't need its vars in scope.
1712 
1713             final boolean hasArguments = function.needsArguments();
1714             final List<MapTuple<Symbol>> tuples = new ArrayList<>();
1715             final Iterator<IdentNode> paramIter = function.getParameters().iterator();
1716             for (final Symbol symbol : block.getSymbols()) {
1717                 if (symbol.isInternal() || symbol.isThis()) {
1718                     continue;
1719                 }
1720 
1721                 if (symbol.isVar()) {
1722                     assert !varsInScope || symbol.isScope();
1723                     if (varsInScope || symbol.isScope()) {
1724                         assert symbol.isScope()   : "scope for " + symbol + " should have been set in Lower already " + function.getName();
1725                         assert !symbol.hasSlot()  : "slot for " + symbol + " should have been removed in Lower already" + function.getName();
1726 
1727                         //this tuple will not be put fielded, as it has no value, just a symbol
1728                         tuples.add(new MapTuple<Symbol>(symbol.getName(), symbol, null));
1729                     } else {
1730                         assert symbol.hasSlot() || symbol.slotCount() == 0 : symbol + " should have a slot only, no scope";
1731                     }
1732                 } else if (symbol.isParam() && (varsInScope || hasArguments || symbol.isScope())) {
1733                     assert symbol.isScope()   : "scope for " + symbol + " should have been set in AssignSymbols already " + function.getName() + " varsInScope="+varsInScope+" hasArguments="+hasArguments+" symbol.isScope()=" + symbol.isScope();
1734                     assert !(hasArguments && symbol.hasSlot())  : "slot for " + symbol + " should have been removed in Lower already " + function.getName();
1735 
1736                     final Type   paramType;
1737                     final Symbol paramSymbol;
1738 
1739                     if (hasArguments) {
1740                         assert !symbol.hasSlot()  : "slot for " + symbol + " should have been removed in Lower already ";
1741                         paramSymbol = null;
1742                         paramType   = null;
1743                     } else {
1744                         paramSymbol = symbol;
1745                         // NOTE: We're relying on the fact here that Block.symbols is a LinkedHashMap, hence it will
1746                         // return symbols in the order they were defined, and parameters are defined in the same order
1747                         // they appear in the function. That's why we can have a single pass over the parameter list
1748                         // with an iterator, always just scanning forward for the next parameter that matches the symbol
1749                         // name.
1750                         for(;;) {
1751                             final IdentNode nextParam = paramIter.next();
1752                             if(nextParam.getName().equals(symbol.getName())) {
1753                                 paramType = nextParam.getType();
1754                                 break;
1755                             }
1756                         }
1757                     }
1758 
1759                     tuples.add(new MapTuple<Symbol>(symbol.getName(), symbol, paramType, paramSymbol) {
1760                         //this symbol will be put fielded, we can't initialize it as undefined with a known type
1761                         @Override
1762                         public Class<?> getValueType() {
1763                             if (OBJECT_FIELDS_ONLY || value == null || paramType == null) {
1764                                 return Object.class;
1765                             }
1766                             return paramType.isBoolean() ? Object.class : paramType.getTypeClass();
1767                         }
1768                     });
1769                 }
1770             }
1771 
1772             /*
1773              * Create a new object based on the symbols and values, generate
1774              * bootstrap code for object
1775              */
1776             new FieldObjectCreator<Symbol>(this, tuples, true, hasArguments) {
1777                 @Override
1778                 protected void loadValue(final Symbol value, final Type type) {
1779                     method.load(value, type);
1780                 }
1781             }.makeObject(method);
1782             // program function: merge scope into global
1783             if (isFunctionBody && function.isProgram()) {
1784                 method.invoke(ScriptRuntime.MERGE_SCOPE);
1785             }
1786 
1787             method.storeCompilerConstant(SCOPE);
1788             if(!isFunctionBody) {
1789                 // Function body doesn't need a try/catch to restore scope, as it'd be a dead store anyway. Allowing it
1790                 // actually causes issues with UnwarrantedOptimismException handlers as ASM will sort this handler to
1791                 // the top of the exception handler table, so it'll be triggered instead of the UOE handlers.
1792                 final Label scopeEntryLabel = new Label("scope_entry");
1793                 scopeEntryLabels.push(scopeEntryLabel);
1794                 method.label(scopeEntryLabel);
1795             }
1796         } else if (isFunctionBody && function.isVarArg()) {
1797             // Since we don't have a scope, parameters didn't get assigned array indices by the FieldObjectCreator, so
1798             // we need to assign them separately here.
1799             int nextParam = 0;
1800             for (final IdentNode param : function.getParameters()) {
1801                 param.getSymbol().setFieldIndex(nextParam++);
1802             }
1803         }
1804 
1805         // Debugging: print symbols? @see --print-symbols flag
1806         printSymbols(block, function, (isFunctionBody ? "Function " : "Block in ") + (function.getIdent() == null ? "<anonymous>" : function.getIdent().getName()));
1807     }
1808 
1809     /**
1810      * Incoming method parameters are always declared on method entry; declare them in the local variable table.
1811      * @param function function for which code is being generated.
1812      */
1813     private void initializeMethodParameters(final FunctionNode function) {
1814         final Label functionStart = new Label("fn_start");
1815         method.label(functionStart);
1816         int nextSlot = 0;
1817         if(function.needsCallee()) {
1818             initializeInternalFunctionParameter(CALLEE, function, functionStart, nextSlot++);
1819         }
1820         initializeInternalFunctionParameter(THIS, function, functionStart, nextSlot++);
1821         if(function.isVarArg()) {
1822             initializeInternalFunctionParameter(VARARGS, function, functionStart, nextSlot++);
1823         } else {
1824             for(final IdentNode param: function.getParameters()) {
1825                 final Symbol symbol = param.getSymbol();
1826                 if(symbol.isBytecodeLocal()) {
1827                     method.initializeMethodParameter(symbol, param.getType(), functionStart);
1828                 }
1829             }
1830         }
1831     }
1832 
1833     private void initializeInternalFunctionParameter(final CompilerConstants cc, final FunctionNode fn, final Label functionStart, final int slot) {
1834         final Symbol symbol = initializeInternalFunctionOrSplitParameter(cc, fn, functionStart, slot);
1835         // Internal function params (:callee, this, and :varargs) are never expanded to multiple slots
1836         assert symbol.getFirstSlot() == slot;
1837     }
1838 
1839     private Symbol initializeInternalFunctionOrSplitParameter(final CompilerConstants cc, final FunctionNode fn, final Label functionStart, final int slot) {
1840         final Symbol symbol = fn.getBody().getExistingSymbol(cc.symbolName());
1841         final Type type = Type.typeFor(cc.type());
1842         method.initializeMethodParameter(symbol, type, functionStart);
1843         method.onLocalStore(type, slot);
1844         return symbol;
1845     }
1846 
1847     /**
1848      * Parameters come into the method packed into local variable slots next to each other. Nashorn on the other hand
1849      * can use 1-6 slots for a local variable depending on all the types it needs to store. When this method is invoked,
1850      * the symbols are already allocated such wider slots, but the values are still in tightly packed incoming slots,
1851      * and we need to spread them into their new locations.
1852      * @param function the function for which parameter-spreading code needs to be emitted
1853      */
1854     private void expandParameterSlots(final FunctionNode function) {
1855         final List<IdentNode> parameters = function.getParameters();
1856         // Calculate the total number of incoming parameter slots
1857         int currentIncomingSlot = function.needsCallee() ? 2 : 1;
1858         for(final IdentNode parameter: parameters) {
1859             currentIncomingSlot += parameter.getType().getSlots();
1860         }
1861         // Starting from last parameter going backwards, move the parameter values into their new slots.
1862         for(int i = parameters.size(); i-- > 0;) {
1863             final IdentNode parameter = parameters.get(i);
1864             final Type parameterType = parameter.getType();
1865             final int typeWidth = parameterType.getSlots();
1866             currentIncomingSlot -= typeWidth;
1867             final Symbol symbol = parameter.getSymbol();
1868             final int slotCount = symbol.slotCount();
1869             assert slotCount > 0;
1870             // Scoped parameters must not hold more than one value
1871             assert symbol.isBytecodeLocal() || slotCount == typeWidth;
1872 
1873             // Mark it as having its value stored into it by the method invocation.
1874             method.onLocalStore(parameterType, currentIncomingSlot);
1875             if(currentIncomingSlot != symbol.getSlot(parameterType)) {
1876                 method.load(parameterType, currentIncomingSlot);
1877                 method.store(symbol, parameterType);
1878             }
1879         }
1880     }
1881 
1882     private void initArguments(final FunctionNode function) {
1883         method.loadCompilerConstant(VARARGS);
1884         if (function.needsCallee()) {
1885             method.loadCompilerConstant(CALLEE);
1886         } else {
1887             // If function is strict mode, "arguments.callee" is not populated, so we don't necessarily need the
1888             // caller.
1889             assert function.isStrict();
1890             method.loadNull();
1891         }
1892         method.load(function.getParameters().size());
1893         globalAllocateArguments();
1894         method.storeCompilerConstant(ARGUMENTS);
1895     }
1896 
1897     private boolean skipFunction(final FunctionNode functionNode) {
1898         final ScriptEnvironment env = compiler.getScriptEnvironment();
1899         final boolean lazy = env._lazy_compilation;
1900         final boolean onDemand = compiler.isOnDemandCompilation();
1901 
1902         // If this is on-demand or lazy compilation, don't compile a nested (not topmost) function.
1903         if((onDemand || lazy) && lc.getOutermostFunction() != functionNode) {
1904             return true;
1905         }
1906 
1907         // If lazy compiling with optimistic types, don't compile the program eagerly either. It will soon be
1908         // invalidated anyway. In presence of a class cache, this further means that an obsoleted program version
1909         // lingers around. Also, currently loading previously persisted optimistic types information only works if
1910         // we're on-demand compiling a function, so with this strategy the :program method can also have the warmup
1911         // benefit of using previously persisted types.
1912         //
1913         // NOTE that this means the first compiled class will effectively just have a :createProgramFunction method, and
1914         // the RecompilableScriptFunctionData (RSFD) object in its constants array. It won't even have the :program
1915         // method. This is by design. It does mean that we're wasting one compiler execution (and we could minimize this
1916         // by just running it up to scope depth calculation, which creates the RSFDs and then this limited codegen).
1917         // We could emit an initial separate compile unit with the initial version of :program in it to better utilize
1918         // the compilation pipeline, but that would need more invasive changes, as currently the assumption that
1919         // :program is emitted into the first compilation unit of the function lives in many places.
1920         return !onDemand && lazy && env._optimistic_types && functionNode.isProgram();
1921     }
1922 
1923     @Override
1924     public boolean enterFunctionNode(final FunctionNode functionNode) {
1925         final int fnId = functionNode.getId();
1926 
1927         if (skipFunction(functionNode)) {
1928             // In case we are not generating code for the function, we must create or retrieve the function object and
1929             // load it on the stack here.
1930             newFunctionObject(functionNode, false);
1931             return false;
1932         }
1933 
1934         final String fnName = functionNode.getName();
1935 
1936         // NOTE: we only emit the method for a function with the given name once. We can have multiple functions with
1937         // the same name as a result of inlining finally blocks. However, in the future -- with type specialization,
1938         // notably -- we might need to check for both name *and* signature. Of course, even that might not be
1939         // sufficient; the function might have a code dependency on the type of the variables in its enclosing scopes,
1940         // and the type of such a variable can be different in catch and finally blocks. So, in the future we will have
1941         // to decide to either generate a unique method for each inlined copy of the function, maybe figure out its
1942         // exact type closure and deduplicate based on that, or just decide that functions in finally blocks aren't
1943         // worth it, and generate one method with most generic type closure.
1944         if (!emittedMethods.contains(fnName)) {
1945             log.info("=== BEGIN ", fnName);
1946 
1947             assert functionNode.getCompileUnit() != null : "no compile unit for " + fnName + " " + Debug.id(functionNode);
1948             unit = lc.pushCompileUnit(functionNode.getCompileUnit());
1949             assert lc.hasCompileUnits();
1950 
1951             final ClassEmitter classEmitter = unit.getClassEmitter();
1952             pushMethodEmitter(isRestOf() ? classEmitter.restOfMethod(functionNode) : classEmitter.method(functionNode));
1953             method.setPreventUndefinedLoad();
1954             if(useOptimisticTypes()) {
1955                 lc.pushUnwarrantedOptimismHandlers();
1956             }
1957 
1958             // new method - reset last line number
1959             lastLineNumber = -1;
1960 
1961             method.begin();
1962 
1963             if (isRestOf()) {
1964                 final ContinuationInfo ci = new ContinuationInfo();
1965                 fnIdToContinuationInfo.put(fnId, ci);
1966                 method.gotoLoopStart(ci.getHandlerLabel());
1967             }
1968         }
1969 
1970         return true;
1971     }
1972 
1973     private void pushMethodEmitter(final MethodEmitter newMethod) {
1974         method = lc.pushMethodEmitter(newMethod);
1975         catchLabels.push(METHOD_BOUNDARY);
1976     }
1977 
1978     private void popMethodEmitter() {
1979         method = lc.popMethodEmitter(method);
1980         assert catchLabels.peek() == METHOD_BOUNDARY;
1981         catchLabels.pop();
1982     }
1983 
1984     @Override
1985     public Node leaveFunctionNode(final FunctionNode functionNode) {
1986         try {
1987             final boolean markOptimistic;
1988             if (emittedMethods.add(functionNode.getName())) {
1989                 markOptimistic = generateUnwarrantedOptimismExceptionHandlers(functionNode);
1990                 generateContinuationHandler();
1991                 method.end(); // wrap up this method
1992                 unit   = lc.popCompileUnit(functionNode.getCompileUnit());
1993                 popMethodEmitter();
1994                 log.info("=== END ", functionNode.getName());
1995             } else {
1996                 markOptimistic = false;
1997             }
1998 
1999             FunctionNode newFunctionNode = functionNode.setState(lc, CompilationState.BYTECODE_GENERATED);
2000             if (markOptimistic) {
2001                 newFunctionNode = newFunctionNode.setFlag(lc, FunctionNode.IS_DEOPTIMIZABLE);
2002             }
2003 
2004             newFunctionObject(newFunctionNode, true);
2005             return newFunctionNode;
2006         } catch (final Throwable t) {
2007             Context.printStackTrace(t);
2008             final VerifyError e = new VerifyError("Code generation bug in \"" + functionNode.getName() + "\": likely stack misaligned: " + t + " " + functionNode.getSource().getName());
2009             e.initCause(t);
2010             throw e;
2011         }
2012     }
2013 
2014     @Override
2015     public boolean enterIfNode(final IfNode ifNode) {
2016         if(!method.isReachable()) {
2017             return false;
2018         }
2019         enterStatement(ifNode);
2020 
2021         final Expression test = ifNode.getTest();
2022         final Block pass = ifNode.getPass();
2023         final Block fail = ifNode.getFail();
2024 
2025         if (Expression.isAlwaysTrue(test)) {
2026             loadAndDiscard(test);
2027             pass.accept(this);
2028             return false;
2029         } else if (Expression.isAlwaysFalse(test)) {
2030             loadAndDiscard(test);
2031             if (fail != null) {
2032                 fail.accept(this);
2033             }
2034             return false;
2035         }
2036 
2037         final boolean hasFailConversion = LocalVariableConversion.hasLiveConversion(ifNode);
2038 
2039         final Label failLabel  = new Label("if_fail");
2040         final Label afterLabel = (fail == null && !hasFailConversion) ? null : new Label("if_done");
2041 
2042         emitBranch(test, failLabel, false);
2043 
2044         pass.accept(this);
2045         if(method.isReachable() && afterLabel != null) {
2046             method._goto(afterLabel); //don't fallthru to fail block
2047         }
2048         method.label(failLabel);
2049 
2050         if (fail != null) {
2051             fail.accept(this);
2052         } else if(hasFailConversion) {
2053             method.beforeJoinPoint(ifNode);
2054         }
2055 
2056         if(afterLabel != null && afterLabel.isReachable()) {
2057             method.label(afterLabel);
2058         }
2059 
2060         return false;
2061     }
2062 
2063     private void emitBranch(final Expression test, final Label label, final boolean jumpWhenTrue) {
2064         new BranchOptimizer(this, method).execute(test, label, jumpWhenTrue);
2065     }
2066 
2067     private void enterStatement(final Statement statement) {
2068         lineNumber(statement);
2069     }
2070 
2071     private void lineNumber(final Statement statement) {
2072         lineNumber(statement.getLineNumber());
2073     }
2074 
2075     private void lineNumber(final int lineNumber) {
2076         if (lineNumber != lastLineNumber && lineNumber != Node.NO_LINE_NUMBER) {
2077             method.lineNumber(lineNumber);
2078             lastLineNumber = lineNumber;
2079         }
2080     }
2081 
2082     int getLastLineNumber() {
2083         return lastLineNumber;
2084     }
2085 
2086     /**
2087      * Load a list of nodes as an array of a specific type
2088      * The array will contain the visited nodes.
2089      *
2090      * @param arrayLiteralNode the array of contents
2091      * @param arrayType        the type of the array, e.g. ARRAY_NUMBER or ARRAY_OBJECT
2092      *
2093      * @return the method generator that was used
2094      */
2095     private MethodEmitter loadArray(final ArrayLiteralNode arrayLiteralNode, final ArrayType arrayType) {
2096         assert arrayType == Type.INT_ARRAY || arrayType == Type.LONG_ARRAY || arrayType == Type.NUMBER_ARRAY || arrayType == Type.OBJECT_ARRAY;
2097 
2098         final Expression[]    nodes    = arrayLiteralNode.getValue();
2099         final Object          presets  = arrayLiteralNode.getPresets();
2100         final int[]           postsets = arrayLiteralNode.getPostsets();
2101         final Class<?>        type     = arrayType.getTypeClass();
2102         final List<ArrayUnit> units    = arrayLiteralNode.getUnits();
2103 
2104         loadConstant(presets);
2105 
2106         final Type elementType = arrayType.getElementType();
2107 
2108         if (units != null) {
2109             final MethodEmitter savedMethod     = method;
2110             final FunctionNode  currentFunction = lc.getCurrentFunction();
2111 
2112             for (final ArrayUnit arrayUnit : units) {
2113                 unit = lc.pushCompileUnit(arrayUnit.getCompileUnit());
2114 
2115                 final String className = unit.getUnitClassName();
2116                 assert unit != null;
2117                 final String name      = currentFunction.uniqueName(SPLIT_PREFIX.symbolName());
2118                 final String signature = methodDescriptor(type, ScriptFunction.class, Object.class, ScriptObject.class, type);
2119 
2120                 pushMethodEmitter(unit.getClassEmitter().method(EnumSet.of(Flag.PUBLIC, Flag.STATIC), name, signature));
2121 
2122                 method.setFunctionNode(currentFunction);
2123                 method.begin();
2124 
2125                 defineCommonSplitMethodParameters();
2126                 defineSplitMethodParameter(CompilerConstants.SPLIT_ARRAY_ARG.slot(), arrayType);
2127 
2128                 // NOTE: when this is no longer needed, SplitIntoFunctions will no longer have to add IS_SPLIT
2129                 // to synthetic functions, and FunctionNode.needsCallee() will no longer need to test for isSplit().
