[apple/javascriptcore.git] / bytecode / GetByIdStatus.cpp

/*
 * Copyright (C) 2012 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 */

#include "config.h"
#include "GetByIdStatus.h"

#include "CodeBlock.h"
#include "JSScope.h"
#include "LLIntData.h"
#include "LowLevelInterpreter.h"
#include "Operations.h"

namespace JSC {

GetByIdStatus GetByIdStatus::computeFromLLInt(CodeBlock* profiledBlock, unsigned bytecodeIndex, Identifier& ident)
{
    UNUSED_PARAM(profiledBlock);
    UNUSED_PARAM(bytecodeIndex);
    UNUSED_PARAM(ident);
#if ENABLE(LLINT)
    Instruction* instruction = profiledBlock->instructions().begin() + bytecodeIndex;
    
    if (instruction[0].u.opcode == LLInt::getOpcode(llint_op_get_array_length))
        return GetByIdStatus(NoInformation, false);

    Structure* structure = instruction[4].u.structure.get();
    if (!structure)
        return GetByIdStatus(NoInformation, false);
    
    unsigned attributesIgnored;
    JSCell* specificValue;
    PropertyOffset offset = structure->get(
        *profiledBlock->vm(), ident, attributesIgnored, specificValue);
    if (structure->isDictionary())
        specificValue = 0;
    if (!isValidOffset(offset))
        return GetByIdStatus(NoInformation, false);
    
    return GetByIdStatus(Simple, false, StructureSet(structure), offset, specificValue);
#else
    return GetByIdStatus(NoInformation, false);
#endif
}

void GetByIdStatus::computeForChain(GetByIdStatus& result, CodeBlock* profiledBlock, Identifier& ident, Structure* structure)
{
#if ENABLE(JIT) && ENABLE(VALUE_PROFILER)
    // Validate the chain. If the chain is invalid, then currently the best thing
    // we can do is to assume that TakesSlow is true. In the future, it might be
    // worth exploring reifying the structure chain from the structure we've got
    // instead of using the one from the cache, since that will do the right things
    // if the structure chain has changed. But that may be harder, because we may
    // then end up having a different type of access altogether. And it currently
    // does not appear to be worth it to do so -- effectively, the heuristic we
    // have now is that if the structure chain has changed between when it was
    // cached on in the baseline JIT and when the DFG tried to inline the access,
    // then we fall back on a polymorphic access.
    Structure* currentStructure = structure;
    JSObject* currentObject = 0;
    for (unsigned i = 0; i < result.m_chain.size(); ++i) {
        ASSERT(!currentStructure->isDictionary());
        currentObject = asObject(currentStructure->prototypeForLookup(profiledBlock));
        currentStructure = result.m_chain[i];
        if (currentObject->structure() != currentStructure)
            return;
    }
    
    ASSERT(currentObject);
        
    unsigned attributesIgnored;
    JSCell* specificValue;
        
    result.m_offset = currentStructure->get(
        *profiledBlock->vm(), ident, attributesIgnored, specificValue);
    if (currentStructure->isDictionary())
        specificValue = 0;
    if (!isValidOffset(result.m_offset))
        return;
        
    result.m_structureSet.add(structure);
    result.m_specificValue = JSValue(specificValue);
#else
    UNUSED_PARAM(result);
    UNUSED_PARAM(profiledBlock);
    UNUSED_PARAM(ident);
    UNUSED_PARAM(structure);
    UNREACHABLE_FOR_PLATFORM();
#endif
}

GetByIdStatus GetByIdStatus::computeFor(CodeBlock* profiledBlock, unsigned bytecodeIndex, Identifier& ident)
{
    UNUSED_PARAM(profiledBlock);
    UNUSED_PARAM(bytecodeIndex);
    UNUSED_PARAM(ident);
#if ENABLE(JIT) && ENABLE(VALUE_PROFILER)
    if (!profiledBlock->numberOfStructureStubInfos())
        return computeFromLLInt(profiledBlock, bytecodeIndex, ident);
    
    // First check if it makes either calls, in which case we want to be super careful, or
    // if it's not set at all, in which case we punt.
    StructureStubInfo& stubInfo = profiledBlock->getStubInfo(bytecodeIndex);
    if (!stubInfo.seen)
        return computeFromLLInt(profiledBlock, bytecodeIndex, ident);
    
    if (stubInfo.resetByGC)
        return GetByIdStatus(TakesSlowPath, true);

