Source/JavaScriptCore/jit/PolymorphicCallStubRoutine.cpp

/*
 * Copyright (C) 2015-2018 Apple Inc. All rights reserved.
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#include "config.h"
#include "PolymorphicCallStubRoutine.h"

#if ENABLE(JIT)

#include "CallLinkInfo.h"
#include "CodeBlock.h"
#include "FullCodeOrigin.h"
#include "JSCInlines.h"
#include "LinkBuffer.h"

namespace JSC {

PolymorphicCallNode::~PolymorphicCallNode()
{
    if (isOnList())
        remove();
}

void PolymorphicCallNode::unlink(VM& vm)
{
    if (m_callLinkInfo) {
        if (Options::dumpDisassembly())
            dataLog("Unlinking polymorphic call at ", m_callLinkInfo->callReturnLocation(), ", ", m_callLinkInfo->codeOrigin(), "\n");

        m_callLinkInfo->unlink(vm);
    }

    if (isOnList())
        remove();
}

void PolymorphicCallNode::clearCallLinkInfo()
{
    m_callLinkInfo = nullptr;
}

void PolymorphicCallCase::dump(PrintStream& out) const
{
    out.print("<variant = ", m_variant, ", codeBlock = ", pointerDump(m_codeBlock), ">");
}

PolymorphicCallStubRoutine::PolymorphicCallStubRoutine(
    const MacroAssemblerCodeRef<JITStubRoutinePtrTag>& codeRef, VM& vm, const JSCell* owner, ExecState* callerFrame,
    CallLinkInfo& info, const Vector<PolymorphicCallCase>& cases,
    UniqueArray<uint32_t>&& fastCounts)
    : GCAwareJITStubRoutine(codeRef, vm)
    , m_fastCounts(WTFMove(fastCounts))
{
    for (PolymorphicCallCase callCase : cases) {
        m_variants.append(WriteBarrier<JSCell>(vm, owner, callCase.variant().rawCalleeCell()));
        if (shouldDumpDisassemblyFor(callerFrame->codeBlock()))
            dataLog("Linking polymorphic call in ", FullCodeOrigin(callerFrame->codeBlock(), callerFrame->codeOrigin()), " to ", callCase.variant(), ", codeBlock = ", pointerDump(callCase.codeBlock()), "\n");
        if (CodeBlock* codeBlock = callCase.codeBlock())
            codeBlock->linkIncomingPolymorphicCall(callerFrame, m_callNodes.add(&info));
    }
    m_variants.shrinkToFit();
    WTF::storeStoreFence();
}

PolymorphicCallStubRoutine::~PolymorphicCallStubRoutine() { }

CallVariantList PolymorphicCallStubRoutine::variants() const
{
    CallVariantList result;
    for (size_t i = 0; i < m_variants.size(); ++i)
        result.append(CallVariant(m_variants[i].get()));
    return result;
}

bool PolymorphicCallStubRoutine::hasEdges() const
{
    // The FTL does not count edges in its poly call stub routines. If the FTL went poly call, then
    // it's not meaningful to keep profiling - we can just leave it at that. Remember, the FTL would
    // have had full edge profiling from the DFG, and based on this information, it would have
    // decided to go poly.
    //
    // There probably are very-difficult-to-imagine corner cases where the FTL not doing edge
    // profiling is bad for polyvariant inlining. But polyvariant inlining is profitable sometimes
    // while not having to increment counts is profitable always. So, we let the FTL run faster and
    // not keep counts.
    return !!m_fastCounts;
}

CallEdgeList PolymorphicCallStubRoutine::edges() const
{
    RELEASE_ASSERT(m_fastCounts);
    
    CallEdgeList result;
    for (size_t i = 0; i < m_variants.size(); ++i)
        result.append(CallEdge(CallVariant(m_variants[i].get()), m_fastCounts[i]));
    return result;
}

void PolymorphicCallStubRoutine::clearCallNodesFor(CallLinkInfo* info)
{
    for (Bag<PolymorphicCallNode>::iterator iter = m_callNodes.begin(); !!iter; ++iter) {
        PolymorphicCallNode& node = **iter;
        // All nodes should point to info, but okay to be a little paranoid.
        if (node.hasCallLinkInfo(info))
            node.clearCallLinkInfo();
    }
}

bool PolymorphicCallStubRoutine::visitWeak(VM& vm)
{
    bool isStillLive = true;
    forEachDependentCell([&](JSCell* cell) {
        isStillLive &= vm.heap.isMarked(cell);
    });
    return isStillLive;
}

void PolymorphicCallStubRoutine::markRequiredObjectsInternal(SlotVisitor& visitor)
{
    for (auto& variant : m_variants)
        visitor.append(variant);
}

} // namespace JSC

#endif // ENABLE(JIT)