2130                 final int arraySlot = fixScopeSlot(currentFunction, 3);
2131 
2132                 lc.enterSplitNode();
2133 
2134                 for (int i = arrayUnit.getLo(); i < arrayUnit.getHi(); i++) {
2135                     method.load(arrayType, arraySlot);
2136                     storeElement(nodes, elementType, postsets[i]);
2137                 }
2138 
2139                 method.load(arrayType, arraySlot);
2140                 method._return();
2141                 lc.exitSplitNode();
2142                 method.end();
2143                 lc.releaseSlots();
2144                 popMethodEmitter();
2145 
2146                 assert method == savedMethod;
2147                 method.loadCompilerConstant(CALLEE);
2148                 method.swap();
2149                 method.loadCompilerConstant(THIS);
2150                 method.swap();
2151                 method.loadCompilerConstant(SCOPE);
2152                 method.swap();
2153                 method.invokestatic(className, name, signature);
2154 
2155                 unit = lc.popCompileUnit(unit);
2156             }
2157 
2158             return method;
2159         }
2160 
2161         if(postsets.length > 0) {
2162             final int arraySlot = method.getUsedSlotsWithLiveTemporaries();
2163             method.storeTemp(arrayType, arraySlot);
2164             for (final int postset : postsets) {
2165                 method.load(arrayType, arraySlot);
2166                 storeElement(nodes, elementType, postset);
2167             }
2168             method.load(arrayType, arraySlot);
2169         }
2170         return method;
2171     }
2172 
2173     private void storeElement(final Expression[] nodes, final Type elementType, final int index) {
2174         method.load(index);
2175 
2176         final Expression element = nodes[index];
2177 
2178         if (element == null) {
2179             method.loadEmpty(elementType);
2180         } else {
2181             loadExpressionAsType(element, elementType);
2182         }
2183 
2184         method.arraystore();
2185     }
2186 
2187     private MethodEmitter loadArgsArray(final List<Expression> args) {
2188         final Object[] array = new Object[args.size()];
2189         loadConstant(array);
2190 
2191         for (int i = 0; i < args.size(); i++) {
2192             method.dup();
2193             method.load(i);
2194             loadExpression(args.get(i), TypeBounds.OBJECT); // variable arity methods always take objects
2195             method.arraystore();
2196         }
2197 
2198         return method;
2199     }
2200 
2201     /**
2202      * Load a constant from the constant array. This is only public to be callable from the objects
2203      * subpackage. Do not call directly.
2204      *
2205      * @param string string to load
2206      */
2207     void loadConstant(final String string) {
2208         final String       unitClassName = unit.getUnitClassName();
2209         final ClassEmitter classEmitter  = unit.getClassEmitter();
2210         final int          index         = compiler.getConstantData().add(string);
2211 
2212         method.load(index);
2213         method.invokestatic(unitClassName, GET_STRING.symbolName(), methodDescriptor(String.class, int.class));
2214         classEmitter.needGetConstantMethod(String.class);
2215     }
2216 
2217     /**
2218      * Load a constant from the constant array. This is only public to be callable from the objects
2219      * subpackage. Do not call directly.
2220      *
2221      * @param object object to load
2222      */
2223     void loadConstant(final Object object) {
2224         loadConstant(object, unit, method);
2225     }
2226 
2227     private void loadConstant(final Object object, final CompileUnit compileUnit, final MethodEmitter methodEmitter) {
2228         final String       unitClassName = compileUnit.getUnitClassName();
2229         final ClassEmitter classEmitter  = compileUnit.getClassEmitter();
2230         final int          index         = compiler.getConstantData().add(object);
2231         final Class<?>     cls           = object.getClass();
2232 
2233         if (cls == PropertyMap.class) {
2234             methodEmitter.load(index);
2235             methodEmitter.invokestatic(unitClassName, GET_MAP.symbolName(), methodDescriptor(PropertyMap.class, int.class));
2236             classEmitter.needGetConstantMethod(PropertyMap.class);
2237         } else if (cls.isArray()) {
2238             methodEmitter.load(index);
2239             final String methodName = ClassEmitter.getArrayMethodName(cls);
2240             methodEmitter.invokestatic(unitClassName, methodName, methodDescriptor(cls, int.class));
2241             classEmitter.needGetConstantMethod(cls);
2242         } else {
2243             methodEmitter.loadConstants().load(index).arrayload();
2244             if (object instanceof ArrayData) {
2245                 // avoid cast to non-public ArrayData subclass
2246                 methodEmitter.checkcast(ArrayData.class);
2247                 methodEmitter.invoke(virtualCallNoLookup(ArrayData.class, "copy", ArrayData.class));
2248             } else if (cls != Object.class) {
2249                 methodEmitter.checkcast(cls);
2250             }
2251         }
2252     }
2253 
2254     // literal values
2255     private void loadLiteral(final LiteralNode<?> node, final TypeBounds resultBounds) {
2256         final Object value = node.getValue();
2257 
2258         if (value == null) {
2259             method.loadNull();
2260         } else if (value instanceof Undefined) {
2261             method.loadUndefined(resultBounds.within(Type.OBJECT));
2262         } else if (value instanceof String) {
2263             final String string = (String)value;
2264 
2265             if (string.length() > MethodEmitter.LARGE_STRING_THRESHOLD / 3) { // 3 == max bytes per encoded char
2266                 loadConstant(string);
2267             } else {
2268                 method.load(string);
2269             }
2270         } else if (value instanceof RegexToken) {
2271             loadRegex((RegexToken)value);
2272         } else if (value instanceof Boolean) {
2273             method.load((Boolean)value);
2274         } else if (value instanceof Integer) {
2275             if(!resultBounds.canBeNarrowerThan(Type.OBJECT)) {
2276                 method.load((Integer)value);
2277                 method.convert(Type.OBJECT);
2278             } else if(!resultBounds.canBeNarrowerThan(Type.NUMBER)) {
2279                 method.load(((Integer)value).doubleValue());
2280             } else if(!resultBounds.canBeNarrowerThan(Type.LONG)) {
2281                 method.load(((Integer)value).longValue());
2282             } else {
2283                 method.load((Integer)value);
2284             }
2285         } else if (value instanceof Long) {
2286             if(!resultBounds.canBeNarrowerThan(Type.OBJECT)) {
2287                 method.load((Long)value);
2288                 method.convert(Type.OBJECT);
2289             } else if(!resultBounds.canBeNarrowerThan(Type.NUMBER)) {
2290                 method.load(((Long)value).doubleValue());
2291             } else {
2292                 method.load((Long)value);
2293             }
2294         } else if (value instanceof Double) {
2295             if(!resultBounds.canBeNarrowerThan(Type.OBJECT)) {
2296                 method.load((Double)value);
2297                 method.convert(Type.OBJECT);
2298             } else {
2299                 method.load((Double)value);
2300             }
2301         } else if (node instanceof ArrayLiteralNode) {
2302             final ArrayLiteralNode arrayLiteral = (ArrayLiteralNode)node;
2303             final ArrayType atype = arrayLiteral.getArrayType();
2304             loadArray(arrayLiteral, atype);
2305             globalAllocateArray(atype);
2306         } else {
2307             throw new UnsupportedOperationException("Unknown literal for " + node.getClass() + " " + value.getClass() + " " + value);
2308         }
2309     }
2310 
2311     private MethodEmitter loadRegexToken(final RegexToken value) {
2312         method.load(value.getExpression());
2313         method.load(value.getOptions());
2314         return globalNewRegExp();
2315     }
2316 
2317     private MethodEmitter loadRegex(final RegexToken regexToken) {
2318         if (regexFieldCount > MAX_REGEX_FIELDS) {
2319             return loadRegexToken(regexToken);
2320         }
2321         // emit field
2322         final String       regexName    = lc.getCurrentFunction().uniqueName(REGEX_PREFIX.symbolName());
2323         final ClassEmitter classEmitter = unit.getClassEmitter();
2324 
2325         classEmitter.field(EnumSet.of(PRIVATE, STATIC), regexName, Object.class);
2326         regexFieldCount++;
2327 
2328         // get field, if null create new regex, finally clone regex object
2329         method.getStatic(unit.getUnitClassName(), regexName, typeDescriptor(Object.class));
2330         method.dup();
2331         final Label cachedLabel = new Label("cached");
2332         method.ifnonnull(cachedLabel);
2333 
2334         method.pop();
2335         loadRegexToken(regexToken);
2336         method.dup();
2337         method.putStatic(unit.getUnitClassName(), regexName, typeDescriptor(Object.class));
2338 
2339         method.label(cachedLabel);
2340         globalRegExpCopy();
2341 
2342         return method;
2343     }
2344 
2345     /**
2346      * Check if a property value contains a particular program point
2347      * @param value value
2348      * @param pp    program point
2349      * @return true if it's there.
2350      */
2351     private static boolean propertyValueContains(final Expression value, final int pp) {
2352         return new Supplier<Boolean>() {
2353             boolean contains;
2354 
2355             @Override
2356             public Boolean get() {
2357                 value.accept(new NodeVisitor<LexicalContext>(new LexicalContext()) {
2358                     @Override
2359                     public boolean enterFunctionNode(final FunctionNode functionNode) {
2360                         return false;
2361                     }
2362 
2363                     @Override
2364                     public boolean enterObjectNode(final ObjectNode objectNode) {
2365                         return false;
2366                     }
2367 
2368                     @Override
2369                     public boolean enterDefault(final Node node) {
2370                         if (contains) {
2371                             return false;
2372                         }
2373                         if (node instanceof Optimistic && ((Optimistic)node).getProgramPoint() == pp) {
2374                             contains = true;
2375                             return false;
2376                         }
2377                         return true;
2378                     }
2379                 });
2380 
2381                 return contains;
2382             }
2383         }.get();
2384     }
2385 
2386     private void loadObjectNode(final ObjectNode objectNode) {
2387         final List<PropertyNode> elements = objectNode.getElements();
2388 
2389         final List<MapTuple<Expression>> tuples = new ArrayList<>();
2390         final List<PropertyNode> gettersSetters = new ArrayList<>();
2391         final int ccp = getCurrentContinuationEntryPoint();
2392 
2393         Expression protoNode = null;
2394         boolean restOfProperty = false;
2395 
2396         for (final PropertyNode propertyNode : elements) {
2397             final Expression value = propertyNode.getValue();
2398             final String key = propertyNode.getKeyName();
2399             // Just use a pseudo-symbol. We just need something non null; use the name and zero flags.
2400             final Symbol symbol = value == null ? null : new Symbol(key, 0);
2401 
2402             if (value == null) {
2403                 gettersSetters.add(propertyNode);
2404             } else if (propertyNode.getKey() instanceof IdentNode &&
2405                        key.equals(ScriptObject.PROTO_PROPERTY_NAME)) {
2406                 // ES6 draft compliant __proto__ inside object literal
2407                 // Identifier key and name is __proto__
2408                 protoNode = value;
2409                 continue;
2410             }
2411 
2412             restOfProperty |=
2413                 value != null &&
2414                 isValid(ccp) &&
2415                 propertyValueContains(value, ccp);
2416 
2417             //for literals, a value of null means object type, i.e. the value null or getter setter function
2418             //(I think)
2419             final Class<?> valueType = (OBJECT_FIELDS_ONLY || value == null || value.getType().isBoolean()) ? Object.class : value.getType().getTypeClass();
2420             tuples.add(new MapTuple<Expression>(key, symbol, Type.typeFor(valueType), value) {
2421                 @Override
2422                 public Class<?> getValueType() {
2423                     return type.getTypeClass();
2424                 }
2425             });
2426         }
2427 
2428         final ObjectCreator<?> oc;
2429         if (elements.size() > OBJECT_SPILL_THRESHOLD) {
2430             oc = new SpillObjectCreator(this, tuples);
2431         } else {
2432             oc = new FieldObjectCreator<Expression>(this, tuples) {
2433                 @Override
2434                 protected void loadValue(final Expression node, final Type type) {
2435                     loadExpressionAsType(node, type);
2436                 }};
2437         }
2438         oc.makeObject(method);
2439 
2440         //if this is a rest of method and our continuation point was found as one of the values
2441         //in the properties above, we need to reset the map to oc.getMap() in the continuation
2442         //handler
2443         if (restOfProperty) {
2444             final ContinuationInfo ci = getContinuationInfo();
2445             // Can be set at most once for a single rest-of method
2446             assert ci.getObjectLiteralMap() == null;
2447             ci.setObjectLiteralMap(oc.getMap());
2448             ci.setObjectLiteralStackDepth(method.getStackSize());
2449         }
2450 
2451         method.dup();
2452         if (protoNode != null) {
2453             loadExpressionAsObject(protoNode);
2454             // take care of { __proto__: 34 } or some such!
2455             method.convert(Type.OBJECT);
2456             method.invoke(ScriptObject.SET_PROTO_FROM_LITERAL);
2457         } else {
2458             method.invoke(ScriptObject.SET_GLOBAL_OBJECT_PROTO);
2459         }
2460 
2461         for (final PropertyNode propertyNode : gettersSetters) {
2462             final FunctionNode getter = propertyNode.getGetter();
2463             final FunctionNode setter = propertyNode.getSetter();
2464 
2465             assert getter != null || setter != null;
2466 
2467             method.dup().loadKey(propertyNode.getKey());
2468             if (getter == null) {
2469                 method.loadNull();
2470             } else {
2471                 getter.accept(this);
2472             }
2473 
2474             if (setter == null) {
2475                 method.loadNull();
2476             } else {
2477                 setter.accept(this);
2478             }
2479 
2480             method.invoke(ScriptObject.SET_USER_ACCESSORS);
2481         }
2482     }
2483 
2484     @Override
2485     public boolean enterReturnNode(final ReturnNode returnNode) {
2486         if(!method.isReachable()) {
2487             return false;
2488         }
2489         enterStatement(returnNode);
2490 
2491         method.registerReturn();
2492 
2493         final Type returnType = lc.getCurrentFunction().getReturnType();
2494 
2495         final Expression expression = returnNode.getExpression();
2496         if (expression != null) {
2497             loadExpressionUnbounded(expression);
2498         } else {
2499             method.loadUndefined(returnType);
2500         }
2501 
2502         method._return(returnType);
2503 
2504         return false;
2505     }
2506 
2507     private boolean undefinedCheck(final RuntimeNode runtimeNode, final List<Expression> args) {
2508         final Request request = runtimeNode.getRequest();
2509 
2510         if (!Request.isUndefinedCheck(request)) {
2511             return false;
2512         }
2513 
2514         final Expression lhs = args.get(0);
2515         final Expression rhs = args.get(1);
2516 
2517         final Symbol lhsSymbol = lhs instanceof IdentNode ? ((IdentNode)lhs).getSymbol() : null;
2518         final Symbol rhsSymbol = rhs instanceof IdentNode ? ((IdentNode)rhs).getSymbol() : null;
2519         // One must be a "undefined" identifier, otherwise we can't get here
2520         assert lhsSymbol != null || rhsSymbol != null;
2521 
2522         final Symbol undefinedSymbol;
2523         if (isUndefinedSymbol(lhsSymbol)) {
2524             undefinedSymbol = lhsSymbol;
2525         } else {
2526             assert isUndefinedSymbol(rhsSymbol);
2527             undefinedSymbol = rhsSymbol;
2528         }
2529 
2530         assert undefinedSymbol != null; //remove warning
2531         if (!undefinedSymbol.isScope()) {
2532             return false; //disallow undefined as local var or parameter
2533         }
2534 
2535         if (lhsSymbol == undefinedSymbol && lhs.getType().isPrimitive()) {
2536             //we load the undefined first. never mind, because this will deoptimize anyway
2537             return false;
2538         }
2539 
2540         if(isDeoptimizedExpression(lhs)) {
2541             // This is actually related to "lhs.getType().isPrimitive()" above: any expression being deoptimized in
2542             // the current chain of rest-of compilations used to have a type narrower than Object (so it was primitive).
2543             // We must not perform undefined check specialization for them, as then we'd violate the basic rule of
2544             // "Thou shalt not alter the stack shape between a deoptimized method and any of its (transitive) rest-ofs."
2545             return false;
2546         }
2547 
2548         //make sure that undefined has not been overridden or scoped as a local var
2549         //between us and global
2550         if (!compiler.isGlobalSymbol(lc.getCurrentFunction(), "undefined")) {
2551             return false;
2552         }
2553 
2554         final boolean isUndefinedCheck = request == Request.IS_UNDEFINED;
2555         final Expression expr = undefinedSymbol == lhsSymbol ? rhs : lhs;
2556         if (expr.getType().isPrimitive()) {
2557             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
2558             method.load(!isUndefinedCheck);
2559         } else {
2560             final Label checkTrue  = new Label("ud_check_true");
2561             final Label end        = new Label("end");
2562             loadExpressionAsObject(expr);
2563             method.loadUndefined(Type.OBJECT);
2564             method.if_acmpeq(checkTrue);
2565             method.load(!isUndefinedCheck);
2566             method._goto(end);
2567             method.label(checkTrue);
2568             method.load(isUndefinedCheck);
2569             method.label(end);
2570         }
2571 
2572         return true;
2573     }
2574 
2575     private static boolean isUndefinedSymbol(final Symbol symbol) {
2576         return symbol != null && "undefined".equals(symbol.getName());
2577     }
2578 
2579     private static boolean isNullLiteral(final Node node) {
2580         return node instanceof LiteralNode<?> && ((LiteralNode<?>) node).isNull();
2581     }
2582 
2583     private boolean nullCheck(final RuntimeNode runtimeNode, final List<Expression> args) {
2584         final Request request = runtimeNode.getRequest();
2585 
2586         if (!Request.isEQ(request) && !Request.isNE(request)) {
2587             return false;
2588         }
2589 
2590         assert args.size() == 2 : "EQ or NE or TYPEOF need two args";
2591 
2592         Expression lhs = args.get(0);
2593         Expression rhs = args.get(1);
2594 
2595         if (isNullLiteral(lhs)) {
2596             final Expression tmp = lhs;
2597             lhs = rhs;
2598             rhs = tmp;
2599         }
2600 
2601         if (!isNullLiteral(rhs)) {
2602             return false;
2603         }
2604 
2605         if (!lhs.getType().isObject()) {
2606             return false;
2607         }
2608 
2609         if(isDeoptimizedExpression(lhs)) {
2610             // This is actually related to "!lhs.getType().isObject()" above: any expression being deoptimized in
2611             // the current chain of rest-of compilations used to have a type narrower than Object. We must not
2612             // perform null check specialization for them, as then we'd no longer be loading aconst_null on stack
2613             // and thus violate the basic rule of "Thou shalt not alter the stack shape between a deoptimized
2614             // method and any of its (transitive) rest-ofs."
