Source/JavaScriptCore/dfg/DFGDesiredWeakReferences.cpp

/*
 * Copyright (C) 2013-2016 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
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 *    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
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#include "config.h"
#include "DFGDesiredWeakReferences.h"

#if ENABLE(DFG_JIT)

#include "CodeBlock.h"
#include "DFGCommonData.h"
#include "JSCInlines.h"

namespace JSC { namespace DFG {

DesiredWeakReferences::DesiredWeakReferences()
    : m_codeBlock(nullptr)
{
}

DesiredWeakReferences::DesiredWeakReferences(CodeBlock* codeBlock)
    : m_codeBlock(codeBlock)
{
}

DesiredWeakReferences::~DesiredWeakReferences()
{
}

void DesiredWeakReferences::addLazily(JSCell* cell)
{
    if (cell)
        m_references.add(cell);
}

void DesiredWeakReferences::addLazily(JSValue value)
{
    if (value.isCell())
        addLazily(value.asCell());
}

bool DesiredWeakReferences::contains(JSCell* cell)
{
    return m_references.contains(cell);
}

void DesiredWeakReferences::reallyAdd(VM& vm, CommonData* common)
{
    ASSERT(vm.heap.isDeferred());
    for (JSCell* target : m_references) {
        if (Structure* structure = jsDynamicCast<Structure*>(vm, target)) {
            ConcurrentJSLocker locker(m_codeBlock->m_lock);
            // We do not emit WriteBarrier here since (1) GC is deferred and (2) we emit write-barrier on CodeBlock when finishing DFG::Plan::reallyAdd.
            common->weakStructureReferences.append(structure->id());
        } else {
            // There are weird relationships in how optimized CodeBlocks
            // point to other CodeBlocks. We don't want to have them be
            // part of the weak pointer set. For example, an optimized CodeBlock
            // having a weak pointer to itself will cause it to get collected.
            RELEASE_ASSERT(!jsDynamicCast<CodeBlock*>(vm, target));

            ConcurrentJSLocker locker(m_codeBlock->m_lock);
            common->weakReferences.append(
                WriteBarrier<JSCell>(vm, m_codeBlock, target));
        }
    }
}

void DesiredWeakReferences::visitChildren(SlotVisitor& visitor)
{
    for (JSCell* target : m_references)
        visitor.appendUnbarriered(target);
}

} } // namespace JSC::DFG

#endif // ENABLE(DFG_JIT)