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/*
* Copyright (C) 2017 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 "MarkedBlock.h"
#include "MarkedSpace.h"
#include <wtf/text/CString.h>
namespace JSC {
class AlignedMemoryAllocator;
// The idea of subspaces is that you can provide some custom behavior for your objects if you
// allocate them from a custom Subspace in which you override some of the virtual methods. This
// class is the baseclass of Subspaces and it provides a reasonable default implementation, where
// sweeping assumes immortal structure. The common ways of overriding this are:
//
// - Provide customized destructor behavior. You can change how the destructor is called. You can
// also specialize the destructor call in the loop.
//
// - Use the Subspace as a quick way to iterate all of the objects in that subspace.
class Subspace {
WTF_MAKE_NONCOPYABLE(Subspace);
WTF_MAKE_FAST_ALLOCATED;
public:
JS_EXPORT_PRIVATE Subspace(CString name, Heap&, AllocatorAttributes, AlignedMemoryAllocator*);
JS_EXPORT_PRIVATE virtual ~Subspace();
const char* name() const { return m_name.data(); }
MarkedSpace& space() const { return m_space; }
const AllocatorAttributes& attributes() const { return m_attributes; }
AlignedMemoryAllocator* alignedMemoryAllocator() const { return m_alignedMemoryAllocator; }
// The purpose of overriding this is to specialize the sweep for your destructors. This won't
// be called for no-destructor blocks. This must call MarkedBlock::finishSweepKnowingSubspace.
virtual void finishSweep(MarkedBlock::Handle&, FreeList*);
// These get called for large objects.
virtual void destroy(VM&, JSCell*);
MarkedAllocator* tryAllocatorFor(size_t);
MarkedAllocator* allocatorFor(size_t);
JS_EXPORT_PRIVATE void* allocate(size_t);
JS_EXPORT_PRIVATE void* allocate(GCDeferralContext*, size_t);
JS_EXPORT_PRIVATE void* tryAllocate(size_t);
JS_EXPORT_PRIVATE void* tryAllocate(GCDeferralContext*, size_t);
void prepareForAllocation();
void didCreateFirstAllocator(MarkedAllocator* allocator) { m_allocatorForEmptyAllocation = allocator; }
// Finds an empty block from any Subspace that agrees to trade blocks with us.
MarkedBlock::Handle* findEmptyBlockToSteal();
template<typename Func>
void forEachAllocator(const Func&);
template<typename Func>
void forEachMarkedBlock(const Func&);
template<typename Func>
void forEachNotEmptyMarkedBlock(const Func&);
template<typename Func>
void forEachLargeAllocation(const Func&);
template<typename Func>
void forEachMarkedCell(const Func&);
template<typename Func>
void forEachLiveCell(const Func&);
static ptrdiff_t offsetOfAllocatorForSizeStep() { return OBJECT_OFFSETOF(Subspace, m_allocatorForSizeStep); }
MarkedAllocator** allocatorForSizeStep() { return &m_allocatorForSizeStep[0]; }
private:
MarkedAllocator* allocatorForSlow(size_t);
// These slow paths are concerned with large allocations and allocator creation.
void* allocateSlow(GCDeferralContext*, size_t);
void* tryAllocateSlow(GCDeferralContext*, size_t);
void didAllocate(void*);
MarkedSpace& m_space;
CString m_name;
AllocatorAttributes m_attributes;
AlignedMemoryAllocator* m_alignedMemoryAllocator;
std::array<MarkedAllocator*, MarkedSpace::numSizeClasses> m_allocatorForSizeStep;
MarkedAllocator* m_firstAllocator { nullptr };
MarkedAllocator* m_allocatorForEmptyAllocation { nullptr }; // Uses the MarkedSpace linked list of blocks.
SentinelLinkedList<LargeAllocation, BasicRawSentinelNode<LargeAllocation>> m_largeAllocations;
};
ALWAYS_INLINE MarkedAllocator* Subspace::tryAllocatorFor(size_t size)
{
if (size <= MarkedSpace::largeCutoff)
return m_allocatorForSizeStep[MarkedSpace::sizeClassToIndex(size)];
return nullptr;
}
ALWAYS_INLINE MarkedAllocator* Subspace::allocatorFor(size_t size)
{
if (size <= MarkedSpace::largeCutoff) {
if (MarkedAllocator* result = m_allocatorForSizeStep[MarkedSpace::sizeClassToIndex(size)])
return result;
return allocatorForSlow(size);
}
return nullptr;
}
} // namespace JSC
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