2615             // NOTE also that if we had a representation for well-known constants (e.g. null, 0, 1, -1, etc.) in
2616             // Label$Stack.localLoads then this wouldn't be an issue, as we would never (somewhat ridiculously)
2617             // allocate a temporary local to hold the result of aconst_null before attempting an optimistic
2618             // operation.
2619             return false;
2620         }
2621 
2622         // this is a null literal check, so if there is implicit coercion
2623         // involved like {D}x=null, we will fail - this is very rare
2624         final Label trueLabel  = new Label("trueLabel");
2625         final Label falseLabel = new Label("falseLabel");
2626         final Label endLabel   = new Label("end");
2627 
2628         loadExpressionUnbounded(lhs);    //lhs
2629         final Label popLabel;
2630         if (!Request.isStrict(request)) {
2631             method.dup(); //lhs lhs
2632             popLabel = new Label("pop");
2633         } else {
2634             popLabel = null;
2635         }
2636 
2637         if (Request.isEQ(request)) {
2638             method.ifnull(!Request.isStrict(request) ? popLabel : trueLabel);
2639             if (!Request.isStrict(request)) {
2640                 method.loadUndefined(Type.OBJECT);
2641                 method.if_acmpeq(trueLabel);
2642             }
2643             method.label(falseLabel);
2644             method.load(false);
2645             method._goto(endLabel);
2646             if (!Request.isStrict(request)) {
2647                 method.label(popLabel);
2648                 method.pop();
2649             }
2650             method.label(trueLabel);
2651             method.load(true);
2652             method.label(endLabel);
2653         } else if (Request.isNE(request)) {
2654             method.ifnull(!Request.isStrict(request) ? popLabel : falseLabel);
2655             if (!Request.isStrict(request)) {
2656                 method.loadUndefined(Type.OBJECT);
2657                 method.if_acmpeq(falseLabel);
2658             }
2659             method.label(trueLabel);
2660             method.load(true);
2661             method._goto(endLabel);
2662             if (!Request.isStrict(request)) {
2663                 method.label(popLabel);
2664                 method.pop();
2665             }
2666             method.label(falseLabel);
2667             method.load(false);
2668             method.label(endLabel);
2669         }
2670 
2671         assert runtimeNode.getType().isBoolean();
2672         method.convert(runtimeNode.getType());
2673 
2674         return true;
2675     }
2676 
2677     /**
2678      * Was this expression or any of its subexpressions deoptimized in the current recompilation chain of rest-of methods?
2679      * @param rootExpr the expression being tested
2680      * @return true if the expression or any of its subexpressions was deoptimized in the current recompilation chain.
2681      */
2682     private boolean isDeoptimizedExpression(final Expression rootExpr) {
2683         if(!isRestOf()) {
2684             return false;
2685         }
2686         return new Supplier<Boolean>() {
2687             boolean contains;
2688             @Override
2689             public Boolean get() {
2690                 rootExpr.accept(new NodeVisitor<LexicalContext>(new LexicalContext()) {
2691                     @Override
2692                     public boolean enterFunctionNode(final FunctionNode functionNode) {
2693                         return false;
2694                     }
2695                     @Override
2696                     public boolean enterDefault(final Node node) {
2697                         if(!contains && node instanceof Optimistic) {
2698                             final int pp = ((Optimistic)node).getProgramPoint();
2699                             contains = isValid(pp) && isContinuationEntryPoint(pp);
2700                         }
2701                         return !contains;
2702                     }
2703                 });
2704                 return contains;
2705             }
2706         }.get();
2707     }
2708 
2709     private void loadRuntimeNode(final RuntimeNode runtimeNode) {
2710         final List<Expression> args = new ArrayList<>(runtimeNode.getArgs());
2711         if (nullCheck(runtimeNode, args)) {
2712            return;
2713         } else if(undefinedCheck(runtimeNode, args)) {
2714             return;
2715         }
2716         // Revert a false undefined check to a strict equality check
2717         final RuntimeNode newRuntimeNode;
2718         final Request request = runtimeNode.getRequest();
2719         if (Request.isUndefinedCheck(request)) {
2720             newRuntimeNode = runtimeNode.setRequest(request == Request.IS_UNDEFINED ? Request.EQ_STRICT : Request.NE_STRICT);
2721         } else {
2722             newRuntimeNode = runtimeNode;
2723         }
2724 
2725         new OptimisticOperation(newRuntimeNode, TypeBounds.UNBOUNDED) {
2726             @Override
2727             void loadStack() {
2728                 for (final Expression arg : args) {
2729                     loadExpression(arg, TypeBounds.OBJECT);
2730                 }
2731             }
2732             @Override
2733             void consumeStack() {
2734                 method.invokestatic(
2735                         CompilerConstants.className(ScriptRuntime.class),
2736                         newRuntimeNode.getRequest().toString(),
2737                         new FunctionSignature(
2738                             false,
2739                             false,
2740                             newRuntimeNode.getType(),
2741                             args.size()).toString());
2742             }
2743         }.emit();
2744 
2745         method.convert(newRuntimeNode.getType());
2746     }
2747 
2748     private void defineCommonSplitMethodParameters() {
2749         defineSplitMethodParameter(0, CALLEE);
2750         defineSplitMethodParameter(1, THIS);
2751         defineSplitMethodParameter(2, SCOPE);
2752     }
2753 
2754     private void defineSplitMethodParameter(final int slot, final CompilerConstants cc) {
2755         defineSplitMethodParameter(slot, Type.typeFor(cc.type()));
2756     }
2757 
2758     private void defineSplitMethodParameter(final int slot, final Type type) {
2759         method.defineBlockLocalVariable(slot, slot + type.getSlots());
2760         method.onLocalStore(type, slot);
2761     }
2762 
2763     private int fixScopeSlot(final FunctionNode functionNode, final int extraSlot) {
2764         // TODO hack to move the scope to the expected slot (needed because split methods reuse the same slots as the root method)
2765         final int actualScopeSlot = functionNode.compilerConstant(SCOPE).getSlot(SCOPE_TYPE);
2766         final int defaultScopeSlot = SCOPE.slot();
2767         int newExtraSlot = extraSlot;
2768         if (actualScopeSlot != defaultScopeSlot) {
2769             if (actualScopeSlot == extraSlot) {
2770                 newExtraSlot = extraSlot + 1;
2771                 method.defineBlockLocalVariable(newExtraSlot, newExtraSlot + 1);
2772                 method.load(Type.OBJECT, extraSlot);
2773                 method.storeHidden(Type.OBJECT, newExtraSlot);
2774             } else {
2775                 method.defineBlockLocalVariable(actualScopeSlot, actualScopeSlot + 1);
2776             }
2777             method.load(SCOPE_TYPE, defaultScopeSlot);
2778             method.storeCompilerConstant(SCOPE);
2779         }
2780         return newExtraSlot;
2781     }
2782 
2783     @Override
2784     public boolean enterSplitReturn(final SplitReturn splitReturn) {
2785         if (method.isReachable()) {
2786             method.loadUndefined(lc.getCurrentFunction().getReturnType())._return();
2787         }
2788         return false;
2789     }
2790 
2791     @Override
2792     public boolean enterSetSplitState(final SetSplitState setSplitState) {
2793         if (method.isReachable()) {
2794             method.setSplitState(setSplitState.getState());
2795         }
2796         return false;
2797     }
2798 
2799     @Override
2800     public boolean enterSwitchNode(final SwitchNode switchNode) {
2801         if(!method.isReachable()) {
2802             return false;
2803         }
2804         enterStatement(switchNode);
2805 
2806         final Expression     expression  = switchNode.getExpression();
2807         final List<CaseNode> cases       = switchNode.getCases();
2808 
2809         if (cases.isEmpty()) {
2810             // still evaluate expression for side-effects.
2811             loadAndDiscard(expression);
2812             return false;
2813         }
2814 
2815         final CaseNode defaultCase       = switchNode.getDefaultCase();
2816         final Label    breakLabel        = switchNode.getBreakLabel();
2817         final int      liveLocalsOnBreak = method.getUsedSlotsWithLiveTemporaries();
2818 
2819         if (defaultCase != null && cases.size() == 1) {
2820             // default case only
2821             assert cases.get(0) == defaultCase;
2822             loadAndDiscard(expression);
2823             defaultCase.getBody().accept(this);
2824             method.breakLabel(breakLabel, liveLocalsOnBreak);
2825             return false;
2826         }
2827 
2828         // NOTE: it can still change in the tableswitch/lookupswitch case if there's no default case
2829         // but we need to add a synthetic default case for local variable conversions
2830         Label defaultLabel = defaultCase != null ? defaultCase.getEntry() : breakLabel;
2831         final boolean hasSkipConversion = LocalVariableConversion.hasLiveConversion(switchNode);
2832 
2833         if (switchNode.isUniqueInteger()) {
2834             // Tree for sorting values.
2835             final TreeMap<Integer, Label> tree = new TreeMap<>();
2836 
2837             // Build up sorted tree.
2838             for (final CaseNode caseNode : cases) {
2839                 final Node test = caseNode.getTest();
2840 
2841                 if (test != null) {
2842                     final Integer value = (Integer)((LiteralNode<?>)test).getValue();
2843                     final Label   entry = caseNode.getEntry();
2844 
2845                     // Take first duplicate.
2846                     if (!tree.containsKey(value)) {
2847                         tree.put(value, entry);
2848                     }
2849                 }
2850             }
2851 
2852             // Copy values and labels to arrays.
2853             final int       size   = tree.size();
2854             final Integer[] values = tree.keySet().toArray(new Integer[size]);
2855             final Label[]   labels = tree.values().toArray(new Label[size]);
2856 
2857             // Discern low, high and range.
2858             final int lo    = values[0];
2859             final int hi    = values[size - 1];
2860             final long range = (long)hi - (long)lo + 1;
2861 
2862             // Find an unused value for default.
2863             int deflt = Integer.MIN_VALUE;
2864             for (final int value : values) {
2865                 if (deflt == value) {
2866                     deflt++;
2867                 } else if (deflt < value) {
2868                     break;
2869                 }
2870             }
2871 
2872             // Load switch expression.
2873             loadExpressionUnbounded(expression);
2874             final Type type = expression.getType();
2875 
2876             // If expression not int see if we can convert, if not use deflt to trigger default.
2877             if (!type.isInteger()) {
2878                 method.load(deflt);
2879                 final Class<?> exprClass = type.getTypeClass();
2880                 method.invoke(staticCallNoLookup(ScriptRuntime.class, "switchTagAsInt", int.class, exprClass.isPrimitive()? exprClass : Object.class, int.class));
2881             }
2882 
2883             if(hasSkipConversion) {
2884                 assert defaultLabel == breakLabel;
2885                 defaultLabel = new Label("switch_skip");
2886             }
2887             // TABLESWITCH needs (range + 3) 32-bit values; LOOKUPSWITCH needs ((size * 2) + 2). Choose the one with
2888             // smaller representation, favor TABLESWITCH when they're equal size.
2889             if (range + 1 <= (size * 2) && range <= Integer.MAX_VALUE) {
2890                 final Label[] table = new Label[(int)range];
2891                 Arrays.fill(table, defaultLabel);
2892                 for (int i = 0; i < size; i++) {
2893                     final int value = values[i];
2894                     table[value - lo] = labels[i];
2895                 }
2896 
2897                 method.tableswitch(lo, hi, defaultLabel, table);
2898             } else {
2899                 final int[] ints = new int[size];
2900                 for (int i = 0; i < size; i++) {
2901                     ints[i] = values[i];
2902                 }
2903 
2904                 method.lookupswitch(defaultLabel, ints, labels);
2905             }
2906             // This is a synthetic "default case" used in absence of actual default case, created if we need to apply
2907             // local variable conversions if neither case is taken.
2908             if(hasSkipConversion) {
2909                 method.label(defaultLabel);
2910                 method.beforeJoinPoint(switchNode);
2911                 method._goto(breakLabel);
2912             }
2913         } else {
2914             final Symbol tagSymbol = switchNode.getTag();
2915             // TODO: we could have non-object tag
2916             final int tagSlot = tagSymbol.getSlot(Type.OBJECT);
2917             loadExpressionAsObject(expression);
2918             method.store(tagSymbol, Type.OBJECT);
2919 
2920             for (final CaseNode caseNode : cases) {
2921                 final Expression test = caseNode.getTest();
2922 
2923                 if (test != null) {
2924                     method.load(Type.OBJECT, tagSlot);
2925                     loadExpressionAsObject(test);
2926                     method.invoke(ScriptRuntime.EQ_STRICT);
2927                     method.ifne(caseNode.getEntry());
2928                 }
2929             }
2930 
2931             if (defaultCase != null) {
2932                 method._goto(defaultLabel);
2933             } else {
2934                 method.beforeJoinPoint(switchNode);
2935                 method._goto(breakLabel);
2936             }
2937         }
2938 
2939         // First case is only reachable through jump
2940         assert !method.isReachable();
2941 
2942         for (final CaseNode caseNode : cases) {
2943             final Label fallThroughLabel;
2944             if(caseNode.getLocalVariableConversion() != null && method.isReachable()) {
2945                 fallThroughLabel = new Label("fallthrough");
2946                 method._goto(fallThroughLabel);
2947             } else {
2948                 fallThroughLabel = null;
2949             }
2950             method.label(caseNode.getEntry());
2951             method.beforeJoinPoint(caseNode);
2952             if(fallThroughLabel != null) {
2953                 method.label(fallThroughLabel);
2954             }
2955             caseNode.getBody().accept(this);
2956         }
2957 
2958         method.breakLabel(breakLabel, liveLocalsOnBreak);
2959 
2960         return false;
2961     }
2962 
2963     @Override
2964     public boolean enterThrowNode(final ThrowNode throwNode) {
2965         if(!method.isReachable()) {
2966             return false;
2967         }
2968         enterStatement(throwNode);
2969 
2970         if (throwNode.isSyntheticRethrow()) {
2971             method.beforeJoinPoint(throwNode);
2972 
2973             //do not wrap whatever this is in an ecma exception, just rethrow it
2974             final IdentNode exceptionExpr = (IdentNode)throwNode.getExpression();
2975             final Symbol exceptionSymbol = exceptionExpr.getSymbol();
2976             method.load(exceptionSymbol, EXCEPTION_TYPE);
2977             method.checkcast(EXCEPTION_TYPE.getTypeClass());
2978             method.athrow();
2979             return false;
2980         }
2981 
2982         final Source     source     = getCurrentSource();
2983         final Expression expression = throwNode.getExpression();
2984         final int        position   = throwNode.position();
2985         final int        line       = throwNode.getLineNumber();
2986         final int        column     = source.getColumn(position);
2987 
2988         // NOTE: we first evaluate the expression, and only after it was evaluated do we create the new ECMAException
2989         // object and then somewhat cumbersomely move it beneath the evaluated expression on the stack. The reason for
2990         // this is that if expression is optimistic (or contains an optimistic subexpression), we'd potentially access
2991         // the not-yet-<init>ialized object on the stack from the UnwarrantedOptimismException handler, and bytecode
2992         // verifier forbids that.
2993         loadExpressionAsObject(expression);
2994 
2995         method.load(source.getName());
2996         method.load(line);
2997         method.load(column);
2998         method.invoke(ECMAException.CREATE);
2999 
3000         method.beforeJoinPoint(throwNode);
3001         method.athrow();
3002 
3003         return false;
3004     }
3005 
3006     private Source getCurrentSource() {
3007         return lc.getCurrentFunction().getSource();
3008     }
3009 
3010     @Override
3011     public boolean enterTryNode(final TryNode tryNode) {
3012         if(!method.isReachable()) {
3013             return false;
3014         }
3015         enterStatement(tryNode);
3016 
3017         final Block       body        = tryNode.getBody();
3018         final List<Block> catchBlocks = tryNode.getCatchBlocks();
3019         final Symbol      vmException = tryNode.getException();
3020         final Label       entry       = new Label("try");
3021         final Label       recovery    = new Label("catch");
3022         final Label       exit        = new Label("end_try");
3023         final Label       skip        = new Label("skip");
3024 
3025         method.canThrow(recovery);
3026         // Effect any conversions that might be observed at the entry of the catch node before entering the try node.
3027         // This is because even the first instruction in the try block must be presumed to be able to transfer control
3028         // to the catch block. Note that this doesn't kill the original values; in this regard it works a lot like
3029         // conversions of assignments within the try block.
3030         method.beforeTry(tryNode, recovery);
3031         method.label(entry);
3032         catchLabels.push(recovery);
3033         try {
3034             body.accept(this);
3035         } finally {
3036             assert catchLabels.peek() == recovery;
3037             catchLabels.pop();
3038         }
3039 
3040         method.label(exit);
3041         final boolean bodyCanThrow = exit.isAfter(entry);
3042         if(!bodyCanThrow) {
3043             // The body can't throw an exception; don't even bother emitting the catch handlers, they're all dead code.
3044             return false;
3045         }
3046 
3047         method._try(entry, exit, recovery, Throwable.class);
3048 
3049         if (method.isReachable()) {
3050             method._goto(skip);
3051         }
3052         method._catch(recovery);
3053         method.store(vmException, EXCEPTION_TYPE);
3054 
3055         final int catchBlockCount = catchBlocks.size();
3056         final Label afterCatch = new Label("after_catch");
3057         for (int i = 0; i < catchBlockCount; i++) {
3058             assert method.isReachable();
3059             final Block catchBlock = catchBlocks.get(i);
3060 
3061             // Because of the peculiarities of the flow control, we need to use an explicit push/enterBlock/leaveBlock
3062             // here.
3063             lc.push(catchBlock);
3064             enterBlock(catchBlock);
3065 
3066             final CatchNode  catchNode          = (CatchNode)catchBlocks.get(i).getStatements().get(0);
3067             final IdentNode  exception          = catchNode.getException();
3068             final Expression exceptionCondition = catchNode.getExceptionCondition();
3069             final Block      catchBody          = catchNode.getBody();
3070 
3071             new Store<IdentNode>(exception) {
3072                 @Override
3073                 protected void storeNonDiscard() {
3074                     // This expression is neither part of a discard, nor needs to be left on the stack after it was
3075                     // stored, so we override storeNonDiscard to be a no-op.
3076                 }
3077 
3078                 @Override
3079                 protected void evaluate() {
3080                     if (catchNode.isSyntheticRethrow()) {
3081                         method.load(vmException, EXCEPTION_TYPE);
3082                         return;
3083                     }
3084                     /*
3085                      * If caught object is an instance of ECMAException, then
3086                      * bind obj.thrown to the script catch var. Or else bind the
3087                      * caught object itself to the script catch var.
3088                      */
3089                     final Label notEcmaException = new Label("no_ecma_exception");
3090                     method.load(vmException, EXCEPTION_TYPE).dup()._instanceof(ECMAException.class).ifeq(notEcmaException);
3091                     method.checkcast(ECMAException.class); //TODO is this necessary?
