bytecode/PutByIdStatus.cpp

   1 /*
   2  * Copyright (C) 2012 Apple Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #include "config.h"
  27 #include "PutByIdStatus.h"
  28
  29 #include "CodeBlock.h"
  30 #include "LLIntData.h"
  31 #include "LowLevelInterpreter.h"
  32 #include "Operations.h"
  33 #include "Structure.h"
  34 #include "StructureChain.h"
  35
  36 namespace JSC {
  37
  38 PutByIdStatus PutByIdStatus::computeFromLLInt(CodeBlock* profiledBlock, unsigned bytecodeIndex, Identifier& ident)
  39 {
  40     UNUSED_PARAM(profiledBlock);
  41     UNUSED_PARAM(bytecodeIndex);
  42     UNUSED_PARAM(ident);
  43 #if ENABLE(LLINT)
  44     Instruction* instruction = profiledBlock->instructions().begin() + bytecodeIndex;
  45
  46     Structure* structure = instruction[4].u.structure.get();
  47     if (!structure)
  48         return PutByIdStatus(NoInformation, 0, 0, 0, invalidOffset);
  49
  50     if (instruction[0].u.opcode == LLInt::getOpcode(llint_op_put_by_id)
  51         || instruction[0].u.opcode == LLInt::getOpcode(llint_op_put_by_id_out_of_line)) {
  52         PropertyOffset offset = structure->get(*profiledBlock->vm(), ident);
  53         if (!isValidOffset(offset))
  54             return PutByIdStatus(NoInformation, 0, 0, 0, invalidOffset);
  55
  56         return PutByIdStatus(SimpleReplace, structure, 0, 0, offset);
  57     }
  58
  59     ASSERT(structure->transitionWatchpointSetHasBeenInvalidated());
  60
  61     ASSERT(instruction[0].u.opcode == LLInt::getOpcode(llint_op_put_by_id_transition_direct)
  62            || instruction[0].u.opcode == LLInt::getOpcode(llint_op_put_by_id_transition_normal)
  63            || instruction[0].u.opcode == LLInt::getOpcode(llint_op_put_by_id_transition_direct_out_of_line)
  64            || instruction[0].u.opcode == LLInt::getOpcode(llint_op_put_by_id_transition_normal_out_of_line));
  65
  66     Structure* newStructure = instruction[6].u.structure.get();
  67     StructureChain* chain = instruction[7].u.structureChain.get();
  68     ASSERT(newStructure);
  69     ASSERT(chain);
  70
  71     PropertyOffset offset = newStructure->get(*profiledBlock->vm(), ident);
  72     if (!isValidOffset(offset))
  73         return PutByIdStatus(NoInformation, 0, 0, 0, invalidOffset);
  74
  75     return PutByIdStatus(SimpleTransition, structure, newStructure, chain, offset);
  76 #else
  77     return PutByIdStatus(NoInformation, 0, 0, 0, invalidOffset);
  78 #endif
  79 }
  80
  81 PutByIdStatus PutByIdStatus::computeFor(CodeBlock* profiledBlock, unsigned bytecodeIndex, Identifier& ident)
  82 {
  83     UNUSED_PARAM(profiledBlock);
  84     UNUSED_PARAM(bytecodeIndex);
  85     UNUSED_PARAM(ident);
  86 #if ENABLE(JIT) && ENABLE(VALUE_PROFILER)
  87     if (!profiledBlock->numberOfStructureStubInfos())
  88         return computeFromLLInt(profiledBlock, bytecodeIndex, ident);
  89
  90     if (profiledBlock->likelyToTakeSlowCase(bytecodeIndex))
  91         return PutByIdStatus(TakesSlowPath, 0, 0, 0, invalidOffset);
  92
  93     StructureStubInfo& stubInfo = profiledBlock->getStubInfo(bytecodeIndex);
  94     if (!stubInfo.seen)
  95         return computeFromLLInt(profiledBlock, bytecodeIndex, ident);
  96
  97     if (stubInfo.resetByGC)
  98         return PutByIdStatus(TakesSlowPath, 0, 0, 0, invalidOffset);
  99
 100     switch (stubInfo.accessType) {
 101     case access_unset:
 102         // If the JIT saw it but didn't optimize it, then assume that this takes slow path.
