SharedScopeCall.java revision 1141:7c1cff3cae2e
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 26package jdk.nashorn.internal.codegen; 27 28import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_OPTIMISTIC; 29 30import java.util.Arrays; 31import java.util.EnumSet; 32import jdk.nashorn.internal.codegen.types.Type; 33import jdk.nashorn.internal.ir.Symbol; 34import 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 */ 53class 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, false); 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} 200