3092                     method.getField(ECMAException.THROWN);
3093                     method.label(notEcmaException);
3094                 }
3095             }.store();
3096 
3097             final boolean isConditionalCatch = exceptionCondition != null;
3098             final Label nextCatch;
3099             if (isConditionalCatch) {
3100                 loadExpressionAsBoolean(exceptionCondition);
3101                 nextCatch = new Label("next_catch");
3102                 nextCatch.markAsBreakTarget();
3103                 method.ifeq(nextCatch);
3104             } else {
3105                 nextCatch = null;
3106             }
3107 
3108             catchBody.accept(this);
3109             leaveBlock(catchBlock);
3110             lc.pop(catchBlock);
3111             if(method.isReachable()) {
3112                 method._goto(afterCatch);
3113             }
3114             if(nextCatch != null) {
3115                 method.breakLabel(nextCatch, lc.getUsedSlotCount());
3116             }
3117         }
3118 
3119         assert !method.isReachable();
3120         // afterCatch could be the same as skip, except that we need to establish that the vmException is dead.
3121         method.label(afterCatch);
3122         if(method.isReachable()) {
3123             method.markDeadLocalVariable(vmException);
3124         }
3125         method.label(skip);
3126 
3127         // Finally body is always inlined elsewhere so it doesn't need to be emitted
3128         return false;
3129     }
3130 
3131     @Override
3132     public boolean enterVarNode(final VarNode varNode) {
3133         if(!method.isReachable()) {
3134             return false;
3135         }
3136         final Expression init = varNode.getInit();
3137         final IdentNode identNode = varNode.getName();
3138         final Symbol identSymbol = identNode.getSymbol();
3139         assert identSymbol != null : "variable node " + varNode + " requires a name with a symbol";
3140         final boolean needsScope = identSymbol.isScope();
3141 
3142         if (init == null) {
3143             if (needsScope && varNode.isBlockScoped()) {
3144                 // block scoped variables need a DECLARE flag to signal end of temporal dead zone (TDZ)
3145                 method.loadCompilerConstant(SCOPE);
3146                 method.loadUndefined(Type.OBJECT);
3147                 final int flags = CALLSITE_SCOPE | getCallSiteFlags() | (varNode.isBlockScoped() ? CALLSITE_DECLARE : 0);
3148                 assert isFastScope(identSymbol);
3149                 storeFastScopeVar(identSymbol, flags);
3150             }
3151             return false;
3152         }
3153 
3154         enterStatement(varNode);
3155         assert method != null;
3156 
3157         if (needsScope) {
3158             method.loadCompilerConstant(SCOPE);
3159         }
3160 
3161         if (needsScope) {
3162             loadExpressionUnbounded(init);
3163             // block scoped variables need a DECLARE flag to signal end of temporal dead zone (TDZ)
3164             final int flags = CALLSITE_SCOPE | getCallSiteFlags() | (varNode.isBlockScoped() ? CALLSITE_DECLARE : 0);
3165             if (isFastScope(identSymbol)) {
3166                 storeFastScopeVar(identSymbol, flags);
3167             } else {
3168                 method.dynamicSet(identNode.getName(), flags, false);
3169             }
3170         } else {
3171             final Type identType = identNode.getType();
3172             if(identType == Type.UNDEFINED) {
3173                 // The initializer is either itself undefined (explicit assignment of undefined to undefined),
3174                 // or the left hand side is a dead variable.
3175                 assert init.getType() == Type.UNDEFINED || identNode.getSymbol().slotCount() == 0;
3176                 loadAndDiscard(init);
3177                 return false;
3178             }
3179             loadExpressionAsType(init, identType);
3180             storeIdentWithCatchConversion(identNode, identType);
3181         }
3182 
3183         return false;
3184     }
3185 
3186     private void storeIdentWithCatchConversion(final IdentNode identNode, final Type type) {
3187         // Assignments happening in try/catch blocks need to ensure that they also store a possibly wider typed value
3188         // that will be live at the exit from the try block
3189         final LocalVariableConversion conversion = identNode.getLocalVariableConversion();
3190         final Symbol symbol = identNode.getSymbol();
3191         if(conversion != null && conversion.isLive()) {
3192             assert symbol == conversion.getSymbol();
3193             assert symbol.isBytecodeLocal();
3194             // Only a single conversion from the target type to the join type is expected.
3195             assert conversion.getNext() == null;
3196             assert conversion.getFrom() == type;
3197             // We must propagate potential type change to the catch block
3198             final Label catchLabel = catchLabels.peek();
3199             assert catchLabel != METHOD_BOUNDARY; // ident conversion only exists in try blocks
3200             assert catchLabel.isReachable();
3201             final Type joinType = conversion.getTo();
3202             final Label.Stack catchStack = catchLabel.getStack();
3203             final int joinSlot = symbol.getSlot(joinType);
3204             // With nested try/catch blocks (incl. synthetic ones for finally), we can have a supposed conversion for
3205             // the exception symbol in the nested catch, but it isn't live in the outer catch block, so prevent doing
3206             // conversions for it. E.g. in "try { try { ... } catch(e) { e = 1; } } catch(e2) { ... }", we must not
3207             // introduce an I->O conversion on "e = 1" assignment as "e" is not live in "catch(e2)".
3208             if(catchStack.getUsedSlotsWithLiveTemporaries() > joinSlot) {
3209                 method.dup();
3210                 method.convert(joinType);
3211                 method.store(symbol, joinType);
3212                 catchLabel.getStack().onLocalStore(joinType, joinSlot, true);
3213                 method.canThrow(catchLabel);
3214                 // Store but keep the previous store live too.
3215                 method.store(symbol, type, false);
3216                 return;
3217             }
3218         }
3219 
3220         method.store(symbol, type, true);
3221     }
3222 
3223     @Override
3224     public boolean enterWhileNode(final WhileNode whileNode) {
3225         if(!method.isReachable()) {
3226             return false;
3227         }
3228         if(whileNode.isDoWhile()) {
3229             enterDoWhile(whileNode);
3230         } else {
3231             enterStatement(whileNode);
3232             enterForOrWhile(whileNode, null);
3233         }
3234         return false;
3235     }
3236 
3237     private void enterForOrWhile(final LoopNode loopNode, final JoinPredecessorExpression modify) {
3238         // NOTE: the usual pattern for compiling test-first loops is "GOTO test; body; test; IFNE body". We use the less
3239         // conventional "test; IFEQ break; body; GOTO test; break;". It has one extra unconditional GOTO in each repeat
3240         // of the loop, but it's not a problem for modern JIT compilers. We do this because our local variable type
3241         // tracking is unfortunately not really prepared for out-of-order execution, e.g. compiling the following
3242         // contrived but legal JavaScript code snippet would fail because the test changes the type of "i" from object
3243         // to double: var i = {valueOf: function() { return 1} }; while(--i >= 0) { ... }
3244         // Instead of adding more complexity to the local variable type tracking, we instead choose to emit this
3245         // different code shape.
3246         final int liveLocalsOnBreak = method.getUsedSlotsWithLiveTemporaries();
3247         final JoinPredecessorExpression test = loopNode.getTest();
3248         if(Expression.isAlwaysFalse(test)) {
3249             loadAndDiscard(test);
3250             return;
3251         }
3252 
3253         method.beforeJoinPoint(loopNode);
3254 
3255         final Label continueLabel = loopNode.getContinueLabel();
3256         final Label repeatLabel = modify != null ? new Label("for_repeat") : continueLabel;
3257         method.label(repeatLabel);
3258         final int liveLocalsOnContinue = method.getUsedSlotsWithLiveTemporaries();
3259 
3260         final Block   body                  = loopNode.getBody();
3261         final Label   breakLabel            = loopNode.getBreakLabel();
3262         final boolean testHasLiveConversion = test != null && LocalVariableConversion.hasLiveConversion(test);
3263 
3264         if(Expression.isAlwaysTrue(test)) {
3265             if(test != null) {
3266                 loadAndDiscard(test);
3267                 if(testHasLiveConversion) {
3268                     method.beforeJoinPoint(test);
3269                 }
3270             }
3271         } else if (test != null) {
3272             if (testHasLiveConversion) {
3273                 emitBranch(test.getExpression(), body.getEntryLabel(), true);
3274                 method.beforeJoinPoint(test);
3275                 method._goto(breakLabel);
3276             } else {
3277                 emitBranch(test.getExpression(), breakLabel, false);
3278             }
3279         }
3280 
3281         body.accept(this);
3282         if(repeatLabel != continueLabel) {
3283             emitContinueLabel(continueLabel, liveLocalsOnContinue);
3284         }
3285 
3286         if (loopNode.hasPerIterationScope() && lc.getCurrentBlock().needsScope()) {
3287             // ES6 for loops with LET init need a new scope for each iteration. We just create a shallow copy here.
3288             method.loadCompilerConstant(SCOPE);
3289             method.invoke(virtualCallNoLookup(ScriptObject.class, "copy", ScriptObject.class));
3290             method.storeCompilerConstant(SCOPE);
3291         }
3292 
3293         if(method.isReachable()) {
3294             if(modify != null) {
3295                 lineNumber(loopNode);
3296                 loadAndDiscard(modify);
3297                 method.beforeJoinPoint(modify);
3298             }
3299             method._goto(repeatLabel);
3300         }
3301 
3302         method.breakLabel(breakLabel, liveLocalsOnBreak);
3303     }
3304 
3305     private void emitContinueLabel(final Label continueLabel, final int liveLocals) {
3306         final boolean reachable = method.isReachable();
3307         method.breakLabel(continueLabel, liveLocals);
3308         // If we reach here only through a continue statement (e.g. body does not exit normally) then the
3309         // continueLabel can have extra non-temp symbols (e.g. exception from a try/catch contained in the body). We
3310         // must make sure those are thrown away.
3311         if(!reachable) {
3312             method.undefineLocalVariables(lc.getUsedSlotCount(), false);
3313         }
3314     }
3315 
3316     private void enterDoWhile(final WhileNode whileNode) {
3317         final int liveLocalsOnContinueOrBreak = method.getUsedSlotsWithLiveTemporaries();
3318         method.beforeJoinPoint(whileNode);
3319 
3320         final Block body = whileNode.getBody();
3321         body.accept(this);
3322 
3323         emitContinueLabel(whileNode.getContinueLabel(), liveLocalsOnContinueOrBreak);
3324         if(method.isReachable()) {
3325             lineNumber(whileNode);
3326             final JoinPredecessorExpression test = whileNode.getTest();
3327             final Label bodyEntryLabel = body.getEntryLabel();
3328             final boolean testHasLiveConversion = LocalVariableConversion.hasLiveConversion(test);
3329             if(Expression.isAlwaysFalse(test)) {
3330                 loadAndDiscard(test);
3331                 if(testHasLiveConversion) {
3332                     method.beforeJoinPoint(test);
3333                 }
3334             } else if(testHasLiveConversion) {
3335                 // If we have conversions after the test in do-while, they need to be effected on both branches.
3336                 final Label beforeExit = new Label("do_while_preexit");
3337                 emitBranch(test.getExpression(), beforeExit, false);
3338                 method.beforeJoinPoint(test);
3339                 method._goto(bodyEntryLabel);
3340                 method.label(beforeExit);
3341                 method.beforeJoinPoint(test);
3342             } else {
3343                 emitBranch(test.getExpression(), bodyEntryLabel, true);
3344             }
3345         }
3346         method.breakLabel(whileNode.getBreakLabel(), liveLocalsOnContinueOrBreak);
3347     }
3348 
3349 
3350     @Override
3351     public boolean enterWithNode(final WithNode withNode) {
3352         if(!method.isReachable()) {
3353             return false;
3354         }
3355         enterStatement(withNode);
3356         final Expression expression = withNode.getExpression();
3357         final Block      body       = withNode.getBody();
3358 
3359         // It is possible to have a "pathological" case where the with block does not reference *any* identifiers. It's
3360         // pointless, but legal. In that case, if nothing else in the method forced the assignment of a slot to the
3361         // scope object, its' possible that it won't have a slot assigned. In this case we'll only evaluate expression
3362         // for its side effect and visit the body, and not bother opening and closing a WithObject.
3363         final boolean hasScope = method.hasScope();
3364 
3365         if (hasScope) {
3366             method.loadCompilerConstant(SCOPE);
3367         }
3368 
3369         loadExpressionAsObject(expression);
3370 
3371         final Label tryLabel;
3372         if (hasScope) {
3373             // Construct a WithObject if we have a scope
3374             method.invoke(ScriptRuntime.OPEN_WITH);
3375             method.storeCompilerConstant(SCOPE);
3376             tryLabel = new Label("with_try");
3377             method.label(tryLabel);
3378         } else {
3379             // We just loaded the expression for its side effect and to check
3380             // for null or undefined value.
3381             globalCheckObjectCoercible();
3382             tryLabel = null;
3383         }
3384 
3385         // Always process body
3386         body.accept(this);
3387 
3388         if (hasScope) {
3389             // Ensure we always close the WithObject
3390             final Label endLabel   = new Label("with_end");
3391             final Label catchLabel = new Label("with_catch");
3392             final Label exitLabel  = new Label("with_exit");
3393 
3394             method.label(endLabel);
3395             // Somewhat conservatively presume that if the body is not empty, it can throw an exception. In any case,
3396             // we must prevent trying to emit a try-catch for empty range, as it causes a verification error.
3397             final boolean bodyCanThrow = endLabel.isAfter(tryLabel);
3398             if(bodyCanThrow) {
3399                 method._try(tryLabel, endLabel, catchLabel);
3400             }
3401 
3402             final boolean reachable = method.isReachable();
3403             if(reachable) {
3404                 popScope();
3405                 if(bodyCanThrow) {
3406                     method._goto(exitLabel);
3407                 }
3408             }
3409 
3410             if(bodyCanThrow) {
3411                 method._catch(catchLabel);
3412                 popScopeException();
3413                 method.athrow();
3414                 if(reachable) {
3415                     method.label(exitLabel);
3416                 }
3417             }
3418         }
3419         return false;
3420     }
3421 
3422     private void loadADD(final UnaryNode unaryNode, final TypeBounds resultBounds) {
3423         loadExpression(unaryNode.getExpression(), resultBounds.booleanToInt().notWiderThan(Type.NUMBER));
3424         if(method.peekType() == Type.BOOLEAN) {
3425             // It's a no-op in bytecode, but we must make sure it is treated as an int for purposes of type signatures
3426             method.convert(Type.INT);
3427         }
3428     }
3429 
3430     private void loadBIT_NOT(final UnaryNode unaryNode) {
3431         loadExpression(unaryNode.getExpression(), TypeBounds.INT).load(-1).xor();
3432     }
3433 
3434     private void loadDECINC(final UnaryNode unaryNode) {
3435         final Expression operand     = unaryNode.getExpression();
3436         final Type       type        = unaryNode.getType();
3437         final TypeBounds typeBounds  = new TypeBounds(type, Type.NUMBER);
3438         final TokenType  tokenType   = unaryNode.tokenType();
3439         final boolean    isPostfix   = tokenType == TokenType.DECPOSTFIX || tokenType == TokenType.INCPOSTFIX;
3440         final boolean    isIncrement = tokenType == TokenType.INCPREFIX || tokenType == TokenType.INCPOSTFIX;
3441 
3442         assert !type.isObject();
3443 
3444         new SelfModifyingStore<UnaryNode>(unaryNode, operand) {
3445 
3446             private void loadRhs() {
3447                 loadExpression(operand, typeBounds, true);
3448             }
3449 
3450             @Override
3451             protected void evaluate() {
3452                 if(isPostfix) {
3453                     loadRhs();
3454                 } else {
3455                     new OptimisticOperation(unaryNode, typeBounds) {
3456                         @Override
3457                         void loadStack() {
3458                             loadRhs();
3459                             loadMinusOne();
3460                         }
3461                         @Override
3462                         void consumeStack() {
3463                             doDecInc(getProgramPoint());
3464                         }
3465                     }.emit(getOptimisticIgnoreCountForSelfModifyingExpression(operand));
3466                 }
3467             }
3468 
3469             @Override
3470             protected void storeNonDiscard() {
3471                 super.storeNonDiscard();
3472                 if (isPostfix) {
3473                     new OptimisticOperation(unaryNode, typeBounds) {
3474                         @Override
3475                         void loadStack() {
3476                             loadMinusOne();
3477                         }
3478                         @Override
3479                         void consumeStack() {
3480                             doDecInc(getProgramPoint());
3481                         }
3482                     }.emit(1); // 1 for non-incremented result on the top of the stack pushed in evaluate()
3483                 }
3484             }
3485 
3486             private void loadMinusOne() {
3487                 if (type.isInteger()) {
3488                     method.load(isIncrement ? 1 : -1);
3489                 } else if (type.isLong()) {
3490                     method.load(isIncrement ? 1L : -1L);
3491                 } else {
3492                     method.load(isIncrement ? 1.0 : -1.0);
3493                 }
3494             }
3495 
3496             private void doDecInc(final int programPoint) {
3497                 method.add(programPoint);
3498             }
3499         }.store();
3500     }
3501 
3502     private static int getOptimisticIgnoreCountForSelfModifyingExpression(final Expression target) {
3503         return target instanceof AccessNode ? 1 : target instanceof IndexNode ? 2 : 0;
3504     }
3505 
3506     private void loadAndDiscard(final Expression expr) {
3507         // TODO: move checks for discarding to actual expression load code (e.g. as we do with void). That way we might
3508         // be able to eliminate even more checks.
3509         if(expr instanceof PrimitiveLiteralNode | isLocalVariable(expr)) {
3510             assert lc.getCurrentDiscard() != expr;
3511             // Don't bother evaluating expressions without side effects. Typical usage is "void 0" for reliably generating
3512             // undefined.
3513             return;
3514         }
3515 
3516         lc.pushDiscard(expr);
3517         loadExpression(expr, TypeBounds.UNBOUNDED);
3518         if (lc.getCurrentDiscard() == expr) {
3519             assert !expr.isAssignment();
3520             // NOTE: if we had a way to load with type void, we could avoid popping
3521             method.pop();
3522             lc.popDiscard();
3523         }
3524     }
3525 
3526     private void loadNEW(final UnaryNode unaryNode) {
3527         final CallNode callNode = (CallNode)unaryNode.getExpression();
3528         final List<Expression> args   = callNode.getArgs();
3529 
3530         // Load function reference.
3531         loadExpressionAsObject(callNode.getFunction()); // must detect type error
3532 
3533         method.dynamicNew(1 + loadArgs(args), getCallSiteFlags());
3534     }
3535 
3536     private void loadNOT(final UnaryNode unaryNode) {
3537         final Expression expr = unaryNode.getExpression();
3538         if(expr instanceof UnaryNode && expr.isTokenType(TokenType.NOT)) {
3539             // !!x is idiomatic boolean cast in JavaScript
3540             loadExpressionAsBoolean(((UnaryNode)expr).getExpression());
3541         } else {
3542             final Label trueLabel  = new Label("true");
3543             final Label afterLabel = new Label("after");
3544 
3545             emitBranch(expr, trueLabel, true);
3546             method.load(true);
3547             method._goto(afterLabel);
3548             method.label(trueLabel);
3549             method.load(false);
3550             method.label(afterLabel);
3551         }
3552     }
3553 
3554     private void loadSUB(final UnaryNode unaryNode, final TypeBounds resultBounds) {
3555         final Type type = unaryNode.getType();
3556         assert type.isNumeric();
3557         final TypeBounds numericBounds = resultBounds.booleanToInt();
3558         new OptimisticOperation(unaryNode, numericBounds) {
3559             @Override
3560             void loadStack() {
3561                 final Expression expr = unaryNode.getExpression();
3562                 loadExpression(expr, numericBounds.notWiderThan(Type.NUMBER));
3563             }
3564             @Override
3565             void consumeStack() {
3566                 // Must do an explicit conversion to the operation's type when it's double so that we correctly handle
3567                 // negation of an int 0 to a double -0. With this, we get the correct negation of a local variable after
3568                 // it deoptimized, e.g. "iload_2; i2d; dneg". Without this, we get "iload_2; ineg; i2d".
