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https://github.com/darlinghq/darling-JavaScriptCore.git
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75 lines
3.5 KiB
C++
75 lines
3.5 KiB
C++
/*
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* Copyright (C) 2012, 2013 Apple Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "config.h"
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#include "ArrayAllocationProfile.h"
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#include "JSCellInlines.h"
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#include <algorithm>
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namespace JSC {
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void ArrayAllocationProfile::updateProfile()
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{
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// This is awkwardly racy but totally sound even when executed concurrently. The
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// worst cases go something like this:
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//
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// - Two threads race to execute this code; one of them succeeds in updating the
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// m_currentIndexingType and the other either updates it again, or sees a null
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// m_lastArray; if it updates it again then at worst it will cause the profile
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// to "forget" some array. That's still sound, since we don't promise that
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// this profile is a reflection of any kind of truth.
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//
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// - A concurrent thread reads m_lastArray, but that array is now dead. While
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// it's possible for that array to no longer be reachable, it cannot actually
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// be freed, since we require the GC to wait until all concurrent JITing
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// finishes.
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//
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// But one exception is vector length. We access vector length to get the vector
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// length hint. However vector length can be accessible only from the main
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// thread because large butterfly can be realloced in the main thread.
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// So for now, we update the allocation profile only from the main thread.
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ASSERT(!isCompilationThread());
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JSArray* lastArray = m_lastArray;
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if (!lastArray)
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return;
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if (LIKELY(Options::useArrayAllocationProfiling())) {
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// The basic model here is that we will upgrade ourselves to whatever the CoW version of lastArray is except ArrayStorage since we don't have CoW ArrayStorage.
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IndexingType indexingType = leastUpperBoundOfIndexingTypes(m_currentIndexingType & IndexingTypeMask, lastArray->indexingType());
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if (isCopyOnWrite(m_currentIndexingType)) {
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if (indexingType > ArrayWithContiguous)
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indexingType = ArrayWithContiguous;
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indexingType |= CopyOnWrite;
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}
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m_currentIndexingType = indexingType;
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m_largestSeenVectorLength = std::min(std::max(m_largestSeenVectorLength, lastArray->getVectorLength()), BASE_CONTIGUOUS_VECTOR_LEN_MAX);
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}
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m_lastArray = nullptr;
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}
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} // namespace JSC
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