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/*
* Copyright (C) 2016-2017 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 "WeakSet.h"
namespace JSC {
class SlotVisitor;
// WebKit has a good malloc that already knows what to do for large allocations. The GC shouldn't
// have to think about such things. That's where LargeAllocation comes in. We will allocate large
// objects directly using malloc, and put the LargeAllocation header just before them. We can detect
// when a HeapCell* is a LargeAllocation because it will have the MarkedBlock::atomSize / 2 bit set.
class LargeAllocation : public BasicRawSentinelNode<LargeAllocation> {
public:
static LargeAllocation* tryCreate(Heap&, size_t, Subspace*);
~LargeAllocation();
static LargeAllocation* fromCell(const void* cell)
{
return bitwise_cast<LargeAllocation*>(bitwise_cast<char*>(cell) - headerSize());
}
HeapCell* cell() const
{
return bitwise_cast<HeapCell*>(bitwise_cast<char*>(this) + headerSize());
}
static bool isLargeAllocation(HeapCell* cell)
{
return bitwise_cast<uintptr_t>(cell) & halfAlignment;
}
void lastChanceToFinalize();
Heap* heap() const { return m_weakSet.heap(); }
VM* vm() const { return m_weakSet.vm(); }
WeakSet& weakSet() { return m_weakSet; }
void shrink();
void visitWeakSet(SlotVisitor&);
void reapWeakSet();
void clearNewlyAllocated() { m_isNewlyAllocated = false; }
void flip();
bool isNewlyAllocated() const { return m_isNewlyAllocated; }
ALWAYS_INLINE bool isMarked() { return m_isMarked.load(std::memory_order_relaxed); }
ALWAYS_INLINE bool isMarked(HeapCell*) { return isMarked(); }
ALWAYS_INLINE bool isMarked(HeapCell*, Dependency) { return isMarked(); }
ALWAYS_INLINE bool isMarkedConcurrently(HeapVersion, HeapCell*) { return isMarked(); }
bool isLive() { return isMarked() || isNewlyAllocated(); }
bool hasValidCell() const { return m_hasValidCell; }
bool isEmpty();
size_t cellSize() const { return m_cellSize; }
bool aboveLowerBound(const void* rawPtr)
{
char* ptr = bitwise_cast<char*>(rawPtr);
char* begin = bitwise_cast<char*>(cell());
return ptr >= begin;
}
bool belowUpperBound(const void* rawPtr)
{
char* ptr = bitwise_cast<char*>(rawPtr);
char* begin = bitwise_cast<char*>(cell());
char* end = begin + cellSize();
// We cannot #include IndexingHeader.h because reasons. The fact that IndexingHeader is 8
// bytes is wired deep into our engine, so this isn't so bad.
size_t sizeOfIndexingHeader = 8;
return ptr <= end + sizeOfIndexingHeader;
}
bool contains(const void* rawPtr)
{
return aboveLowerBound(rawPtr) && belowUpperBound(rawPtr);
}
const AllocatorAttributes& attributes() const { return m_attributes; }
Dependency aboutToMark(HeapVersion) { return nullDependency(); }
ALWAYS_INLINE bool testAndSetMarked()
{
// This method is usually called when the object is already marked. This avoids us
// having to CAS in that case. It's profitable to reduce the total amount of CAS
// traffic.
if (isMarked())
return true;
return m_isMarked.compareExchangeStrong(false, true);
}
ALWAYS_INLINE bool testAndSetMarked(HeapCell*, Dependency) { return testAndSetMarked(); }
void clearMarked() { m_isMarked.store(false); }
void noteMarked() { }
#if ASSERT_DISABLED
void assertValidCell(VM&, HeapCell*) const { }
#else
void assertValidCell(VM&, HeapCell*) const;
#endif
void sweep();
void destroy();
void dump(PrintStream&) const;
private:
LargeAllocation(Heap&, size_t, Subspace*);
static const unsigned alignment = MarkedBlock::atomSize;
static const unsigned halfAlignment = alignment / 2;
static unsigned headerSize();
size_t m_cellSize;
bool m_isNewlyAllocated;
bool m_hasValidCell;
Atomic<bool> m_isMarked;
AllocatorAttributes m_attributes;
Subspace* m_subspace;
WeakSet m_weakSet;
};
inline unsigned LargeAllocation::headerSize()
{
return ((sizeof(LargeAllocation) + halfAlignment - 1) & ~(halfAlignment - 1)) | halfAlignment;
}
} // namespace JSC
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