3569                 if(type.isNumber()) {
3570                     method.convert(type);
3571                 }
3572                 method.neg(getProgramPoint());
3573             }
3574         }.emit();
3575     }
3576 
3577     public void loadVOID(final UnaryNode unaryNode, final TypeBounds resultBounds) {
3578         loadAndDiscard(unaryNode.getExpression());
3579         if(lc.getCurrentDiscard() == unaryNode) {
3580             lc.popDiscard();
3581         } else {
3582             method.loadUndefined(resultBounds.widest);
3583         }
3584     }
3585 
3586     public void loadADD(final BinaryNode binaryNode, final TypeBounds resultBounds) {
3587         new OptimisticOperation(binaryNode, resultBounds) {
3588             @Override
3589             void loadStack() {
3590                 final TypeBounds operandBounds;
3591                 final boolean isOptimistic = isValid(getProgramPoint());
3592                 boolean forceConversionSeparation = false;
3593                 if(isOptimistic) {
3594                     operandBounds = new TypeBounds(binaryNode.getType(), Type.OBJECT);
3595                 } else {
3596                     // Non-optimistic, non-FP +. Allow it to overflow.
3597                     final Type widestOperationType = binaryNode.getWidestOperationType();
3598                     operandBounds = new TypeBounds(Type.narrowest(binaryNode.getWidestOperandType(), resultBounds.widest), widestOperationType);
3599                     forceConversionSeparation = widestOperationType.narrowerThan(resultBounds.widest);
3600                 }
3601                 loadBinaryOperands(binaryNode.lhs(), binaryNode.rhs(), operandBounds, false, forceConversionSeparation);
3602             }
3603 
3604             @Override
3605             void consumeStack() {
3606                 method.add(getProgramPoint());
3607             }
3608         }.emit();
3609     }
3610 
3611     private void loadAND_OR(final BinaryNode binaryNode, final TypeBounds resultBounds, final boolean isAnd) {
3612         final Type narrowestOperandType = Type.widestReturnType(binaryNode.lhs().getType(), binaryNode.rhs().getType());
3613 
3614         final Label skip = new Label("skip");
3615         if(narrowestOperandType == Type.BOOLEAN) {
3616             // optimize all-boolean logical expressions
3617             final Label onTrue = new Label("andor_true");
3618             emitBranch(binaryNode, onTrue, true);
3619             method.load(false);
3620             method._goto(skip);
3621             method.label(onTrue);
3622             method.load(true);
3623             method.label(skip);
3624             return;
3625         }
3626 
3627         final TypeBounds outBounds = resultBounds.notNarrowerThan(narrowestOperandType);
3628         final JoinPredecessorExpression lhs = (JoinPredecessorExpression)binaryNode.lhs();
3629         final boolean lhsConvert = LocalVariableConversion.hasLiveConversion(lhs);
3630         final Label evalRhs = lhsConvert ? new Label("eval_rhs") : null;
3631 
3632         loadExpression(lhs, outBounds).dup().convert(Type.BOOLEAN);
3633         if (isAnd) {
3634             if(lhsConvert) {
3635                 method.ifne(evalRhs);
3636             } else {
3637                 method.ifeq(skip);
3638             }
3639         } else if(lhsConvert) {
3640             method.ifeq(evalRhs);
3641         } else {
3642             method.ifne(skip);
3643         }
3644 
3645         if(lhsConvert) {
3646             method.beforeJoinPoint(lhs);
3647             method._goto(skip);
3648             method.label(evalRhs);
3649         }
3650 
3651         method.pop();
3652         final JoinPredecessorExpression rhs = (JoinPredecessorExpression)binaryNode.rhs();
3653         loadExpression(rhs, outBounds);
3654         method.beforeJoinPoint(rhs);
3655         method.label(skip);
3656     }
3657 
3658     private static boolean isLocalVariable(final Expression lhs) {
3659         return lhs instanceof IdentNode && isLocalVariable((IdentNode)lhs);
3660     }
3661 
3662     private static boolean isLocalVariable(final IdentNode lhs) {
3663         return lhs.getSymbol().isBytecodeLocal();
3664     }
3665 
3666     // NOTE: does not use resultBounds as the assignment is driven by the type of the RHS
3667     private void loadASSIGN(final BinaryNode binaryNode) {
3668         final Expression lhs = binaryNode.lhs();
3669         final Expression rhs = binaryNode.rhs();
3670 
3671         final Type rhsType = rhs.getType();
3672         // Detect dead assignments
3673         if(lhs instanceof IdentNode) {
3674             final Symbol symbol = ((IdentNode)lhs).getSymbol();
3675             if(!symbol.isScope() && !symbol.hasSlotFor(rhsType) && lc.getCurrentDiscard() == binaryNode) {
3676                 loadAndDiscard(rhs);
3677                 lc.popDiscard();
3678                 method.markDeadLocalVariable(symbol);
3679                 return;
3680             }
3681         }
3682 
3683         new Store<BinaryNode>(binaryNode, lhs) {
3684             @Override
3685             protected void evaluate() {
3686                 // NOTE: we're loading with "at least as wide as" so optimistic operations on the right hand side
3687                 // remain optimistic, and then explicitly convert to the required type if needed.
3688                 loadExpressionAsType(rhs, rhsType);
3689             }
3690         }.store();
3691     }
3692 
3693     /**
3694      * Binary self-assignment that can be optimistic: +=, -=, *=, and /=.
3695      */
3696     private abstract class BinaryOptimisticSelfAssignment extends SelfModifyingStore<BinaryNode> {
3697 
3698         /**
3699          * Constructor
3700          *
3701          * @param node the assign op node
3702          */
3703         BinaryOptimisticSelfAssignment(final BinaryNode node) {
3704             super(node, node.lhs());
3705         }
3706 
3707         protected abstract void op(OptimisticOperation oo);
3708 
3709         @Override
3710         protected void evaluate() {
3711             final Expression lhs = assignNode.lhs();
3712             final Expression rhs = assignNode.rhs();
3713             final Type widestOperationType = assignNode.getWidestOperationType();
3714             final TypeBounds bounds = new TypeBounds(assignNode.getType(), widestOperationType);
3715             new OptimisticOperation(assignNode, bounds) {
3716                 @Override
3717                 void loadStack() {
3718                     final boolean forceConversionSeparation;
3719                     if (isValid(getProgramPoint()) || widestOperationType == Type.NUMBER) {
3720                         forceConversionSeparation = false;
3721                     } else {
3722                         final Type operandType = Type.widest(booleanToInt(objectToNumber(lhs.getType())), booleanToInt(objectToNumber(rhs.getType())));
3723                         forceConversionSeparation = operandType.narrowerThan(widestOperationType);
3724                     }
3725                     loadBinaryOperands(lhs, rhs, bounds, true, forceConversionSeparation);
3726                 }
3727                 @Override
3728                 void consumeStack() {
3729                     op(this);
3730                 }
3731             }.emit(getOptimisticIgnoreCountForSelfModifyingExpression(lhs));
3732             method.convert(assignNode.getType());
3733         }
3734     }
3735 
3736     /**
3737      * Non-optimistic binary self-assignment operation. Basically, everything except +=, -=, *=, and /=.
3738      */
3739     private abstract class BinarySelfAssignment extends SelfModifyingStore<BinaryNode> {
3740         BinarySelfAssignment(final BinaryNode node) {
3741             super(node, node.lhs());
3742         }
3743 
3744         protected abstract void op();
3745 
3746         @Override
3747         protected void evaluate() {
3748             loadBinaryOperands(assignNode.lhs(), assignNode.rhs(), TypeBounds.UNBOUNDED.notWiderThan(assignNode.getWidestOperandType()), true, false);
3749             op();
3750         }
3751     }
3752 
3753     private void loadASSIGN_ADD(final BinaryNode binaryNode) {
3754         new BinaryOptimisticSelfAssignment(binaryNode) {
3755             @Override
3756             protected void op(final OptimisticOperation oo) {
3757                 assert !(binaryNode.getType().isObject() && oo.isOptimistic);
3758                 method.add(oo.getProgramPoint());
3759             }
3760         }.store();
3761     }
3762 
3763     private void loadASSIGN_BIT_AND(final BinaryNode binaryNode) {
3764         new BinarySelfAssignment(binaryNode) {
3765             @Override
3766             protected void op() {
3767                 method.and();
3768             }
3769         }.store();
3770     }
3771 
3772     private void loadASSIGN_BIT_OR(final BinaryNode binaryNode) {
3773         new BinarySelfAssignment(binaryNode) {
3774             @Override
3775             protected void op() {
3776                 method.or();
3777             }
3778         }.store();
3779     }
3780 
3781     private void loadASSIGN_BIT_XOR(final BinaryNode binaryNode) {
3782         new BinarySelfAssignment(binaryNode) {
3783             @Override
3784             protected void op() {
3785                 method.xor();
3786             }
3787         }.store();
3788     }
3789 
3790     private void loadASSIGN_DIV(final BinaryNode binaryNode) {
3791         new BinaryOptimisticSelfAssignment(binaryNode) {
3792             @Override
3793             protected void op(final OptimisticOperation oo) {
3794                 method.div(oo.getProgramPoint());
3795             }
3796         }.store();
3797     }
3798 
3799     private void loadASSIGN_MOD(final BinaryNode binaryNode) {
3800         new BinaryOptimisticSelfAssignment(binaryNode) {
3801             @Override
3802             protected void op(final OptimisticOperation oo) {
3803                 method.rem(oo.getProgramPoint());
3804             }
3805         }.store();
3806     }
3807 
3808     private void loadASSIGN_MUL(final BinaryNode binaryNode) {
3809         new BinaryOptimisticSelfAssignment(binaryNode) {
3810             @Override
3811             protected void op(final OptimisticOperation oo) {
3812                 method.mul(oo.getProgramPoint());
3813             }
3814         }.store();
3815     }
3816 
3817     private void loadASSIGN_SAR(final BinaryNode binaryNode) {
3818         new BinarySelfAssignment(binaryNode) {
3819             @Override
3820             protected void op() {
3821                 method.sar();
3822             }
3823         }.store();
3824     }
3825 
3826     private void loadASSIGN_SHL(final BinaryNode binaryNode) {
3827         new BinarySelfAssignment(binaryNode) {
3828             @Override
3829             protected void op() {
3830                 method.shl();
3831             }
3832         }.store();
3833     }
3834 
3835     private void loadASSIGN_SHR(final BinaryNode binaryNode) {
3836         new BinarySelfAssignment(binaryNode) {
3837             @Override
3838             protected void op() {
3839                 doSHR();
3840             }
3841 
3842         }.store();
3843     }
3844 
3845     private void doSHR() {
3846         // TODO: make SHR optimistic
3847         method.shr();
3848         toUint();
3849     }
3850 
3851     private void toUint() {
3852         JSType.TO_UINT32_I.invoke(method);
3853     }
3854 
3855     private void loadASSIGN_SUB(final BinaryNode binaryNode) {
3856         new BinaryOptimisticSelfAssignment(binaryNode) {
3857             @Override
3858             protected void op(final OptimisticOperation oo) {
3859                 method.sub(oo.getProgramPoint());
3860             }
3861         }.store();
3862     }
3863 
3864     /**
3865      * Helper class for binary arithmetic ops
3866      */
3867     private abstract class BinaryArith {
3868         protected abstract void op(int programPoint);
3869 
3870         protected void evaluate(final BinaryNode node, final TypeBounds resultBounds) {
3871             final TypeBounds numericBounds = resultBounds.booleanToInt().objectToNumber();
3872             new OptimisticOperation(node, numericBounds) {
3873                 @Override
3874                 void loadStack() {
3875                     final TypeBounds operandBounds;
3876                     boolean forceConversionSeparation = false;
3877                     if(numericBounds.narrowest == Type.NUMBER) {
3878                         // Result should be double always. Propagate it into the operands so we don't have lots of I2D
3879                         // and L2D after operand evaluation.
3880                         assert numericBounds.widest == Type.NUMBER;
3881                         operandBounds = numericBounds;
3882                     } else {
3883                         final boolean isOptimistic = isValid(getProgramPoint());
3884                         if(isOptimistic || node.isTokenType(TokenType.DIV) || node.isTokenType(TokenType.MOD)) {
3885                             operandBounds = new TypeBounds(node.getType(), Type.NUMBER);
3886                         } else {
3887                             // Non-optimistic, non-FP subtraction or multiplication. Allow them to overflow.
3888                             operandBounds = new TypeBounds(Type.narrowest(node.getWidestOperandType(),
3889                                     numericBounds.widest), Type.NUMBER);
3890                             forceConversionSeparation = node.getWidestOperationType().narrowerThan(numericBounds.widest);
3891                         }
3892                     }
3893                     loadBinaryOperands(node.lhs(), node.rhs(), operandBounds, false, forceConversionSeparation);
3894                 }
3895 
3896                 @Override
3897                 void consumeStack() {
3898                     op(getProgramPoint());
3899                 }
3900             }.emit();
3901         }
3902     }
3903 
3904     private void loadBIT_AND(final BinaryNode binaryNode) {
3905         loadBinaryOperands(binaryNode);
3906         method.and();
3907     }
3908 
3909     private void loadBIT_OR(final BinaryNode binaryNode) {
3910         // Optimize x|0 to (int)x
3911         if (isRhsZero(binaryNode)) {
3912             loadExpressionAsType(binaryNode.lhs(), Type.INT);
3913         } else {
3914             loadBinaryOperands(binaryNode);
3915             method.or();
3916         }
3917     }
3918 
3919     private static boolean isRhsZero(final BinaryNode binaryNode) {
3920         final Expression rhs = binaryNode.rhs();
3921         return rhs instanceof LiteralNode && INT_ZERO.equals(((LiteralNode<?>)rhs).getValue());
3922     }
3923 
3924     private void loadBIT_XOR(final BinaryNode binaryNode) {
3925         loadBinaryOperands(binaryNode);
3926         method.xor();
3927     }
3928 
3929     private void loadCOMMARIGHT(final BinaryNode binaryNode, final TypeBounds resultBounds) {
3930         loadAndDiscard(binaryNode.lhs());
3931         loadExpression(binaryNode.rhs(), resultBounds);
3932     }
3933 
3934     private void loadCOMMALEFT(final BinaryNode binaryNode, final TypeBounds resultBounds) {
3935         loadExpression(binaryNode.lhs(), resultBounds);
3936         loadAndDiscard(binaryNode.rhs());
3937     }
3938 
3939     private void loadDIV(final BinaryNode binaryNode, final TypeBounds resultBounds) {
3940         new BinaryArith() {
3941             @Override
3942             protected void op(final int programPoint) {
3943                 method.div(programPoint);
3944             }
3945         }.evaluate(binaryNode, resultBounds);
3946     }
3947 
3948     private void loadCmp(final BinaryNode binaryNode, final Condition cond) {
3949         assert comparisonOperandsArePrimitive(binaryNode) : binaryNode;
3950         loadBinaryOperands(binaryNode);
3951 
3952         final Label trueLabel  = new Label("trueLabel");
3953         final Label afterLabel = new Label("skip");
3954 
3955         method.conditionalJump(cond, trueLabel);
3956 
3957         method.load(Boolean.FALSE);
3958         method._goto(afterLabel);
3959         method.label(trueLabel);
3960         method.load(Boolean.TRUE);
3961         method.label(afterLabel);
3962     }
3963 
3964     private static boolean comparisonOperandsArePrimitive(final BinaryNode binaryNode) {
3965         final Type widest = Type.widest(binaryNode.lhs().getType(), binaryNode.rhs().getType());
3966         return widest.isNumeric() || widest.isBoolean();
3967     }
3968 
3969     private void loadMOD(final BinaryNode binaryNode, final TypeBounds resultBounds) {
3970         new BinaryArith() {
3971             @Override
3972             protected void op(final int programPoint) {
3973                 method.rem(programPoint);
3974             }
3975         }.evaluate(binaryNode, resultBounds);
3976     }
3977 
3978     private void loadMUL(final BinaryNode binaryNode, final TypeBounds resultBounds) {
3979         new BinaryArith() {
3980             @Override
3981             protected void op(final int programPoint) {
3982                 method.mul(programPoint);
3983             }
3984         }.evaluate(binaryNode, resultBounds);
3985     }
3986 
3987     private void loadSAR(final BinaryNode binaryNode) {
3988         loadBinaryOperands(binaryNode);
3989         method.sar();
3990     }
3991 
3992     private void loadSHL(final BinaryNode binaryNode) {
3993         loadBinaryOperands(binaryNode);
3994         method.shl();
3995     }
3996 
3997     private void loadSHR(final BinaryNode binaryNode) {
3998         // Optimize x >>> 0 to (uint)x
3999         if (isRhsZero(binaryNode)) {
4000             loadExpressionAsType(binaryNode.lhs(), Type.INT);
4001             toUint();
4002         } else {
4003             loadBinaryOperands(binaryNode);
4004             doSHR();
4005         }
4006     }
4007 
4008     private void loadSUB(final BinaryNode binaryNode, final TypeBounds resultBounds) {
4009         new BinaryArith() {
4010             @Override
4011             protected void op(final int programPoint) {
4012                 method.sub(programPoint);
4013             }
4014         }.evaluate(binaryNode, resultBounds);
4015     }
4016 
4017     @Override
4018     public boolean enterLabelNode(final LabelNode labelNode) {
4019         labeledBlockBreakLiveLocals.push(lc.getUsedSlotCount());
4020         return true;
4021     }
4022 
4023     @Override
4024     protected boolean enterDefault(final Node node) {
4025         throw new AssertionError("Code generator entered node of type " + node.getClass().getName());
4026     }
4027 
4028     private void loadTernaryNode(final TernaryNode ternaryNode, final TypeBounds resultBounds) {
4029         final Expression test = ternaryNode.getTest();
4030         final JoinPredecessorExpression trueExpr  = ternaryNode.getTrueExpression();
4031         final JoinPredecessorExpression falseExpr = ternaryNode.getFalseExpression();
4032 
4033         final Label falseLabel = new Label("ternary_false");
4034         final Label exitLabel  = new Label("ternary_exit");
4035 
4036         final Type outNarrowest = Type.narrowest(resultBounds.widest, Type.generic(Type.widestReturnType(trueExpr.getType(), falseExpr.getType())));
4037         final TypeBounds outBounds = resultBounds.notNarrowerThan(outNarrowest);
4038 
4039         emitBranch(test, falseLabel, false);
4040 
4041         loadExpression(trueExpr.getExpression(), outBounds);
4042         assert Type.generic(method.peekType()) == outBounds.narrowest;
4043         method.beforeJoinPoint(trueExpr);
4044         method._goto(exitLabel);
4045         method.label(falseLabel);
4046         loadExpression(falseExpr.getExpression(), outBounds);
4047         assert Type.generic(method.peekType()) == outBounds.narrowest;
4048         method.beforeJoinPoint(falseExpr);
4049         method.label(exitLabel);
4050     }
4051 
4052     /**
4053      * Generate all shared scope calls generated during codegen.
