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ConservativeRoots.cpp
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ConservativeRoots.cpp
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/*
* Copyright (C) 2011 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. AND ITS CONTRIBUTORS ``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 ITS 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 "ConservativeRoots.h"
namespace JSC {
inline bool isPointerAligned(void* p)
{
return !((intptr_t)(p) & (sizeof(char*) - 1));
}
void ConservativeRoots::grow()
{
size_t newCapacity = m_capacity == inlineCapacity ? nonInlineCapacity : m_capacity * 2;
JSCell** newRoots = static_cast<JSCell**>(OSAllocator::reserveAndCommit(newCapacity * sizeof(JSCell*)));
memcpy(newRoots, m_roots, m_size * sizeof(JSCell*));
if (m_roots != m_inlineRoots)
OSAllocator::decommitAndRelease(m_roots, m_capacity * sizeof(JSCell*));
m_capacity = newCapacity;
m_roots = newRoots;
}
inline void ConservativeRoots::add(void* p, TinyBloomFilter filter)
{
MarkedBlock* candidate = MarkedBlock::blockFor(p);
if (filter.ruleOut(reinterpret_cast<Bits>(candidate))) {
ASSERT(!candidate || !m_blocks->set().contains(candidate));
return;
}
if (!MarkedBlock::isAtomAligned(p))
return;
if (!m_blocks->set().contains(candidate))
return;
// The conservative set inverts the typical meaning of mark bits: We only
// visit marked pointers, and our visit clears the mark bit. This efficiently
// sifts out pointers to dead objects and duplicate pointers.
if (!candidate->testAndClearMarked(p))
return;
if (m_size == m_capacity)
grow();
m_roots[m_size++] = static_cast<JSCell*>(p);
}
void ConservativeRoots::add(void* begin, void* end)
{
ASSERT(begin <= end);
ASSERT((static_cast<char*>(end) - static_cast<char*>(begin)) < 0x1000000);
ASSERT(isPointerAligned(begin));
ASSERT(isPointerAligned(end));
TinyBloomFilter filter = m_blocks->filter(); // Make a local copy of filter to show the compiler it won't alias, and can be register-allocated.
for (char** it = static_cast<char**>(begin); it != static_cast<char**>(end); ++it)
add(*it, filter);
}
} // namespace JSC