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.runtime.linker.NashornCallSiteDescriptor.CALLSITE_OPTIMISTIC;
29
30 import java.util.Arrays;
31 import java.util.EnumSet;
32 import jdk.nashorn.internal.codegen.types.Type;
33 import jdk.nashorn.internal.ir.Symbol;
34 import jdk.nashorn.internal.runtime.ScriptObject;
35
36 /**
37 * A scope call or get operation that can be shared by several callsites. This generates a static
38 * method that wraps the invokedynamic instructions to get or call scope variables.
39 * The rationale for this is that initial linking of invokedynamic callsites is expensive,
40 * so by sharing them we can reduce startup overhead and allow very large scripts to run that otherwise wouldn't.
41 *
42 * <p>Static methods generated by this class expect two parameters in addition to the parameters of the
43 * function call: The current scope object and the depth of the target scope relative to the scope argument
44 * for when this is known at compile-time (fast-scope access).</p>
45 *
46 * <p>The second argument may be -1 for non-fast-scope symbols, in which case the scope chain is checked
47 * for each call. This may cause callsite invalidation when the shared method is used from different
48 * scopes, but such sharing of non-fast scope calls may still be necessary for very large scripts.</p>
49 *
50 * <p>Scope calls must not be shared between normal callsites and callsites contained in a <tt>with</tt>
51 * statement as this condition is not handled by current guards and will cause a runtime error.</p>
52 */
53 class SharedScopeCall {
54
55 /** Threshold for using shared scope calls with fast scope access. */
56 public static final int FAST_SCOPE_CALL_THRESHOLD = 4;
57 /** Threshold for using shared scope calls with slow scope access. */
58 public static final int SLOW_SCOPE_CALL_THRESHOLD = 500;
59 /** Threshold for using shared scope gets with fast scope access. */
60 public static final int FAST_SCOPE_GET_THRESHOLD = 200;
61
62 final Type valueType;
63 final Symbol symbol;
64 final Type returnType;
65 final Type[] paramTypes;
66 final int flags;
67 final boolean isCall;
68 private CompileUnit compileUnit;
69 private String methodName;
70 private String staticSignature;
71
72 /**
73 * Constructor.
74 *
75 * @param symbol the symbol
76 * @param valueType the type of the value
77 * @param returnType the return type
78 * @param paramTypes the function parameter types
79 * @param flags the callsite flags
80 */
81 SharedScopeCall(final Symbol symbol, final Type valueType, final Type returnType, final Type[] paramTypes, final int flags) {
82 this.symbol = symbol;
83 this.valueType = valueType;
84 this.returnType = returnType;
85 this.paramTypes = paramTypes;
86 assert (flags & CALLSITE_OPTIMISTIC) == 0;
87 this.flags = flags;
88 // If paramTypes is not null this is a call, otherwise it's just a get.
89 this.isCall = paramTypes != null;
90 }
91
92 @Override
93 public int hashCode() {
94 return symbol.hashCode() ^ returnType.hashCode() ^ Arrays.hashCode(paramTypes) ^ flags;
95 }
96
97 @Override
98 public boolean equals(final Object obj) {
99 if (obj instanceof SharedScopeCall) {
100 final SharedScopeCall c = (SharedScopeCall) obj;
101 return symbol.equals(c.symbol)
102 && flags == c.flags
103 && returnType.equals(c.returnType)
104 && Arrays.equals(paramTypes, c.paramTypes);
105 }
106 return false;
107 }
108
109 /**
110 * Set the compile unit and method name.
111 * @param compileUnit the compile unit
112 * @param methodName the method name
113 */
114 protected void setClassAndName(final CompileUnit compileUnit, final String methodName) {
115 this.compileUnit = compileUnit;
116 this.methodName = methodName;
117 }
118
119 /**
120 * Generate the invoke instruction for this shared scope call.
121 * @param method the method emitter
122 * @return the method emitter
123 */
124 public MethodEmitter generateInvoke(final MethodEmitter method) {
125 return method.invokestatic(compileUnit.getUnitClassName(), methodName, getStaticSignature());
126 }
127
128 /**
129 * Generate the method that implements the scope get or call.
130 */
131 protected void generateScopeCall() {
132 final ClassEmitter classEmitter = compileUnit.getClassEmitter();
133 final EnumSet<ClassEmitter.Flag> methodFlags = EnumSet.of(ClassEmitter.Flag.STATIC);
134
135 // This method expects two fixed parameters in addition to any parameters that may be
136 // passed on to the function: A ScriptObject representing the caller's current scope object,
137 // and an int specifying the distance to the target scope containing the symbol we want to
138 // access, or -1 if this is not known at compile time (e.g. because of a "with" or "eval").
139
140 final MethodEmitter method = classEmitter.method(methodFlags, methodName, getStaticSignature());
141 method.begin();
142
143 // Load correct scope by calling getProto() on the scope argument as often as specified
144 // by the second argument.
145 final Label parentLoopStart = new Label("parent_loop_start");
146 final Label parentLoopDone = new Label("parent_loop_done");
147 method.load(Type.OBJECT, 0);
148 method.label(parentLoopStart);
149 method.load(Type.INT, 1);
150 method.iinc(1, -1);
151 method.ifle(parentLoopDone);
152 method.invoke(ScriptObject.GET_PROTO);
153 method._goto(parentLoopStart);
154 method.label(parentLoopDone);
155
156 assert !isCall || valueType.isObject(); // Callables are always objects
157 // If flags are optimistic, but we're doing a call, remove optimistic flags from the getter, as they obviously
158 // only apply to the call.
159 method.dynamicGet(valueType, symbol.getName(), isCall ? CodeGenerator.nonOptimisticFlags(flags) : flags, isCall);
160
161 // If this is a get we're done, otherwise call the value as function.
162 if (isCall) {
163 method.convert(Type.OBJECT);
164 // ScriptFunction will see CALLSITE_SCOPE and will bind scope accordingly.
165 method.loadUndefined(Type.OBJECT);
166 int slot = 2;
167 for (final Type type : paramTypes) {
168 method.load(type, slot);
169 slot += type.getSlots();
170 }
171 // Shared scope calls disabled in optimistic world. TODO is this right?
172 method.dynamicCall(returnType, 2 + paramTypes.length, flags);
173 }
174
175 method._return(returnType);
176 method.end();
177 }
178
179 private String getStaticSignature() {
180 if (staticSignature == null) {
181 if (paramTypes == null) {
182 staticSignature = Type.getMethodDescriptor(returnType, Type.typeFor(ScriptObject.class), Type.INT);
183 } else {
184 final Type[] params = new Type[paramTypes.length + 2];
185 params[0] = Type.typeFor(ScriptObject.class);
186 params[1] = Type.INT;
187 System.arraycopy(paramTypes, 0, params, 2, paramTypes.length);
188 staticSignature = Type.getMethodDescriptor(returnType, params);
189 }
190 }
191 return staticSignature;
192 }
193
194 @Override
195 public String toString() {
196 return methodName + " " + staticSignature;
197 }
198
199 }