Source/JavaScriptCore/bytecode/InternalFunctionAllocationProfile.h

/*
 * Copyright (C) 2016-2017 Apple Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
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#pragma once

#include "JSGlobalObject.h"
#include "SlotVisitor.h"
#include "WriteBarrier.h"

namespace JSC {

class InternalFunctionAllocationProfile {
public:
    static inline ptrdiff_t offsetOfStructure() { return OBJECT_OFFSETOF(InternalFunctionAllocationProfile, m_structure); }

    Structure* structure() { return m_structure.get(); }
    Structure* createAllocationStructureFromBase(VM&, JSGlobalObject*, JSCell* owner, JSObject* prototype, Structure* base);

    void clear() { m_structure.clear(); }
    void visitAggregate(SlotVisitor& visitor) { visitor.append(m_structure); }

private:
    WriteBarrier<Structure> m_structure;
};

inline Structure* InternalFunctionAllocationProfile::createAllocationStructureFromBase(VM& vm, JSGlobalObject* baseGlobalObject, JSCell* owner, JSObject* prototype, Structure* baseStructure)
{
    ASSERT(!m_structure || m_structure.get()->classInfo() != baseStructure->classInfo());
    ASSERT(baseStructure->hasMonoProto());

    Structure* structure;
    // FIXME: Implement polymorphic prototypes for subclasses of builtin types:
    // https://bugs.webkit.org/show_bug.cgi?id=177318
    if (prototype == baseStructure->storedPrototype())
        structure = baseStructure;
    else
        structure = vm.structureCache.emptyStructureForPrototypeFromBaseStructure(baseGlobalObject, prototype, baseStructure);

    // Ensure that if another thread sees the structure, it will see it properly created.
    WTF::storeStoreFence();

    m_structure.set(vm, owner, structure);
    return m_structure.get();
}

} // namespace JSC