/* * Copyright (C) 2012, 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. */ #include "config.h" #include "ArrayAllocationProfile.h" #include "JSCellInlines.h" #include <algorithm> namespace JSC { void ArrayAllocationProfile::updateProfile() { // This is awkwardly racy but totally sound even when executed concurrently. The // worst cases go something like this: // // - Two threads race to execute this code; one of them succeeds in updating the // m_currentIndexingType and the other either updates it again, or sees a null // m_lastArray; if it updates it again then at worst it will cause the profile // to "forget" some array. That's still sound, since we don't promise that // this profile is a reflection of any kind of truth. // // - A concurrent thread reads m_lastArray, but that array is now dead. While // it's possible for that array to no longer be reachable, it cannot actually // be freed, since we require the GC to wait until all concurrent JITing // finishes. // // But one exception is vector length. We access vector length to get the vector // length hint. However vector length can be accessible only from the main // thread because large butterfly can be realloced in the main thread. // So for now, we update the allocation profile only from the main thread. ASSERT(!isCompilationThread()); JSArray* lastArray = m_lastArray; if (!lastArray) return; if (LIKELY(Options::useArrayAllocationProfiling())) { // 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. IndexingType indexingType = leastUpperBoundOfIndexingTypes(m_currentIndexingType & IndexingTypeMask, lastArray->indexingType()); if (isCopyOnWrite(m_currentIndexingType)) { if (indexingType > ArrayWithContiguous) indexingType = ArrayWithContiguous; indexingType |= CopyOnWrite; } m_currentIndexingType = indexingType; m_largestSeenVectorLength = std::min(std::max(m_largestSeenVectorLength, lastArray->getVectorLength()), BASE_CONTIGUOUS_VECTOR_LEN_MAX); } m_lastArray = nullptr; } } // namespace JSC