Source/JavaScriptCore/dfg/DFGDesiredWeakReferences.cpp

/*
 * Copyright (C) 2013-2021 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 "DFGDesiredWeakReferences.h"

#if ENABLE(DFG_JIT)

#include "CodeBlock.h"
#include "DFGCommonData.h"
#include "JSCJSValueInlines.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)
{
    // We do not emit WriteBarrier here since (1) GC is deferred and (2) we emit write-barrier on CodeBlock when finishing DFG::Plan::reallyAdd.
    ASSERT(vm.heap.isDeferred());

    Vector<StructureID> weakStructureReferences;
    Vector<WriteBarrier<JSCell>> weakReferences;
    for (JSCell* target : m_references) {
        if (Structure* structure = jsDynamicCast<Structure*>(vm, target))
            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));
            weakReferences.append(WriteBarrier<JSCell>(vm, m_codeBlock, target));
        }
    }
    if (!weakStructureReferences.isEmpty() || !weakReferences.isEmpty()) {
        ConcurrentJSLocker locker(m_codeBlock->m_lock);
        ASSERT(common->m_weakStructureReferences.isEmpty());
        ASSERT(common->m_weakReferences.isEmpty());
        common->m_weakStructureReferences = WTFMove(weakStructureReferences);
        common->m_weakReferences = WTFMove(weakReferences);
    }
}

template<typename Visitor>
void DesiredWeakReferences::visitChildren(Visitor& visitor)
{
    for (JSCell* target : m_references)
        visitor.appendUnbarriered(target);
}

template void DesiredWeakReferences::visitChildren(AbstractSlotVisitor&);
template void DesiredWeakReferences::visitChildren(SlotVisitor&);

} } // namespace JSC::DFG

#endif // ENABLE(DFG_JIT)