 103         return PutByIdStatus(TakesSlowPath, 0, 0, 0, invalidOffset);
 104
 105     case access_put_by_id_replace: {
 106         PropertyOffset offset = stubInfo.u.putByIdReplace.baseObjectStructure->get(
 107             *profiledBlock->vm(), ident);
 108         if (isValidOffset(offset)) {
 109             return PutByIdStatus(
 110                 SimpleReplace,
 111                 stubInfo.u.putByIdReplace.baseObjectStructure.get(),
 112                 0, 0,
 113                 offset);
 114         }
 115         return PutByIdStatus(TakesSlowPath, 0, 0, 0, invalidOffset);
 116     }
 117
 118     case access_put_by_id_transition_normal:
 119     case access_put_by_id_transition_direct: {
 120         ASSERT(stubInfo.u.putByIdTransition.previousStructure->transitionWatchpointSetHasBeenInvalidated());
 121         PropertyOffset offset = stubInfo.u.putByIdTransition.structure->get(
 122             *profiledBlock->vm(), ident);
 123         if (isValidOffset(offset)) {
 124             return PutByIdStatus(
 125                 SimpleTransition,
 126                 stubInfo.u.putByIdTransition.previousStructure.get(),
 127                 stubInfo.u.putByIdTransition.structure.get(),
 128                 stubInfo.u.putByIdTransition.chain.get(),
 129                 offset);
 130         }
 131         return PutByIdStatus(TakesSlowPath, 0, 0, 0, invalidOffset);
 132     }
 133
 134     default:
 135         return PutByIdStatus(TakesSlowPath, 0, 0, 0, invalidOffset);
 136     }
 137 #else // ENABLE(JIT)
 138     return PutByIdStatus(NoInformation, 0, 0, 0, invalidOffset);
 139 #endif // ENABLE(JIT)
 140 }
 141
 142 PutByIdStatus PutByIdStatus::computeFor(VM& vm, JSGlobalObject* globalObject, Structure* structure, Identifier& ident, bool isDirect)
 143 {
 144     if (PropertyName(ident).asIndex() != PropertyName::NotAnIndex)
 145         return PutByIdStatus(TakesSlowPath);
 146
 147     if (structure->typeInfo().overridesGetOwnPropertySlot())
 148         return PutByIdStatus(TakesSlowPath);
 149
 150     if (!structure->propertyAccessesAreCacheable())
 151         return PutByIdStatus(TakesSlowPath);
 152
 153     unsigned attributes;
 154     JSCell* specificValue;
 155     PropertyOffset offset = structure->get(vm, ident, attributes, specificValue);
 156     if (isValidOffset(offset)) {
 157         if (attributes & (Accessor | ReadOnly))
 158             return PutByIdStatus(TakesSlowPath);
 159         if (specificValue) {
 160             // We need the PutById slow path to verify that we're storing the right value into
 161             // the specialized slot.
 162             return PutByIdStatus(TakesSlowPath);
 163         }
 164         return PutByIdStatus(SimpleReplace, structure, 0, 0, offset);
 165     }
 166
 167     // Our hypothesis is that we're doing a transition. Before we prove that this is really
 168     // true, we want to do some sanity checks.
 169
 170     // Don't cache put transitions on dictionaries.
 171     if (structure->isDictionary())
 172         return PutByIdStatus(TakesSlowPath);
 173
 174     // If the structure corresponds to something that isn't an object, then give up, since
 175     // we don't want to be adding properties to strings.
 176     if (structure->typeInfo().type() == StringType)
 177         return PutByIdStatus(TakesSlowPath);
 178
 179     if (!isDirect) {
 180         // If the prototype chain has setters or read-only properties, then give up.
 181         if (structure->prototypeChainMayInterceptStoreTo(vm, ident))
 182             return PutByIdStatus(TakesSlowPath);
 183
 184         // If the prototype chain hasn't been normalized (i.e. there are proxies or dictionaries)
 185         // then give up. The dictionary case would only happen if this structure has not been
 186         // used in an optimized put_by_id transition. And really the only reason why we would
 187         // bail here is that I don't really feel like having the optimizing JIT go and flatten
 188         // dictionaries if we have evidence to suggest that those objects were never used as
 189         // prototypes in a cacheable prototype access - i.e. there's a good chance that some of
 190         // the other checks below will fail.
 191         if (!isPrototypeChainNormalized(globalObject, structure))
 192             return PutByIdStatus(TakesSlowPath);
 193     }
 194
 195     // We only optimize if there is already a structure that the transition is cached to.
 196     // Among other things, this allows us to guard against a transition with a specific
 197     // value.
 198     //
 199     // - If we're storing a value that could be specific: this would only be a problem if
 200     //   the existing transition did have a specific value already, since if it didn't,
 201     //   then we would behave "as if" we were not storing a specific value. If it did
 202     //   have a specific value, then we'll know - the fact that we pass 0 for
 203     //   specificValue will tell us.
 204     //
 205     // - If we're not storing a value that could be specific: again, this would only be a
 206     //   problem if the existing transition did have a specific value, which we check for
 207     //   by passing 0 for the specificValue.
 208     Structure* transition = Structure::addPropertyTransitionToExistingStructure(structure, ident, 0, 0, offset);
 209     if (!transition)
 210         return PutByIdStatus(TakesSlowPath); // This occurs in bizarre cases only. See above.
 211     ASSERT(!transition->transitionDidInvolveSpecificValue());
 212     ASSERT(isValidOffset(offset));
 213
 214     return PutByIdStatus(
 215         SimpleTransition, structure, transition,
 216         structure->prototypeChain(vm, globalObject), offset);
 217 }
 218
 219 } // namespace JSC
 220