4054      */
4055     void generateScopeCalls() {
4056         for (final SharedScopeCall scopeAccess : lc.getScopeCalls()) {
4057             scopeAccess.generateScopeCall();
4058         }
4059     }
4060 
4061     /**
4062      * Debug code used to print symbols
4063      *
4064      * @param block the block we are in
4065      * @param function the function we are in
4066      * @param ident identifier for block or function where applicable
4067      */
4068     private void printSymbols(final Block block, final FunctionNode function, final String ident) {
4069         if (compiler.getScriptEnvironment()._print_symbols || function.getFlag(FunctionNode.IS_PRINT_SYMBOLS)) {
4070             final PrintWriter out = compiler.getScriptEnvironment().getErr();
4071             out.println("[BLOCK in '" + ident + "']");
4072             if (!block.printSymbols(out)) {
4073                 out.println("<no symbols>");
4074             }
4075             out.println();
4076         }
4077     }
4078 
4079 
4080     /**
4081      * The difference between a store and a self modifying store is that
4082      * the latter may load part of the target on the stack, e.g. the base
4083      * of an AccessNode or the base and index of an IndexNode. These are used
4084      * both as target and as an extra source. Previously it was problematic
4085      * for self modifying stores if the target/lhs didn't belong to one
4086      * of three trivial categories: IdentNode, AcessNodes, IndexNodes. In that
4087      * case it was evaluated and tagged as "resolved", which meant at the second
4088      * time the lhs of this store was read (e.g. in a = a (second) + b for a += b,
4089      * it would be evaluated to a nop in the scope and cause stack underflow
4090      *
4091      * see NASHORN-703
4092      *
4093      * @param <T>
4094      */
4095     private abstract class SelfModifyingStore<T extends Expression> extends Store<T> {
4096         protected SelfModifyingStore(final T assignNode, final Expression target) {
4097             super(assignNode, target);
4098         }
4099 
4100         @Override
4101         protected boolean isSelfModifying() {
4102             return true;
4103         }
4104     }
4105 
4106     /**
4107      * Helper class to generate stores
4108      */
4109     private abstract class Store<T extends Expression> {
4110 
4111         /** An assignment node, e.g. x += y */
4112         protected final T assignNode;
4113 
4114         /** The target node to store to, e.g. x */
4115         private final Expression target;
4116 
4117         /** How deep on the stack do the arguments go if this generates an indy call */
4118         private int depth;
4119 
4120         /** If we have too many arguments, we need temporary storage, this is stored in 'quick' */
4121         private IdentNode quick;
4122 
4123         /**
4124          * Constructor
4125          *
4126          * @param assignNode the node representing the whole assignment
4127          * @param target     the target node of the assignment (destination)
4128          */
4129         protected Store(final T assignNode, final Expression target) {
4130             this.assignNode = assignNode;
4131             this.target = target;
4132         }
4133 
4134         /**
4135          * Constructor
4136          *
4137          * @param assignNode the node representing the whole assignment
4138          */
4139         protected Store(final T assignNode) {
4140             this(assignNode, assignNode);
4141         }
4142 
4143         /**
4144          * Is this a self modifying store operation, e.g. *= or ++
4145          * @return true if self modifying store
4146          */
4147         protected boolean isSelfModifying() {
4148             return false;
4149         }
4150 
4151         private void prologue() {
4152             /**
4153              * This loads the parts of the target, e.g base and index. they are kept
4154              * on the stack throughout the store and used at the end to execute it
4155              */
4156 
4157             target.accept(new NodeVisitor<LexicalContext>(new LexicalContext()) {
4158                 @Override
4159                 public boolean enterIdentNode(final IdentNode node) {
4160                     if (node.getSymbol().isScope()) {
4161                         method.loadCompilerConstant(SCOPE);
4162                         depth += Type.SCOPE.getSlots();
4163                         assert depth == 1;
4164                     }
4165                     return false;
4166                 }
4167 
4168                 private void enterBaseNode() {
4169                     assert target instanceof BaseNode : "error - base node " + target + " must be instanceof BaseNode";
4170                     final BaseNode   baseNode = (BaseNode)target;
4171                     final Expression base     = baseNode.getBase();
4172 
4173                     loadExpressionAsObject(base);
4174                     depth += Type.OBJECT.getSlots();
4175                     assert depth == 1;
4176 
4177                     if (isSelfModifying()) {
4178                         method.dup();
4179                     }
4180                 }
4181 
4182                 @Override
4183                 public boolean enterAccessNode(final AccessNode node) {
4184                     enterBaseNode();
4185                     return false;
4186                 }
4187 
4188                 @Override
4189                 public boolean enterIndexNode(final IndexNode node) {
4190                     enterBaseNode();
4191 
4192                     final Expression index = node.getIndex();
4193                     if (!index.getType().isNumeric()) {
4194                         // could be boolean here as well
4195                         loadExpressionAsObject(index);
4196                     } else {
4197                         loadExpressionUnbounded(index);
4198                     }
4199                     depth += index.getType().getSlots();
4200 
4201                     if (isSelfModifying()) {
4202                         //convert "base base index" to "base index base index"
4203                         method.dup(1);
4204                     }
4205 
4206                     return false;
4207                 }
4208 
4209             });
4210         }
4211 
4212         /**
4213          * Generates an extra local variable, always using the same slot, one that is available after the end of the
4214          * frame.
4215          *
4216          * @param type the type of the variable
4217          *
4218          * @return the quick variable
4219          */
4220         private IdentNode quickLocalVariable(final Type type) {
4221             final String name = lc.getCurrentFunction().uniqueName(QUICK_PREFIX.symbolName());
4222             final Symbol symbol = new Symbol(name, IS_INTERNAL | HAS_SLOT);
4223             symbol.setHasSlotFor(type);
4224             symbol.setFirstSlot(lc.quickSlot(type));
4225 
4226             final IdentNode quickIdent = IdentNode.createInternalIdentifier(symbol).setType(type);
4227 
4228             return quickIdent;
4229         }
4230 
4231         // store the result that "lives on" after the op, e.g. "i" in i++ postfix.
4232         protected void storeNonDiscard() {
4233             if (lc.getCurrentDiscard() == assignNode) {
4234                 assert assignNode.isAssignment();
4235                 lc.popDiscard();
4236                 return;
4237             }
4238 
4239             if (method.dup(depth) == null) {
4240                 method.dup();
4241                 final Type quickType = method.peekType();
4242                 this.quick = quickLocalVariable(quickType);
4243                 final Symbol quickSymbol = quick.getSymbol();
4244                 method.storeTemp(quickType, quickSymbol.getFirstSlot());
4245             }
4246         }
4247 
4248         private void epilogue() {
4249             /**
4250              * Take the original target args from the stack and use them
4251              * together with the value to be stored to emit the store code
4252              *
4253              * The case that targetSymbol is in scope (!hasSlot) and we actually
4254              * need to do a conversion on non-equivalent types exists, but is
4255              * very rare. See for example test/script/basic/access-specializer.js
4256              */
4257             target.accept(new NodeVisitor<LexicalContext>(new LexicalContext()) {
4258                 @Override
4259                 protected boolean enterDefault(final Node node) {
4260                     throw new AssertionError("Unexpected node " + node + " in store epilogue");
4261                 }
4262 
4263                 @Override
4264                 public boolean enterIdentNode(final IdentNode node) {
4265                     final Symbol symbol = node.getSymbol();
4266                     assert symbol != null;
4267                     if (symbol.isScope()) {
4268                         final int flags = CALLSITE_SCOPE | getCallSiteFlags();
4269                         if (isFastScope(symbol)) {
4270                             storeFastScopeVar(symbol, flags);
4271                         } else {
4272                             method.dynamicSet(node.getName(), flags, false);
4273                         }
4274                     } else {
4275                         final Type storeType = assignNode.getType();
4276                         if (symbol.hasSlotFor(storeType)) {
4277                             // Only emit a convert for a store known to be live; converts for dead stores can
4278                             // give us an unnecessary ClassCastException.
4279                             method.convert(storeType);
4280                         }
4281                         storeIdentWithCatchConversion(node, storeType);
4282                     }
4283                     return false;
4284 
4285                 }
4286 
4287                 @Override
4288                 public boolean enterAccessNode(final AccessNode node) {
4289                     method.dynamicSet(node.getProperty(), getCallSiteFlags(), node.isIndex());
4290                     return false;
4291                 }
4292 
4293                 @Override
4294                 public boolean enterIndexNode(final IndexNode node) {
4295                     method.dynamicSetIndex(getCallSiteFlags());
4296                     return false;
4297                 }
4298             });
4299 
4300 
4301             // whatever is on the stack now is the final answer
4302         }
4303 
4304         protected abstract void evaluate();
4305 
4306         void store() {
4307             if (target instanceof IdentNode) {
4308                 checkTemporalDeadZone((IdentNode)target);
4309             }
4310             prologue();
4311             evaluate(); // leaves an operation of whatever the operationType was on the stack
4312             storeNonDiscard();
4313             epilogue();
4314             if (quick != null) {
4315                 method.load(quick);
4316             }
4317         }
4318     }
4319 
4320     private void newFunctionObject(final FunctionNode functionNode, final boolean addInitializer) {
4321         assert lc.peek() == functionNode;
4322 
4323         final RecompilableScriptFunctionData data = compiler.getScriptFunctionData(functionNode.getId());
4324 
4325         if (functionNode.isProgram() && !compiler.isOnDemandCompilation()) {
4326             final CompileUnit fnUnit = functionNode.getCompileUnit();
4327             final MethodEmitter createFunction = fnUnit.getClassEmitter().method(
4328                     EnumSet.of(Flag.PUBLIC, Flag.STATIC), CREATE_PROGRAM_FUNCTION.symbolName(),
4329                     ScriptFunction.class, ScriptObject.class);
4330             createFunction.begin();
4331             createFunction._new(SCRIPTFUNCTION_IMPL_NAME, SCRIPTFUNCTION_IMPL_TYPE).dup();
4332             loadConstant(data, fnUnit, createFunction);
4333             createFunction.load(SCOPE_TYPE, 0);
4334             createFunction.invoke(constructorNoLookup(SCRIPTFUNCTION_IMPL_NAME, RecompilableScriptFunctionData.class, ScriptObject.class));
4335             createFunction._return();
4336             createFunction.end();
4337         }
4338 
4339         if (addInitializer && !compiler.isOnDemandCompilation()) {
4340             compiler.addFunctionInitializer(data, functionNode);
4341         }
4342 
4343         // We don't emit a ScriptFunction on stack for the outermost compiled function (as there's no code being
4344         // generated in its outer context that'd need it as a callee).
4345         if (lc.getOutermostFunction() == functionNode) {
4346             return;
4347         }
4348 
4349         method._new(SCRIPTFUNCTION_IMPL_NAME, SCRIPTFUNCTION_IMPL_TYPE).dup();
4350         loadConstant(data);
4351 
4352         if (functionNode.needsParentScope()) {
4353             method.loadCompilerConstant(SCOPE);
4354         } else {
4355             method.loadNull();
4356         }
4357         method.invoke(constructorNoLookup(SCRIPTFUNCTION_IMPL_NAME, RecompilableScriptFunctionData.class, ScriptObject.class));
4358     }
4359 
4360     // calls on Global class.
4361     private MethodEmitter globalInstance() {
4362         return method.invokestatic(GLOBAL_OBJECT, "instance", "()L" + GLOBAL_OBJECT + ';');
4363     }
4364 
4365     private MethodEmitter globalAllocateArguments() {
4366         return method.invokestatic(GLOBAL_OBJECT, "allocateArguments", methodDescriptor(ScriptObject.class, Object[].class, Object.class, int.class));
4367     }
4368 
4369     private MethodEmitter globalNewRegExp() {
4370         return method.invokestatic(GLOBAL_OBJECT, "newRegExp", methodDescriptor(Object.class, String.class, String.class));
4371     }
4372 
4373     private MethodEmitter globalRegExpCopy() {
4374         return method.invokestatic(GLOBAL_OBJECT, "regExpCopy", methodDescriptor(Object.class, Object.class));
4375     }
4376 
4377     private MethodEmitter globalAllocateArray(final ArrayType type) {
4378         //make sure the native array is treated as an array type
4379         return method.invokestatic(GLOBAL_OBJECT, "allocate", "(" + type.getDescriptor() + ")Ljdk/nashorn/internal/objects/NativeArray;");
4380     }
4381 
4382     private MethodEmitter globalIsEval() {
4383         return method.invokestatic(GLOBAL_OBJECT, "isEval", methodDescriptor(boolean.class, Object.class));
4384     }
4385 
4386     private MethodEmitter globalReplaceLocationPropertyPlaceholder() {
4387         return method.invokestatic(GLOBAL_OBJECT, "replaceLocationPropertyPlaceholder", methodDescriptor(Object.class, Object.class, Object.class));
4388     }
4389 
4390     private MethodEmitter globalCheckObjectCoercible() {
4391         return method.invokestatic(GLOBAL_OBJECT, "checkObjectCoercible", methodDescriptor(void.class, Object.class));
4392     }
4393 
4394     private MethodEmitter globalDirectEval() {
4395         return method.invokestatic(GLOBAL_OBJECT, "directEval",
4396                 methodDescriptor(Object.class, Object.class, Object.class, Object.class, Object.class, boolean.class));
4397     }
4398 
4399     private abstract class OptimisticOperation {
4400         private final boolean isOptimistic;
4401         // expression and optimistic are the same reference
4402         private final Expression expression;
4403         private final Optimistic optimistic;
4404         private final TypeBounds resultBounds;
4405 
4406         OptimisticOperation(final Optimistic optimistic, final TypeBounds resultBounds) {
4407             this.optimistic = optimistic;
4408             this.expression = (Expression)optimistic;
4409             this.resultBounds = resultBounds;
4410             this.isOptimistic = isOptimistic(optimistic) && useOptimisticTypes() &&
4411                     // Operation is only effectively optimistic if its type, after being coerced into the result bounds
4412                     // is narrower than the upper bound.
4413                     resultBounds.within(Type.generic(((Expression)optimistic).getType())).narrowerThan(resultBounds.widest);
4414         }
4415 
4416         MethodEmitter emit() {
4417             return emit(0);
4418         }
4419 
4420         MethodEmitter emit(final int ignoredArgCount) {
4421             final int     programPoint                  = optimistic.getProgramPoint();
4422             final boolean optimisticOrContinuation      = isOptimistic || isContinuationEntryPoint(programPoint);
4423             final boolean currentContinuationEntryPoint = isCurrentContinuationEntryPoint(programPoint);
4424             final int     stackSizeOnEntry              = method.getStackSize() - ignoredArgCount;
4425 
4426             // First store the values on the stack opportunistically into local variables. Doing it before loadStack()
4427             // allows us to not have to pop/load any arguments that are pushed onto it by loadStack() in the second
4428             // storeStack().
4429             storeStack(ignoredArgCount, optimisticOrContinuation);
4430 
4431             // Now, load the stack
4432             loadStack();
4433 
4434             // Now store the values on the stack ultimately into local variables. In vast majority of cases, this is
4435             // (aside from creating the local types map) a no-op, as the first opportunistic stack store will already
4436             // store all variables. However, there can be operations in the loadStack() that invalidate some of the
4437             // stack stores, e.g. in "x[i] = x[++i]", "++i" will invalidate the already stored value for "i". In such
4438             // unfortunate cases this second storeStack() will restore the invariant that everything on the stack is
4439             // stored into a local variable, although at the cost of doing a store/load on the loaded arguments as well.
4440             final int liveLocalsCount = storeStack(method.getStackSize() - stackSizeOnEntry, optimisticOrContinuation);
4441             assert optimisticOrContinuation == (liveLocalsCount != -1);
4442 
4443             final Label beginTry;
4444             final Label catchLabel;
4445             final Label afterConsumeStack = isOptimistic || currentContinuationEntryPoint ? new Label("after_consume_stack") : null;
4446             if(isOptimistic) {
4447                 beginTry = new Label("try_optimistic");
4448                 final String catchLabelName = (afterConsumeStack == null ? "" : afterConsumeStack.toString()) + "_handler";
4449                 catchLabel = new Label(catchLabelName);
4450                 method.label(beginTry);
4451             } else {
4452                 beginTry = catchLabel = null;
4453             }
4454 
4455             consumeStack();
4456 
4457             if(isOptimistic) {
4458                 method._try(beginTry, afterConsumeStack, catchLabel, UnwarrantedOptimismException.class);
4459             }
4460 
4461             if(isOptimistic || currentContinuationEntryPoint) {
4462                 method.label(afterConsumeStack);
4463 
4464                 final int[] localLoads = method.getLocalLoadsOnStack(0, stackSizeOnEntry);
4465                 assert everyStackValueIsLocalLoad(localLoads) : Arrays.toString(localLoads) + ", " + stackSizeOnEntry + ", " + ignoredArgCount;
4466                 final List<Type> localTypesList = method.getLocalVariableTypes();
4467                 final int usedLocals = method.getUsedSlotsWithLiveTemporaries();
4468                 final List<Type> localTypes = method.getWidestLiveLocals(localTypesList.subList(0, usedLocals));
4469                 assert everyLocalLoadIsValid(localLoads, usedLocals) : Arrays.toString(localLoads) + " ~ " + localTypes;
4470 
4471                 if(isOptimistic) {
4472                     addUnwarrantedOptimismHandlerLabel(localTypes, catchLabel);
4473                 }
4474                 if(currentContinuationEntryPoint) {
4475                     final ContinuationInfo ci = getContinuationInfo();
4476                     assert ci != null : "no continuation info found for " + lc.getCurrentFunction();
4477                     assert !ci.hasTargetLabel(); // No duplicate program points
4478                     ci.setTargetLabel(afterConsumeStack);
4479                     ci.getHandlerLabel().markAsOptimisticContinuationHandlerFor(afterConsumeStack);
4480                     // Can't rely on targetLabel.stack.localVariableTypes.length, as it can be higher due to effectively
4481                     // dead local variables.
