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/*
* Copyright (C) 2013 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.
*/
#pragma once
#include "StaticPropertyAnalysis.h"
#include <wtf/HashMap.h>
namespace JSC {
// Used for flow-insensitive static analysis of the number of properties assigned to an object.
// We use this analysis with other runtime data to produce an optimization guess. This analysis
// is understood to be lossy, and it's OK if it turns out to be wrong sometimes.
class StaticPropertyAnalyzer {
public:
void createThis(RegisterID* dst, JSInstructionStream::MutableRef instructionRef);
void newObject(RegisterID* dst, JSInstructionStream::MutableRef instructionRef);
void putById(RegisterID* dst, unsigned propertyIndex); // propertyIndex is an index into a uniqued set of strings.
void mov(RegisterID* dst, RegisterID* src);
void kill();
void kill(RegisterID* dst);
private:
void kill(StaticPropertyAnalysis*);
typedef UncheckedKeyHashMap<int, RefPtr<StaticPropertyAnalysis>, WTF::IntHash<int>, WTF::UnsignedWithZeroKeyHashTraits<int>> AnalysisMap;
AnalysisMap m_analyses;
};
inline void StaticPropertyAnalyzer::createThis(RegisterID* dst, JSInstructionStream::MutableRef instructionRef)
{
AnalysisMap::AddResult addResult = m_analyses.add(
dst->index(), StaticPropertyAnalysis::create(WTFMove(instructionRef)));
ASSERT_UNUSED(addResult, addResult.isNewEntry); // Can't have two 'this' in the same constructor.
}
inline void StaticPropertyAnalyzer::newObject(RegisterID* dst, JSInstructionStream::MutableRef instructionRef)
{
auto analysis = StaticPropertyAnalysis::create(WTFMove(instructionRef));
AnalysisMap::AddResult addResult = m_analyses.add(dst->index(), analysis.copyRef());
if (!addResult.isNewEntry) {
kill(addResult.iterator->value.get());
addResult.iterator->value = WTFMove(analysis);
}
}
inline void StaticPropertyAnalyzer::putById(RegisterID* dst, unsigned propertyIndex)
{
StaticPropertyAnalysis* analysis = m_analyses.get(dst->index());
if (!analysis)
return;
analysis->addPropertyIndex(propertyIndex);
}
inline void StaticPropertyAnalyzer::mov(RegisterID* dst, RegisterID* src)
{
RefPtr<StaticPropertyAnalysis> analysis = m_analyses.get(src->index());
if (!analysis) {
kill(dst);
return;
}
AnalysisMap::AddResult addResult = m_analyses.add(dst->index(), analysis);
if (!addResult.isNewEntry) {
kill(addResult.iterator->value.get());
addResult.iterator->value = WTFMove(analysis);
}
}
inline void StaticPropertyAnalyzer::kill(StaticPropertyAnalysis* analysis)
{
if (!analysis)
return;
if (!analysis->hasOneRef()) // Aliases for this object still exist, so it might acquire more properties.
return;
analysis->record();
}
inline void StaticPropertyAnalyzer::kill(RegisterID* dst)
{
// We observe kills in order to avoid piling on properties to an object after
// its bytecode register has been recycled.
// Consider these cases:
// (1) Aliased temporary
// var o1 = { name: name };
// var o2 = { name: name };
// (2) Aliased local -- no control flow
// var local;
// local = new Object;
// local.name = name;
// ...
// local = lookup();
// local.didLookup = true;
// ...
// (3) Aliased local -- control flow
// var local;
// if (condition)
// local = { };
// else {
// local = new Object;
// }
// local.name = name;
// (Note: our default codegen for "new Object" looks like case (3).)
// Case (1) is easy because temporaries almost never survive across control flow.
// Cases (2) and (3) are hard. Case (2) should kill "local", while case (3) should
// not. There is no great way to solve these cases with simple static analysis.
// Since this is a simple static analysis, we just try to catch the simplest cases,
// so we accept kills to any registers except for registers that have no inferred
// properties yet.
AnalysisMap::iterator it = m_analyses.find(dst->index());
if (it == m_analyses.end())
return;
if (!it->value->propertyIndexCount())
return;
kill(it->value.get());
m_analyses.remove(it);
}
inline void StaticPropertyAnalyzer::kill()
{
while (m_analyses.size())
kill(m_analyses.take(m_analyses.begin()->key).get());
}
} // namespace JSC
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