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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.
*/
#ifndef ObjectAllocationProfile_h
#define ObjectAllocationProfile_h
#include "VM.h"
#include "JSGlobalObject.h"
#include "ObjectPrototype.h"
#include "SlotVisitor.h"
#include "WriteBarrier.h"
namespace JSC {
class ObjectAllocationProfile {
friend class LLIntOffsetsExtractor;
public:
static ptrdiff_t offsetOfAllocator() { return OBJECT_OFFSETOF(ObjectAllocationProfile, m_allocator); }
static ptrdiff_t offsetOfStructure() { return OBJECT_OFFSETOF(ObjectAllocationProfile, m_structure); }
ObjectAllocationProfile()
: m_allocator(0)
{
}
bool isNull() { return !m_allocator; }
void initialize(VM& vm, JSCell* owner, JSObject* prototype, unsigned inferredInlineCapacity)
{
ASSERT(!m_allocator);
ASSERT(!m_structure);
unsigned inlineCapacity = 0;
if (inferredInlineCapacity < JSFinalObject::defaultInlineCapacity()) {
// Try to shrink the object based on static analysis.
inferredInlineCapacity += possibleDefaultPropertyCount(vm, prototype);
if (!inferredInlineCapacity) {
// Empty objects are rare, so most likely the static analyzer just didn't
// see the real initializer function. This can happen with helper functions.
inferredInlineCapacity = JSFinalObject::defaultInlineCapacity();
} else if (inferredInlineCapacity > JSFinalObject::defaultInlineCapacity()) {
// Default properties are weak guesses, so don't allow them to turn a small
// object into a large object.
inferredInlineCapacity = JSFinalObject::defaultInlineCapacity();
}
inlineCapacity = inferredInlineCapacity;
ASSERT(inlineCapacity < JSFinalObject::maxInlineCapacity());
} else {
// Normal or large object.
inlineCapacity = inferredInlineCapacity;
if (inlineCapacity > JSFinalObject::maxInlineCapacity())
inlineCapacity = JSFinalObject::maxInlineCapacity();
}
ASSERT(inlineCapacity > 0);
ASSERT(inlineCapacity <= JSFinalObject::maxInlineCapacity());
size_t allocationSize = JSFinalObject::allocationSize(inlineCapacity);
MarkedAllocator* allocator = &vm.heap.allocatorForObjectWithoutDestructor(allocationSize);
ASSERT(allocator->cellSize());
// Take advantage of extra inline capacity available in the size class.
size_t slop = (allocator->cellSize() - allocationSize) / sizeof(WriteBarrier<Unknown>);
inlineCapacity += slop;
if (inlineCapacity > JSFinalObject::maxInlineCapacity())
inlineCapacity = JSFinalObject::maxInlineCapacity();
Structure* structure = vm.prototypeMap.emptyObjectStructureForPrototype(prototype, inlineCapacity);
// Ensure that if another thread sees the structure, it will see it properly created
WTF::storeStoreFence();
m_allocator = allocator;
m_structure.set(vm, owner, structure);
}
Structure* structure()
{
Structure* structure = m_structure.get();
// Ensure that if we see the structure, it has been properly created
WTF::loadLoadFence();
return structure;
}
unsigned inlineCapacity() { return structure()->inlineCapacity(); }
void clear()
{
m_allocator = 0;
m_structure.clear();
ASSERT(isNull());
}
void visitAggregate(SlotVisitor& visitor)
{
visitor.append(&m_structure);
}
private:
unsigned possibleDefaultPropertyCount(VM& vm, JSObject* prototype)
{
if (prototype == prototype->globalObject()->objectPrototype())
return 0;
size_t count = 0;
PropertyNameArray propertyNameArray(&vm, PropertyNameMode::StringsAndSymbols);
prototype->structure()->getPropertyNamesFromStructure(vm, propertyNameArray, EnumerationMode());
PropertyNameArrayData::PropertyNameVector& propertyNameVector = propertyNameArray.data()->propertyNameVector();
for (size_t i = 0; i < propertyNameVector.size(); ++i) {
JSValue value = prototype->getDirect(vm, propertyNameVector[i]);
// Functions are common, and are usually class-level objects that are not overridden.
if (jsDynamicCast<JSFunction*>(value))
continue;
++count;
}
return count;
}
MarkedAllocator* m_allocator; // Precomputed to make things easier for generated code.
WriteBarrier<Structure> m_structure;
};
} // namespace JSC
#endif // ObjectAllocationProfile_h
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