4482                     ci.lvarCount = localTypes.size();
4483                     ci.setStackStoreSpec(localLoads);
4484                     ci.setStackTypes(Arrays.copyOf(method.getTypesFromStack(method.getStackSize()), stackSizeOnEntry));
4485                     assert ci.getStackStoreSpec().length == ci.getStackTypes().length;
4486                     ci.setReturnValueType(method.peekType());
4487                     ci.lineNumber = getLastLineNumber();
4488                     ci.catchLabel = catchLabels.peek();
4489                 }
4490             }
4491             return method;
4492         }
4493 
4494         /**
4495          * Stores the current contents of the stack into local variables so they are not lost before invoking something that
4496          * can result in an {@code UnwarantedOptimizationException}.
4497          * @param ignoreArgCount the number of topmost arguments on stack to ignore when deciding on the shape of the catch
4498          * block. Those are used in the situations when we could not place the call to {@code storeStack} early enough
4499          * (before emitting code for pushing the arguments that the optimistic call will pop). This is admittedly a
4500          * deficiency in the design of the code generator when it deals with self-assignments and we should probably look
4501          * into fixing it.
4502          * @return types of the significant local variables after the stack was stored (types for local variables used
4503          * for temporary storage of ignored arguments are not returned).
4504          * @param optimisticOrContinuation if false, this method should not execute
4505          * a label for a catch block for the {@code UnwarantedOptimizationException}, suitable for capturing the
4506          * currently live local variables, tailored to their types.
4507          */
4508         private int storeStack(final int ignoreArgCount, final boolean optimisticOrContinuation) {
4509             if(!optimisticOrContinuation) {
4510                 return -1; // NOTE: correct value to return is lc.getUsedSlotCount(), but it wouldn't be used anyway
4511             }
4512 
4513             final int stackSize = method.getStackSize();
4514             final Type[] stackTypes = method.getTypesFromStack(stackSize);
4515             final int[] localLoadsOnStack = method.getLocalLoadsOnStack(0, stackSize);
4516             final int usedSlots = method.getUsedSlotsWithLiveTemporaries();
4517 
4518             final int firstIgnored = stackSize - ignoreArgCount;
4519             // Find the first value on the stack (from the bottom) that is not a load from a local variable.
4520             int firstNonLoad = 0;
4521             while(firstNonLoad < firstIgnored && localLoadsOnStack[firstNonLoad] != Label.Stack.NON_LOAD) {
4522                 firstNonLoad++;
4523             }
4524 
4525             // Only do the store/load if first non-load is not an ignored argument. Otherwise, do nothing and return
4526             // the number of used slots as the number of live local variables.
4527             if(firstNonLoad >= firstIgnored) {
4528                 return usedSlots;
4529             }
4530 
4531             // Find the number of new temporary local variables that we need; it's the number of values on the stack that
4532             // are not direct loads of existing local variables.
4533             int tempSlotsNeeded = 0;
4534             for(int i = firstNonLoad; i < stackSize; ++i) {
4535                 if(localLoadsOnStack[i] == Label.Stack.NON_LOAD) {
4536                     tempSlotsNeeded += stackTypes[i].getSlots();
4537                 }
4538             }
4539 
4540             // Ensure all values on the stack that weren't directly loaded from a local variable are stored in a local
4541             // variable. We're starting from highest local variable index, so that in case ignoreArgCount > 0 the ignored
4542             // ones end up at the end of the local variable table.
4543             int lastTempSlot = usedSlots + tempSlotsNeeded;
4544             int ignoreSlotCount = 0;
4545             for(int i = stackSize; i -- > firstNonLoad;) {
4546                 final int loadSlot = localLoadsOnStack[i];
4547                 if(loadSlot == Label.Stack.NON_LOAD) {
4548                     final Type type = stackTypes[i];
4549                     final int slots = type.getSlots();
4550                     lastTempSlot -= slots;
4551                     if(i >= firstIgnored) {
4552                         ignoreSlotCount += slots;
4553                     }
4554                     method.storeTemp(type, lastTempSlot);
4555                 } else {
4556                     method.pop();
4557                 }
4558             }
4559             assert lastTempSlot == usedSlots; // used all temporary locals
4560 
4561             final List<Type> localTypesList = method.getLocalVariableTypes();
4562 
4563             // Load values back on stack.
4564             for(int i = firstNonLoad; i < stackSize; ++i) {
4565                 final int loadSlot = localLoadsOnStack[i];
4566                 final Type stackType = stackTypes[i];
4567                 final boolean isLoad = loadSlot != Label.Stack.NON_LOAD;
4568                 final int lvarSlot = isLoad ? loadSlot : lastTempSlot;
4569                 final Type lvarType = localTypesList.get(lvarSlot);
4570                 method.load(lvarType, lvarSlot);
4571                 if(isLoad) {
4572                     // Conversion operators (I2L etc.) preserve "load"-ness of the value despite the fact that, in the
4573                     // strict sense they are creating a derived value from the loaded value. This special behavior of
4574                     // on-stack conversion operators is necessary to accommodate for differences in local variable types
4575                     // after deoptimization; having a conversion operator throw away "load"-ness would create different
4576                     // local variable table shapes between optimism-failed code and its deoptimized rest-of method).
4577                     // After we load the value back, we need to redo the conversion to the stack type if stack type is
4578                     // different.
4579                     // NOTE: this would only strictly be necessary for widening conversions (I2L, L2D, I2D), and not for
4580                     // narrowing ones (L2I, D2L, D2I) as only widening conversions are the ones that can get eliminated
4581                     // in a deoptimized method, as their original input argument got widened. Maybe experiment with
4582                     // throwing away "load"-ness for narrowing conversions in MethodEmitter.convert()?
4583                     method.convert(stackType);
4584                 } else {
4585                     // temporary stores never needs a convert, as their type is always the same as the stack type.
4586                     assert lvarType == stackType;
4587                     lastTempSlot += lvarType.getSlots();
4588                 }
4589             }
4590             // used all temporaries
4591             assert lastTempSlot == usedSlots + tempSlotsNeeded;
4592 
4593             return lastTempSlot - ignoreSlotCount;
4594         }
4595 
4596         private void addUnwarrantedOptimismHandlerLabel(final List<Type> localTypes, final Label label) {
4597             final String lvarTypesDescriptor = getLvarTypesDescriptor(localTypes);
4598             final Map<String, Collection<Label>> unwarrantedOptimismHandlers = lc.getUnwarrantedOptimismHandlers();
4599             Collection<Label> labels = unwarrantedOptimismHandlers.get(lvarTypesDescriptor);
4600             if(labels == null) {
4601                 labels = new LinkedList<>();
4602                 unwarrantedOptimismHandlers.put(lvarTypesDescriptor, labels);
4603             }
4604             method.markLabelAsOptimisticCatchHandler(label, localTypes.size());
4605             labels.add(label);
4606         }
4607 
4608         abstract void loadStack();
4609 
4610         // Make sure that whatever indy call site you emit from this method uses {@code getCallSiteFlagsOptimistic(node)}
4611         // or otherwise ensure optimistic flag is correctly set in the call site, otherwise it doesn't make much sense
4612         // to use OptimisticExpression for emitting it.
4613         abstract void consumeStack();
4614 
4615         /**
4616          * Emits the correct dynamic getter code. Normally just delegates to method emitter, except when the target
4617          * expression is optimistic, and the desired type is narrower than the optimistic type. In that case, it'll emit a
4618          * dynamic getter with its original optimistic type, and explicitly insert a narrowing conversion. This way we can
4619          * preserve the optimism of the values even if they're subsequently immediately coerced into a narrower type. This
4620          * is beneficial because in this case we can still presume that since the original getter was optimistic, the
4621          * conversion has no side effects.
4622          * @param name the name of the property being get
4623          * @param flags call site flags
4624          * @param isMethod whether we're preferrably retrieving a function
4625          * @return the current method emitter
4626          */
4627         MethodEmitter dynamicGet(final String name, final int flags, final boolean isMethod, final boolean isIndex) {
4628             if(isOptimistic) {
4629                 return method.dynamicGet(getOptimisticCoercedType(), name, getOptimisticFlags(flags), isMethod, isIndex);
4630             }
4631             return method.dynamicGet(resultBounds.within(expression.getType()), name, nonOptimisticFlags(flags), isMethod, isIndex);
4632         }
4633 
4634         MethodEmitter dynamicGetIndex(final int flags, final boolean isMethod) {
4635             if(isOptimistic) {
4636                 return method.dynamicGetIndex(getOptimisticCoercedType(), getOptimisticFlags(flags), isMethod);
4637             }
4638             return method.dynamicGetIndex(resultBounds.within(expression.getType()), nonOptimisticFlags(flags), isMethod);
4639         }
4640 
4641         MethodEmitter dynamicCall(final int argCount, final int flags) {
4642             if (isOptimistic) {
4643                 return method.dynamicCall(getOptimisticCoercedType(), argCount, getOptimisticFlags(flags));
4644             }
4645             return method.dynamicCall(resultBounds.within(expression.getType()), argCount, nonOptimisticFlags(flags));
4646         }
4647 
4648         int getOptimisticFlags(final int flags) {
4649             return flags | CALLSITE_OPTIMISTIC | (optimistic.getProgramPoint() << CALLSITE_PROGRAM_POINT_SHIFT); //encode program point in high bits
4650         }
4651 
4652         int getProgramPoint() {
4653             return isOptimistic ? optimistic.getProgramPoint() : INVALID_PROGRAM_POINT;
4654         }
4655 
4656         void convertOptimisticReturnValue() {
4657             if (isOptimistic) {
4658                 final Type optimisticType = getOptimisticCoercedType();
4659                 if(!optimisticType.isObject()) {
4660                     method.load(optimistic.getProgramPoint());
4661                     if(optimisticType.isInteger()) {
4662                         method.invoke(ENSURE_INT);
4663                     } else if(optimisticType.isLong()) {
4664                         method.invoke(ENSURE_LONG);
4665                     } else if(optimisticType.isNumber()) {
4666                         method.invoke(ENSURE_NUMBER);
4667                     } else {
4668                         throw new AssertionError(optimisticType);
4669                     }
4670                 }
4671             }
4672         }
4673 
4674         void replaceCompileTimeProperty() {
4675             final IdentNode identNode = (IdentNode)expression;
4676             final String name = identNode.getSymbol().getName();
4677             if (CompilerConstants.__FILE__.name().equals(name)) {
4678                 replaceCompileTimeProperty(getCurrentSource().getName());
4679             } else if (CompilerConstants.__DIR__.name().equals(name)) {
4680                 replaceCompileTimeProperty(getCurrentSource().getBase());
4681             } else if (CompilerConstants.__LINE__.name().equals(name)) {
4682                 replaceCompileTimeProperty(getCurrentSource().getLine(identNode.position()));
4683             }
4684         }
4685 
4686         /**
4687          * When an ident with name __FILE__, __DIR__, or __LINE__ is loaded, we'll try to look it up as any other
4688          * identifier. However, if it gets all the way up to the Global object, it will send back a special value that
4689          * represents a placeholder for these compile-time location properties. This method will generate code that loads
4690          * the value of the compile-time location property and then invokes a method in Global that will replace the
4691          * placeholder with the value. Effectively, if the symbol for these properties is defined anywhere in the lexical
4692          * scope, they take precedence, but if they aren't, then they resolve to the compile-time location property.
4693          * @param propertyValue the actual value of the property
4694          */
4695         private void replaceCompileTimeProperty(final Object propertyValue) {
4696             assert method.peekType().isObject();
4697             if(propertyValue instanceof String || propertyValue == null) {
4698                 method.load((String)propertyValue);
4699             } else if(propertyValue instanceof Integer) {
4700                 method.load(((Integer)propertyValue).intValue());
4701                 method.convert(Type.OBJECT);
4702             } else {
4703                 throw new AssertionError();
4704             }
4705             globalReplaceLocationPropertyPlaceholder();
4706             convertOptimisticReturnValue();
4707         }
4708 
4709         /**
4710          * Returns the type that should be used as the return type of the dynamic invocation that is emitted as the code
4711          * for the current optimistic operation. If the type bounds is exact boolean or narrower than the expression's
4712          * optimistic type, then the optimistic type is returned, otherwise the coercing type. Effectively, this method
4713          * allows for moving the coercion into the optimistic type when it won't adversely affect the optimistic
4714          * evaluation semantics, and for preserving the optimistic type and doing a separate coercion when it would
4715          * affect it.
4716          * @return
4717          */
4718         private Type getOptimisticCoercedType() {
4719             final Type optimisticType = expression.getType();
4720             assert resultBounds.widest.widerThan(optimisticType);
4721             final Type narrowest = resultBounds.narrowest;
4722 
4723             if(narrowest.isBoolean() || narrowest.narrowerThan(optimisticType)) {
4724                 assert !optimisticType.isObject();
4725                 return optimisticType;
4726             }
4727             assert !narrowest.isObject();
4728             return narrowest;
4729         }
4730     }
4731 
4732     private static boolean isOptimistic(final Optimistic optimistic) {
4733         if(!optimistic.canBeOptimistic()) {
4734             return false;
4735         }
4736         final Expression expr = (Expression)optimistic;
4737         return expr.getType().narrowerThan(expr.getWidestOperationType());
4738     }
4739 
4740     private static boolean everyLocalLoadIsValid(final int[] loads, final int localCount) {
4741         for (final int load : loads) {
4742             if(load < 0 || load >= localCount) {
4743                 return false;
4744             }
4745         }
4746         return true;
4747     }
4748 
4749     private static boolean everyStackValueIsLocalLoad(final int[] loads) {
4750         for (final int load : loads) {
4751             if(load == Label.Stack.NON_LOAD) {
4752                 return false;
4753             }
4754         }
4755         return true;
4756     }
4757 
4758     private String getLvarTypesDescriptor(final List<Type> localVarTypes) {
4759         final int count = localVarTypes.size();
4760         final StringBuilder desc = new StringBuilder(count);
4761         for(int i = 0; i < count;) {
4762             i += appendType(desc, localVarTypes.get(i));
4763         }
4764         return method.markSymbolBoundariesInLvarTypesDescriptor(desc.toString());
4765     }
4766 
4767     private static int appendType(final StringBuilder b, final Type t) {
4768         b.append(t.getBytecodeStackType());
4769         return t.getSlots();
4770     }
4771 
4772     private static int countSymbolsInLvarTypeDescriptor(final String lvarTypeDescriptor) {
4773         int count = 0;
4774         for(int i = 0; i < lvarTypeDescriptor.length(); ++i) {
4775             if(Character.isUpperCase(lvarTypeDescriptor.charAt(i))) {
4776                 ++count;
4777             }
4778         }
4779         return count;
4780 
4781     }
4782     /**
4783      * Generates all the required {@code UnwarrantedOptimismException} handlers for the current function. The employed
4784      * strategy strives to maximize code reuse. Every handler constructs an array to hold the local variables, then
4785      * fills in some trailing part of the local variables (those for which it has a unique suffix in the descriptor),
4786      * then jumps to a handler for a prefix that's shared with other handlers. A handler that fills up locals up to
4787      * position 0 will not jump to a prefix handler (as it has no prefix), but instead end with constructing and
4788      * throwing a {@code RewriteException}. Since we lexicographically sort the entries, we only need to check every
4789      * entry to its immediately preceding one for longest matching prefix.
4790      * @return true if there is at least one exception handler
4791      */
4792     private boolean generateUnwarrantedOptimismExceptionHandlers(final FunctionNode fn) {
4793         if(!useOptimisticTypes()) {
4794             return false;
4795         }
4796 
4797         // Take the mapping of lvarSpecs -> labels, and turn them into a descending lexicographically sorted list of
4798         // handler specifications.
4799         final Map<String, Collection<Label>> unwarrantedOptimismHandlers = lc.popUnwarrantedOptimismHandlers();
4800         if(unwarrantedOptimismHandlers.isEmpty()) {
4801             return false;
4802         }
4803 
4804         method.lineNumber(0);
4805 
4806         final List<OptimismExceptionHandlerSpec> handlerSpecs = new ArrayList<>(unwarrantedOptimismHandlers.size() * 4/3);
4807         for(final String spec: unwarrantedOptimismHandlers.keySet()) {
4808             handlerSpecs.add(new OptimismExceptionHandlerSpec(spec, true));
4809         }
4810         Collections.sort(handlerSpecs, Collections.reverseOrder());
4811 
4812         // Map of local variable specifications to labels for populating the array for that local variable spec.
4813         final Map<String, Label> delegationLabels = new HashMap<>();
4814 
4815         // Do everything in a single pass over the handlerSpecs list. Note that the list can actually grow as we're
4816         // passing through it as we might add new prefix handlers into it, so can't hoist size() outside of the loop.
4817         for(int handlerIndex = 0; handlerIndex < handlerSpecs.size(); ++handlerIndex) {
4818             final OptimismExceptionHandlerSpec spec = handlerSpecs.get(handlerIndex);
4819             final String lvarSpec = spec.lvarSpec;
4820             if(spec.catchTarget) {
4821                 assert !method.isReachable();
4822                 // Start a catch block and assign the labels for this lvarSpec with it.
4823                 method._catch(unwarrantedOptimismHandlers.get(lvarSpec));
4824                 // This spec is a catch target, so emit array creation code. The length of the array is the number of
4825                 // symbols - the number of uppercase characters.
4826                 method.load(countSymbolsInLvarTypeDescriptor(lvarSpec));
4827                 method.newarray(Type.OBJECT_ARRAY);
4828             }
4829             if(spec.delegationTarget) {
4830                 // If another handler can delegate to this handler as its prefix, then put a jump target here for the
4831                 // shared code (after the array creation code, which is never shared).
4832                 method.label(delegationLabels.get(lvarSpec)); // label must exist
4833             }
4834 
4835             final boolean lastHandler = handlerIndex == handlerSpecs.size() - 1;
4836 
4837             int lvarIndex;
4838             final int firstArrayIndex;
4839             final int firstLvarIndex;
4840             Label delegationLabel;
4841             final String commonLvarSpec;
4842             if(lastHandler) {
4843                 // Last handler block, doesn't delegate to anything.
4844                 lvarIndex = 0;
4845                 firstLvarIndex = 0;
4846                 firstArrayIndex = 0;
4847                 delegationLabel = null;
4848                 commonLvarSpec = null;
4849             } else {
4850                 // Not yet the last handler block, will definitely delegate to another handler; let's figure out which
4851                 // one. It can be an already declared handler further down the list, or it might need to declare a new
4852                 // prefix handler.
4853 
4854                 // Since we're lexicographically ordered, the common prefix handler is defined by the common prefix of
4855                 // this handler and the next handler on the list.
4856                 final int nextHandlerIndex = handlerIndex + 1;
4857                 final String nextLvarSpec = handlerSpecs.get(nextHandlerIndex).lvarSpec;
4858                 commonLvarSpec = commonPrefix(lvarSpec, nextLvarSpec);
4859                 // We don't chop symbols in half
4860                 assert Character.isUpperCase(commonLvarSpec.charAt(commonLvarSpec.length() - 1));
4861 
4862                 // Let's find if we already have a declaration for such handler, or we need to insert it.