    PolymorphicAccessStructureList* list;
    int listSize;
    switch (stubInfo.accessType) {
    case access_get_by_id_self_list:
        list = stubInfo.u.getByIdSelfList.structureList;
        listSize = stubInfo.u.getByIdSelfList.listSize;
        break;
    case access_get_by_id_proto_list:
        list = stubInfo.u.getByIdProtoList.structureList;
        listSize = stubInfo.u.getByIdProtoList.listSize;
        break;
    default:
        list = 0;
        listSize = 0;
        break;
    }
    for (int i = 0; i < listSize; ++i) {
        if (!list->list[i].isDirect)
            return GetByIdStatus(MakesCalls, true);
    }
    
    // Next check if it takes slow case, in which case we want to be kind of careful.
    if (profiledBlock->likelyToTakeSlowCase(bytecodeIndex))
        return GetByIdStatus(TakesSlowPath, true);
    
    // Finally figure out if we can derive an access strategy.
    GetByIdStatus result;
    result.m_wasSeenInJIT = true; // This is interesting for bytecode dumping only.
    switch (stubInfo.accessType) {
    case access_unset:
        return computeFromLLInt(profiledBlock, bytecodeIndex, ident);
        
    case access_get_by_id_self: {
        Structure* structure = stubInfo.u.getByIdSelf.baseObjectStructure.get();
        unsigned attributesIgnored;
        JSCell* specificValue;
        result.m_offset = structure->get(
            *profiledBlock->vm(), ident, attributesIgnored, specificValue);
        if (structure->isDictionary())
            specificValue = 0;
        
        if (isValidOffset(result.m_offset)) {
            result.m_structureSet.add(structure);
            result.m_specificValue = JSValue(specificValue);
        }
        
        if (isValidOffset(result.m_offset))
            ASSERT(result.m_structureSet.size());
        break;
    }
        
    case access_get_by_id_self_list: {
        for (int i = 0; i < listSize; ++i) {
            ASSERT(list->list[i].isDirect);
            
            Structure* structure = list->list[i].base.get();
            if (result.m_structureSet.contains(structure))
                continue;
            
            unsigned attributesIgnored;
            JSCell* specificValue;
            PropertyOffset myOffset = structure->get(
                *profiledBlock->vm(), ident, attributesIgnored, specificValue);
            if (structure->isDictionary())
                specificValue = 0;
            
            if (!isValidOffset(myOffset)) {
                result.m_offset = invalidOffset;
                break;
            }
                    
            if (!i) {
                result.m_offset = myOffset;
                result.m_specificValue = JSValue(specificValue);
            } else if (result.m_offset != myOffset) {
                result.m_offset = invalidOffset;
                break;
            } else if (result.m_specificValue != JSValue(specificValue))
                result.m_specificValue = JSValue();
            
            result.m_structureSet.add(structure);
        }
                    
        if (isValidOffset(result.m_offset))
            ASSERT(result.m_structureSet.size());
        break;
    }
        
    case access_get_by_id_proto: {
        if (!stubInfo.u.getByIdProto.isDirect)
            return GetByIdStatus(MakesCalls, true);
        result.m_chain.append(stubInfo.u.getByIdProto.prototypeStructure.get());
        computeForChain(
            result, profiledBlock, ident,
            stubInfo.u.getByIdProto.baseObjectStructure.get());
        break;
    }
        
    case access_get_by_id_chain: {
        if (!stubInfo.u.getByIdChain.isDirect)
            return GetByIdStatus(MakesCalls, true);
        for (unsigned i = 0; i < stubInfo.u.getByIdChain.count; ++i)
            result.m_chain.append(stubInfo.u.getByIdChain.chain->head()[i].get());
        computeForChain(
            result, profiledBlock, ident,
            stubInfo.u.getByIdChain.baseObjectStructure.get());
        break;
    }
        
    default:
        ASSERT(!isValidOffset(result.m_offset));
        break;
    }
    
    if (!isValidOffset(result.m_offset)) {
        result.m_state = TakesSlowPath;
        result.m_structureSet.clear();
        result.m_chain.clear();
        result.m_specificValue = JSValue();
    } else
        result.m_state = Simple;
    
    return result;
#else // ENABLE(JIT)
    return GetByIdStatus(NoInformation, false);
#endif // ENABLE(JIT)
}

GetByIdStatus GetByIdStatus::computeFor(VM& vm, Structure* structure, Identifier& ident)
{
    // For now we only handle the super simple self access case. We could handle the
    // prototype case in the future.
    