4863                 {
4864                     boolean addNewHandler = true;
4865                     int commonHandlerIndex = nextHandlerIndex;
4866                     for(; commonHandlerIndex < handlerSpecs.size(); ++commonHandlerIndex) {
4867                         final OptimismExceptionHandlerSpec forwardHandlerSpec = handlerSpecs.get(commonHandlerIndex);
4868                         final String forwardLvarSpec = forwardHandlerSpec.lvarSpec;
4869                         if(forwardLvarSpec.equals(commonLvarSpec)) {
4870                             // We already have a handler for the common prefix.
4871                             addNewHandler = false;
4872                             // Make sure we mark it as a delegation target.
4873                             forwardHandlerSpec.delegationTarget = true;
4874                             break;
4875                         } else if(!forwardLvarSpec.startsWith(commonLvarSpec)) {
4876                             break;
4877                         }
4878                     }
4879                     if(addNewHandler) {
4880                         // We need to insert a common prefix handler. Note handlers created with catchTarget == false
4881                         // will automatically have delegationTarget == true (because that's the only reason for their
4882                         // existence).
4883                         handlerSpecs.add(commonHandlerIndex, new OptimismExceptionHandlerSpec(commonLvarSpec, false));
4884                     }
4885                 }
4886 
4887                 firstArrayIndex = countSymbolsInLvarTypeDescriptor(commonLvarSpec);
4888                 lvarIndex = 0;
4889                 for(int j = 0; j < commonLvarSpec.length(); ++j) {
4890                     lvarIndex += CodeGeneratorLexicalContext.getTypeForSlotDescriptor(commonLvarSpec.charAt(j)).getSlots();
4891                 }
4892                 firstLvarIndex = lvarIndex;
4893 
4894                 // Create a delegation label if not already present
4895                 delegationLabel = delegationLabels.get(commonLvarSpec);
4896                 if(delegationLabel == null) {
4897                     // uo_pa == "unwarranted optimism, populate array"
4898                     delegationLabel = new Label("uo_pa_" + commonLvarSpec);
4899                     delegationLabels.put(commonLvarSpec, delegationLabel);
4900                 }
4901             }
4902 
4903             // Load local variables handled by this handler on stack
4904             int args = 0;
4905             boolean symbolHadValue = false;
4906             for(int typeIndex = commonLvarSpec == null ? 0 : commonLvarSpec.length(); typeIndex < lvarSpec.length(); ++typeIndex) {
4907                 final char typeDesc = lvarSpec.charAt(typeIndex);
4908                 final Type lvarType = CodeGeneratorLexicalContext.getTypeForSlotDescriptor(typeDesc);
4909                 if (!lvarType.isUnknown()) {
4910                     method.load(lvarType, lvarIndex);
4911                     symbolHadValue = true;
4912                     args++;
4913                 } else if(typeDesc == 'U' && !symbolHadValue) {
4914                     // Symbol boundary with undefined last value. Check if all previous values for this symbol were also
4915                     // undefined; if so, emit one explicit Undefined. This serves to ensure that we're emiting exactly
4916                     // one value for every symbol that uses local slots. While we could in theory ignore symbols that
4917                     // are undefined (in other words, dead) at the point where this exception was thrown, unfortunately
4918                     // we can't do it in practice. The reason for this is that currently our liveness analysis is
4919                     // coarse (it can determine whether a symbol has not been read with a particular type anywhere in
4920                     // the function being compiled, but that's it), and a symbol being promoted to Object due to a
4921                     // deoptimization will suddenly show up as "live for Object type", and previously dead U->O
4922                     // conversions on loop entries will suddenly become alive in the deoptimized method which will then
4923                     // expect a value for that slot in its continuation handler. If we had precise liveness analysis, we
4924                     // could go back to excluding known dead symbols from the payload of the RewriteException.
4925                     if(method.peekType() == Type.UNDEFINED) {
4926                         method.dup();
4927                     } else {
4928                         method.loadUndefined(Type.OBJECT);
4929                     }
4930                     args++;
4931                 }
4932                 if(Character.isUpperCase(typeDesc)) {
4933                     // Reached symbol boundary; reset flag for the next symbol.
4934                     symbolHadValue = false;
4935                 }
4936                 lvarIndex += lvarType.getSlots();
4937             }
4938             assert args > 0;
4939             // Delegate actual storing into array to an array populator utility method.
4940             //on the stack:
4941             // object array to be populated
4942             // start index
4943             // a lot of types
4944             method.dynamicArrayPopulatorCall(args + 1, firstArrayIndex);
4945             if(delegationLabel != null) {
4946                 // We cascade to a prefix handler to fill out the rest of the local variables and throw the
4947                 // RewriteException.
4948                 assert !lastHandler;
4949                 assert commonLvarSpec != null;
4950                 // Must undefine the local variables that we have already processed for the sake of correct join on the
4951                 // delegate label
4952                 method.undefineLocalVariables(firstLvarIndex, true);
4953                 final OptimismExceptionHandlerSpec nextSpec = handlerSpecs.get(handlerIndex + 1);
4954                 // If the delegate immediately follows, and it's not a catch target (so it doesn't have array setup
4955                 // code) don't bother emitting a jump, as we'd just jump to the next instruction.
4956                 if(!nextSpec.lvarSpec.equals(commonLvarSpec) || nextSpec.catchTarget) {
4957                     method._goto(delegationLabel);
4958                 }
4959             } else {
4960                 assert lastHandler;
4961                 // Nothing to delegate to, so this handler must create and throw the RewriteException.
4962                 // At this point we have the UnwarrantedOptimismException and the Object[] with local variables on
4963                 // stack. We need to create a RewriteException, push two references to it below the constructor
4964                 // arguments, invoke the constructor, and throw the exception.
4965                 loadConstant(getByteCodeSymbolNames(fn));
4966                 if (isRestOf()) {
4967                     loadConstant(getContinuationEntryPoints());
4968                     method.invoke(CREATE_REWRITE_EXCEPTION_REST_OF);
4969                 } else {
4970                     method.invoke(CREATE_REWRITE_EXCEPTION);
4971                 }
4972                 method.athrow();
4973             }
4974         }
4975         return true;
4976     }
4977 
4978     private static String[] getByteCodeSymbolNames(final FunctionNode fn) {
4979         // Only names of local variables on the function level are captured. This information is used to reduce
4980         // deoptimizations, so as much as we can capture will help. We rely on the fact that function wide variables are
4981         // all live all the time, so the array passed to rewrite exception contains one element for every slotted symbol
4982         // here.
4983         final List<String> names = new ArrayList<>();
4984         for (final Symbol symbol: fn.getBody().getSymbols()) {
4985             if (symbol.hasSlot()) {
4986                 if (symbol.isScope()) {
4987                     // slot + scope can only be true for parameters
4988                     assert symbol.isParam();
4989                     names.add(null);
4990                 } else {
4991                     names.add(symbol.getName());
4992                 }
4993             }
4994         }
4995         return names.toArray(new String[names.size()]);
4996     }
4997 
4998     private static String commonPrefix(final String s1, final String s2) {
4999         final int l1 = s1.length();
5000         final int l = Math.min(l1, s2.length());
5001         int lms = -1; // last matching symbol
5002         for(int i = 0; i < l; ++i) {
5003             final char c1 = s1.charAt(i);
5004             if(c1 != s2.charAt(i)) {
5005                 return s1.substring(0, lms + 1);
5006             } else if(Character.isUpperCase(c1)) {
5007                 lms = i;
5008             }
5009         }
5010         return l == l1 ? s1 : s2;
5011     }
5012 
5013     private static class OptimismExceptionHandlerSpec implements Comparable<OptimismExceptionHandlerSpec> {
5014         private final String lvarSpec;
5015         private final boolean catchTarget;
5016         private boolean delegationTarget;
5017 
5018         OptimismExceptionHandlerSpec(final String lvarSpec, final boolean catchTarget) {
5019             this.lvarSpec = lvarSpec;
5020             this.catchTarget = catchTarget;
5021             if(!catchTarget) {
5022                 delegationTarget = true;
5023             }
5024         }
5025 
5026         @Override
5027         public int compareTo(final OptimismExceptionHandlerSpec o) {
5028             return lvarSpec.compareTo(o.lvarSpec);
5029         }
5030 
5031         @Override
5032         public String toString() {
5033             final StringBuilder b = new StringBuilder(64).append("[HandlerSpec ").append(lvarSpec);
5034             if(catchTarget) {
5035                 b.append(", catchTarget");
5036             }
5037             if(delegationTarget) {
5038                 b.append(", delegationTarget");
5039             }
5040             return b.append("]").toString();
5041         }
5042     }
5043 
5044     private static class ContinuationInfo {
5045         private final Label handlerLabel;
5046         private Label targetLabel; // Label for the target instruction.
5047         int lvarCount;
5048         // Indices of local variables that need to be loaded on the stack when this node completes
5049         private int[] stackStoreSpec;
5050         // Types of values loaded on the stack
5051         private Type[] stackTypes;
5052         // If non-null, this node should perform the requisite type conversion
5053         private Type returnValueType;
5054         // If we are in the middle of an object literal initialization, we need to update the map
5055         private PropertyMap objectLiteralMap;
5056         // Object literal stack depth for object literal - not necessarly top if property is a tree
5057         private int objectLiteralStackDepth = -1;
5058         // The line number at the continuation point
5059         private int lineNumber;
5060         // The active catch label, in case the continuation point is in a try/catch block
5061         private Label catchLabel;
5062         // The number of scopes that need to be popped before control is transferred to the catch label.
5063         private int exceptionScopePops;
5064 
5065         ContinuationInfo() {
5066             this.handlerLabel = new Label("continuation_handler");
5067         }
5068 
5069         Label getHandlerLabel() {
5070             return handlerLabel;
5071         }
5072 
5073         boolean hasTargetLabel() {
5074             return targetLabel != null;
5075         }
5076 
5077         Label getTargetLabel() {
5078             return targetLabel;
5079         }
5080 
5081         void setTargetLabel(final Label targetLabel) {
5082             this.targetLabel = targetLabel;
5083         }
5084 
5085         int[] getStackStoreSpec() {
5086             return stackStoreSpec.clone();
5087         }
5088 
5089         void setStackStoreSpec(final int[] stackStoreSpec) {
5090             this.stackStoreSpec = stackStoreSpec;
5091         }
5092 
5093         Type[] getStackTypes() {
5094             return stackTypes.clone();
5095         }
5096 
5097         void setStackTypes(final Type[] stackTypes) {
5098             this.stackTypes = stackTypes;
5099         }
5100 
5101         Type getReturnValueType() {
5102             return returnValueType;
5103         }
5104 
5105         void setReturnValueType(final Type returnValueType) {
5106             this.returnValueType = returnValueType;
5107         }
5108 
5109         int getObjectLiteralStackDepth() {
5110             return objectLiteralStackDepth;
5111         }
5112 
5113         void setObjectLiteralStackDepth(final int objectLiteralStackDepth) {
5114             this.objectLiteralStackDepth = objectLiteralStackDepth;
5115         }
5116 
5117         PropertyMap getObjectLiteralMap() {
5118             return objectLiteralMap;
5119         }
5120 
5121         void setObjectLiteralMap(final PropertyMap objectLiteralMap) {
5122             this.objectLiteralMap = objectLiteralMap;
5123         }
5124 
5125         @Override
5126         public String toString() {
5127              return "[localVariableTypes=" + targetLabel.getStack().getLocalVariableTypesCopy() + ", stackStoreSpec=" +
5128                      Arrays.toString(stackStoreSpec) + ", returnValueType=" + returnValueType + "]";
5129         }
5130     }
5131 
5132     private ContinuationInfo getContinuationInfo() {
5133         return fnIdToContinuationInfo.get(lc.getCurrentFunction().getId());
5134     }
5135 
5136     private void generateContinuationHandler() {
5137         if (!isRestOf()) {
5138             return;
5139         }
5140 
5141         final ContinuationInfo ci = getContinuationInfo();
5142         method.label(ci.getHandlerLabel());
5143 
5144         // There should never be an exception thrown from the continuation handler, but in case there is (meaning,
5145         // Nashorn has a bug), then line number 0 will be an indication of where it came from (line numbers are Uint16).
5146         method.lineNumber(0);
5147 
5148         final Label.Stack stack = ci.getTargetLabel().getStack();
5149         final List<Type> lvarTypes = stack.getLocalVariableTypesCopy();
5150         final BitSet symbolBoundary = stack.getSymbolBoundaryCopy();
5151         final int lvarCount = ci.lvarCount;
5152 
5153         final Type rewriteExceptionType = Type.typeFor(RewriteException.class);
5154         // Store the RewriteException into an unused local variable slot.
5155         method.load(rewriteExceptionType, 0);
5156         method.storeTemp(rewriteExceptionType, lvarCount);
5157         // Get local variable array
5158         method.load(rewriteExceptionType, 0);
5159         method.invoke(RewriteException.GET_BYTECODE_SLOTS);
5160         // Store local variables. Note that deoptimization might introduce new value types for existing local variables,
5161         // so we must use both liveLocals and symbolBoundary, as in some cases (when the continuation is inside of a try
5162         // block) we need to store the incoming value into multiple slots. The optimism exception handlers will have
5163         // exactly one array element for every symbol that uses bytecode storage. If in the originating method the value
5164         // was undefined, there will be an explicit Undefined value in the array.
5165         int arrayIndex = 0;
5166         for(int lvarIndex = 0; lvarIndex < lvarCount;) {
5167             final Type lvarType = lvarTypes.get(lvarIndex);
5168             if(!lvarType.isUnknown()) {
5169                 method.dup();
5170                 method.load(arrayIndex).arrayload();
5171                 final Class<?> typeClass = lvarType.getTypeClass();
5172                 // Deoptimization in array initializers can cause arrays to undergo component type widening
5173                 if(typeClass == long[].class) {
5174                     method.load(rewriteExceptionType, lvarCount);
5175                     method.invoke(RewriteException.TO_LONG_ARRAY);
5176                 } else if(typeClass == double[].class) {
5177                     method.load(rewriteExceptionType, lvarCount);
5178                     method.invoke(RewriteException.TO_DOUBLE_ARRAY);
5179                 } else if(typeClass == Object[].class) {
5180                     method.load(rewriteExceptionType, lvarCount);
5181                     method.invoke(RewriteException.TO_OBJECT_ARRAY);
5182                 } else {
5183                     if(!(typeClass.isPrimitive() || typeClass == Object.class)) {
5184                         // NOTE: this can only happen with dead stores. E.g. for the program "1; []; f();" in which the
5185                         // call to f() will deoptimize the call site, but it'll expect :return to have the type
5186                         // NativeArray. However, in the more optimal version, :return's only live type is int, therefore
5187                         // "{O}:return = []" is a dead store, and the variable will be sent into the continuation as
5188                         // Undefined, however NativeArray can't hold Undefined instance.
5189                         method.loadType(Type.getInternalName(typeClass));
5190                         method.invoke(RewriteException.INSTANCE_OR_NULL);
5191                     }
5192                     method.convert(lvarType);
5193                 }
5194                 method.storeHidden(lvarType, lvarIndex, false);
5195             }
5196             final int nextLvarIndex = lvarIndex + lvarType.getSlots();
5197             if(symbolBoundary.get(nextLvarIndex - 1)) {
5198                 ++arrayIndex;
5199             }
5200             lvarIndex = nextLvarIndex;
5201         }
5202         if (AssertsEnabled.assertsEnabled()) {
5203             method.load(arrayIndex);
5204             method.invoke(RewriteException.ASSERT_ARRAY_LENGTH);
5205         } else {
5206             method.pop();
5207         }
5208 
5209         final int[]   stackStoreSpec = ci.getStackStoreSpec();
5210         final Type[]  stackTypes     = ci.getStackTypes();
5211         final boolean isStackEmpty   = stackStoreSpec.length == 0;
5212         boolean replacedObjectLiteralMap = false;
5213         if(!isStackEmpty) {
5214             // Load arguments on the stack
5215             final int objectLiteralStackDepth = ci.getObjectLiteralStackDepth();
5216             for(int i = 0; i < stackStoreSpec.length; ++i) {
5217                 final int slot = stackStoreSpec[i];
5218                 method.load(lvarTypes.get(slot), slot);
5219                 method.convert(stackTypes[i]);
5220                 // stack: s0=object literal being initialized
5221                 // change map of s0 so that the property we are initilizing when we failed
5222                 // is now ci.returnValueType
5223                 if (i == objectLiteralStackDepth) {
5224                     method.dup();
5225                     assert ci.getObjectLiteralMap() != null;
5226                     assert ScriptObject.class.isAssignableFrom(method.peekType().getTypeClass()) : method.peekType().getTypeClass() + " is not a script object";
5227                     loadConstant(ci.getObjectLiteralMap());
5228                     method.invoke(ScriptObject.SET_MAP);
5229                     replacedObjectLiteralMap = true;
5230                 }
5231             }
5232         }
5233         // Must have emitted the code for replacing the map of an object literal if we have a set object literal stack depth
5234         assert ci.getObjectLiteralStackDepth() == -1 || replacedObjectLiteralMap;
5235         // Load RewriteException back.
5236         method.load(rewriteExceptionType, lvarCount);
5237         // Get rid of the stored reference
5238         method.loadNull();
5239         method.storeHidden(Type.OBJECT, lvarCount);
5240         // Mark it dead
5241         method.markDeadSlots(lvarCount, Type.OBJECT.getSlots());
5242 
5243         // Load return value on the stack
5244         method.invoke(RewriteException.GET_RETURN_VALUE);
5245 
5246         final Type returnValueType = ci.getReturnValueType();
5247 
5248         // Set up an exception handler for primitive type conversion of return value if needed
5249         boolean needsCatch = false;
5250         final Label targetCatchLabel = ci.catchLabel;
5251         Label _try = null;
5252         if(returnValueType.isPrimitive()) {
5253             // If the conversion throws an exception, we want to report the line number of the continuation point.
5254             method.lineNumber(ci.lineNumber);
5255 
5256             if(targetCatchLabel != METHOD_BOUNDARY) {
5257                 _try = new Label("");
5258                 method.label(_try);
5259                 needsCatch = true;
5260             }
5261         }
5262 
5263         // Convert return value
5264         method.convert(returnValueType);
5265 
5266         final int scopePopCount = needsCatch ? ci.exceptionScopePops : 0;
5267 
5268         // Declare a try/catch for the conversion. If no scopes need to be popped until the target catch block, just
5269         // jump into it. Otherwise, we'll need to create a scope-popping catch block below.
5270         final Label catchLabel = scopePopCount > 0 ? new Label("") : targetCatchLabel;
5271         if(needsCatch) {
5272             final Label _end_try = new Label("");
5273             method.label(_end_try);
5274             method._try(_try, _end_try, catchLabel);
5275         }
5276 
5277         // Jump to continuation point
5278         method._goto(ci.getTargetLabel());
5279 
5280         // Make a scope-popping exception delegate if needed
5281         if(catchLabel != targetCatchLabel) {
5282             method.lineNumber(0);
5283             assert scopePopCount > 0;
5284             method._catch(catchLabel);
5285             popScopes(scopePopCount);
5286             method.uncheckedGoto(targetCatchLabel);
5287         }
5288     }
5289 }
--- EOF ---