    if (PropertyName(ident).asIndex() != PropertyName::NotAnIndex)
        return GetByIdStatus(TakesSlowPath);
    
    if (structure->typeInfo().overridesGetOwnPropertySlot())
        return GetByIdStatus(TakesSlowPath);
    
    if (!structure->propertyAccessesAreCacheable())
        return GetByIdStatus(TakesSlowPath);
    
    GetByIdStatus result;
    result.m_wasSeenInJIT = false; // To my knowledge nobody that uses computeFor(VM&, Structure*, Identifier&) reads this field, but I might as well be honest: no, it wasn't seen in the JIT, since I computed it statically.
    unsigned attributes;
    JSCell* specificValue;
    result.m_offset = structure->get(vm, ident, attributes, specificValue);
    if (!isValidOffset(result.m_offset))
        return GetByIdStatus(TakesSlowPath); // It's probably a prototype lookup. Give up on life for now, even though we could totally be way smarter about it.
    if (attributes & Accessor)
        return GetByIdStatus(MakesCalls);
    if (structure->isDictionary())
        specificValue = 0;
    result.m_structureSet.add(structure);
    result.m_specificValue = JSValue(specificValue);
    return result;
}

} // namespace JSC
Commit	Line	Data
6fe7ccc8 A	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 "GetByIdStatus.h"
	28
	29	#include "CodeBlock.h"
93a37866 A	30	#include "JSScope.h"
93a37866 A	31	#include "LLIntData.h"
6fe7ccc8	32	#include "LowLevelInterpreter.h"
93a37866	33	#include "Operations.h"
6fe7ccc8 A	34
	35	namespace JSC {
	36
	37	GetByIdStatus GetByIdStatus::computeFromLLInt(CodeBlock* profiledBlock, unsigned bytecodeIndex, Identifier& ident)
	38	{
	39	UNUSED_PARAM(profiledBlock);
	40	UNUSED_PARAM(bytecodeIndex);
	41	UNUSED_PARAM(ident);
	42	#if ENABLE(LLINT)
	43	Instruction* instruction = profiledBlock->instructions().begin() + bytecodeIndex;
	44
93a37866 A	45	if (instruction[0].u.opcode == LLInt::getOpcode(llint_op_get_array_length))
93a37866 A	46	return GetByIdStatus(NoInformation, false);
6fe7ccc8 A	47
	48	Structure* structure = instruction[4].u.structure.get();
	49	if (!structure)
93a37866	50	return GetByIdStatus(NoInformation, false);
6fe7ccc8	51
93a37866 A	52	unsigned attributesIgnored;
	53	JSCell* specificValue;
	54	PropertyOffset offset = structure->get(
	55	*profiledBlock->vm(), ident, attributesIgnored, specificValue);
	56	if (structure->isDictionary())
	57	specificValue = 0;
	58	if (!isValidOffset(offset))
	59	return GetByIdStatus(NoInformation, false);
6fe7ccc8	60
93a37866	61	return GetByIdStatus(Simple, false, StructureSet(structure), offset, specificValue);
6fe7ccc8	62	#else
93a37866 A	63	return GetByIdStatus(NoInformation, false);
	64	#endif
	65	}
	66
	67	void GetByIdStatus::computeForChain(GetByIdStatus& result, CodeBlock* profiledBlock, Identifier& ident, Structure* structure)
	68	{
	69	#if ENABLE(JIT) && ENABLE(VALUE_PROFILER)
	70	// Validate the chain. If the chain is invalid, then currently the best thing
	71	// we can do is to assume that TakesSlow is true. In the future, it might be
	72	// worth exploring reifying the structure chain from the structure we've got
	73	// instead of using the one from the cache, since that will do the right things
	74	// if the structure chain has changed. But that may be harder, because we may
	75	// then end up having a different type of access altogether. And it currently
	76	// does not appear to be worth it to do so -- effectively, the heuristic we
	77	// have now is that if the structure chain has changed between when it was
	78	// cached on in the baseline JIT and when the DFG tried to inline the access,
	79	// then we fall back on a polymorphic access.
	80	Structure* currentStructure = structure;
	81	JSObject* currentObject = 0;
	82	for (unsigned i = 0; i < result.m_chain.size(); ++i) {
	83	ASSERT(!currentStructure->isDictionary());
	84	currentObject = asObject(currentStructure->prototypeForLookup(profiledBlock));
	85	currentStructure = result.m_chain[i];
	86	if (currentObject->structure() != currentStructure)
	87	return;
	88	}
	89
	90	ASSERT(currentObject);
	91
	92	unsigned attributesIgnored;
	93	JSCell* specificValue;
	94
	95	result.m_offset = currentStructure->get(
	96	*profiledBlock->vm(), ident, attributesIgnored, specificValue);
	97	if (currentStructure->isDictionary())
	98	specificValue = 0;
	99	if (!isValidOffset(result.m_offset))
	100	return;
	101
	102	result.m_structureSet.add(structure);
	103	result.m_specificValue = JSValue(specificValue);
	104	#else
	105	UNUSED_PARAM(result);
	106	UNUSED_PARAM(profiledBlock);
	107	UNUSED_PARAM(ident);
	108	UNUSED_PARAM(structure);
	109	UNREACHABLE_FOR_PLATFORM();
6fe7ccc8 A	110	#endif
	111	}
	112
	113	GetByIdStatus GetByIdStatus::computeFor(CodeBlock* profiledBlock, unsigned bytecodeIndex, Identifier& ident)
	114	{
	115	UNUSED_PARAM(profiledBlock);
	116	UNUSED_PARAM(bytecodeIndex);
	117	UNUSED_PARAM(ident);
	118	#if ENABLE(JIT) && ENABLE(VALUE_PROFILER)
	119	if (!profiledBlock->numberOfStructureStubInfos())
	120	return computeFromLLInt(profiledBlock, bytecodeIndex, ident);
	121
	122	// First check if it makes either calls, in which case we want to be super careful, or
	123	// if it's not set at all, in which case we punt.
	124	StructureStubInfo& stubInfo = profiledBlock->getStubInfo(bytecodeIndex);
	125	if (!stubInfo.seen)
	126	return computeFromLLInt(profiledBlock, bytecodeIndex, ident);
	127
93a37866 A	128	if (stubInfo.resetByGC)
	129	return GetByIdStatus(TakesSlowPath, true);
	130
6fe7ccc8 A	131	PolymorphicAccessStructureList* list;
	132	int listSize;
	133	switch (stubInfo.accessType) {
	134	case access_get_by_id_self_list:
	135	list = stubInfo.u.getByIdSelfList.structureList;
	136	listSize = stubInfo.u.getByIdSelfList.listSize;
	137	break;
	138	case access_get_by_id_proto_list:
	139	list = stubInfo.u.getByIdProtoList.structureList;
	140	listSize = stubInfo.u.getByIdProtoList.listSize;
	141	break;
	142	default:
	143	list = 0;
	144	listSize = 0;
	145	break;
	146	}
	147	for (int i = 0; i < listSize; ++i) {
	148	if (!list->list[i].isDirect)
93a37866	149	return GetByIdStatus(MakesCalls, true);
6fe7ccc8 A	150	}
	151
	152	// Next check if it takes slow case, in which case we want to be kind of careful.
	153	if (profiledBlock->likelyToTakeSlowCase(bytecodeIndex))
93a37866	154	return GetByIdStatus(TakesSlowPath, true);
6fe7ccc8 A	155
	156	// Finally figure out if we can derive an access strategy.
	157	GetByIdStatus result;
93a37866	158	result.m_wasSeenInJIT = true; // This is interesting for bytecode dumping only.
6fe7ccc8 A	159	switch (stubInfo.accessType) {
	160	case access_unset:
	161	return computeFromLLInt(profiledBlock, bytecodeIndex, ident);
	162
	163	case access_get_by_id_self: {
	164	Structure* structure = stubInfo.u.getByIdSelf.baseObjectStructure.get();
93a37866 A	165	unsigned attributesIgnored;
	166	JSCell* specificValue;
	167	result.m_offset = structure->get(
	168	*profiledBlock->vm(), ident, attributesIgnored, specificValue);
	169	if (structure->isDictionary())
	170	specificValue = 0;
6fe7ccc8	171
93a37866	172	if (isValidOffset(result.m_offset)) {
6fe7ccc8	173	result.m_structureSet.add(structure);
93a37866 A	174	result.m_specificValue = JSValue(specificValue);
93a37866 A	175	}
6fe7ccc8	176
93a37866	177	if (isValidOffset(result.m_offset))
6fe7ccc8 A	178	ASSERT(result.m_structureSet.size());
	179	break;
	180	}
	181
	182	case access_get_by_id_self_list: {
93a37866	183	for (int i = 0; i < listSize; ++i) {
6fe7ccc8 A	184	ASSERT(list->list[i].isDirect);
	185
	186	Structure* structure = list->list[i].base.get();
	187	if (result.m_structureSet.contains(structure))
	188	continue;
	189
93a37866 A	190	unsigned attributesIgnored;
	191	JSCell* specificValue;
	192	PropertyOffset myOffset = structure->get(
	193	*profiledBlock->vm(), ident, attributesIgnored, specificValue);
	194	if (structure->isDictionary())
	195	specificValue = 0;
6fe7ccc8	196
93a37866 A	197	if (!isValidOffset(myOffset)) {
93a37866 A	198	result.m_offset = invalidOffset;
6fe7ccc8 A	199	break;
	200	}
	201
93a37866	202	if (!i) {
6fe7ccc8	203	result.m_offset = myOffset;
93a37866 A	204	result.m_specificValue = JSValue(specificValue);
	205	} else if (result.m_offset != myOffset) {
	206	result.m_offset = invalidOffset;
6fe7ccc8	207	break;
93a37866 A	208	} else if (result.m_specificValue != JSValue(specificValue))
	209	result.m_specificValue = JSValue();
	210
6fe7ccc8 A	211	result.m_structureSet.add(structure);
	212	}
	213
93a37866	214	if (isValidOffset(result.m_offset))
6fe7ccc8 A	215	ASSERT(result.m_structureSet.size());
	216	break;
	217	}
	218
93a37866 A	219	case access_get_by_id_proto: {
	220	if (!stubInfo.u.getByIdProto.isDirect)
	221	return GetByIdStatus(MakesCalls, true);
	222	result.m_chain.append(stubInfo.u.getByIdProto.prototypeStructure.get());
	223	computeForChain(
	224	result, profiledBlock, ident,
	225	stubInfo.u.getByIdProto.baseObjectStructure.get());
	226	break;
	227	}
	228
	229	case access_get_by_id_chain: {
	230	if (!stubInfo.u.getByIdChain.isDirect)
	231	return GetByIdStatus(MakesCalls, true);
	232	for (unsigned i = 0; i < stubInfo.u.getByIdChain.count; ++i)
	233	result.m_chain.append(stubInfo.u.getByIdChain.chain->head()[i].get());
	234	computeForChain(
	235	result, profiledBlock, ident,
	236	stubInfo.u.getByIdChain.baseObjectStructure.get());
	237	break;
	238	}
	239
6fe7ccc8	240	default:
93a37866	241	ASSERT(!isValidOffset(result.m_offset));
6fe7ccc8 A	242	break;
	243	}
	244
93a37866	245	if (!isValidOffset(result.m_offset)) {
6fe7ccc8 A	246	result.m_state = TakesSlowPath;
6fe7ccc8 A	247	result.m_structureSet.clear();
93a37866 A	248	result.m_chain.clear();
93a37866 A	249	result.m_specificValue = JSValue();
6fe7ccc8	250	} else
93a37866	251	result.m_state = Simple;
6fe7ccc8 A	252
	253	return result;
	254	#else // ENABLE(JIT)
93a37866	255	return GetByIdStatus(NoInformation, false);
6fe7ccc8 A	256	#endif // ENABLE(JIT)
	257	}
	258
93a37866 A	259	GetByIdStatus GetByIdStatus::computeFor(VM& vm, Structure* structure, Identifier& ident)
	260	{
	261	// For now we only handle the super simple self access case. We could handle the
	262	// prototype case in the future.
	263
	264	if (PropertyName(ident).asIndex() != PropertyName::NotAnIndex)
	265	return GetByIdStatus(TakesSlowPath);
	266
	267	if (structure->typeInfo().overridesGetOwnPropertySlot())
	268	return GetByIdStatus(TakesSlowPath);
	269
	270	if (!structure->propertyAccessesAreCacheable())
	271	return GetByIdStatus(TakesSlowPath);
	272
	273	GetByIdStatus result;
	274	result.m_wasSeenInJIT = false; // To my knowledge nobody that uses computeFor(VM&, Structure*, Identifier&) reads this field, but I might as well be honest: no, it wasn't seen in the JIT, since I computed it statically.
	275	unsigned attributes;
	276	JSCell* specificValue;
	277	result.m_offset = structure->get(vm, ident, attributes, specificValue);
	278	if (!isValidOffset(result.m_offset))
	279	return GetByIdStatus(TakesSlowPath); // It's probably a prototype lookup. Give up on life for now, even though we could totally be way smarter about it.
	280	if (attributes & Accessor)
	281	return GetByIdStatus(MakesCalls);
	282	if (structure->isDictionary())
	283	specificValue = 0;
	284	result.m_structureSet.add(structure);
	285	result.m_specificValue = JSValue(specificValue);
	286	return result;
	287	}
	288
6fe7ccc8 A	289	} // namespace JSC
6fe7ccc8 A	290