Source/JavaScriptCore/jit/GCAwareJITStubRoutine.h

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#pragma once

#if ENABLE(JIT)

#include "JITStubRoutine.h"
#include "JSObject.h"
#include "WriteBarrier.h"
#include <wtf/FixedVector.h>
#include <wtf/Hasher.h>
#include <wtf/Vector.h>

namespace JSC {
namespace DFG {
class CodeOriginPool;
}

class AccessCase;
class CallLinkInfo;
class JITStubRoutineSet;

// Use this stub routine if you know that your code might be on stack when
// either GC or other kinds of stub deletion happen. Basicaly, if your stub
// routine makes calls (either to JS code or to C++ code) then you should
// assume that it's possible for that JS or C++ code to do something that
// causes the system to try to delete your routine. Using this routine type
// ensures that the actual deletion is delayed until the GC proves that the
// routine is no longer running. You can also subclass this routine if you
// want to mark additional objects during GC in those cases where the
// routine is known to be executing, or if you want to force this routine to
// keep other routines alive (for example due to the use of a slow-path
// list which does not get reclaimed all at once).
class GCAwareJITStubRoutine : public JITStubRoutine {
public:
    GCAwareJITStubRoutine(const MacroAssemblerCodeRef<JITStubRoutinePtrTag>&);
    ~GCAwareJITStubRoutine() override;

    static Ref<JITStubRoutine> create(VM& vm, const MacroAssemblerCodeRef<JITStubRoutinePtrTag>& code)
    {
        auto stub = adoptRef(*new GCAwareJITStubRoutine(code));
        stub->makeGCAware(vm);
        return stub;
    }

    template<typename Visitor>
    void markRequiredObjects(Visitor& visitor)
    {
        markRequiredObjectsInternal(visitor);
    }
    
    void deleteFromGC();

    void makeGCAware(VM&);
    
protected:
    void observeZeroRefCount() override;
    
    virtual void markRequiredObjectsInternal(AbstractSlotVisitor&) { }
    virtual void markRequiredObjectsInternal(SlotVisitor&) { }

private:
    friend class JITStubRoutineSet;

    bool m_mayBeExecuting { false };
    bool m_isJettisoned { false };
    bool m_isGCAware { false };
};

class PolymorphicAccessJITStubRoutine : public GCAwareJITStubRoutine {
public:
    using Base = GCAwareJITStubRoutine;

    PolymorphicAccessJITStubRoutine(const MacroAssemblerCodeRef<JITStubRoutinePtrTag>&, VM&, FixedVector<RefPtr<AccessCase>>&&, FixedVector<StructureID>&&);

    const FixedVector<RefPtr<AccessCase>>& cases() const { return m_cases; }
    const FixedVector<StructureID>& weakStructures() const { return m_weakStructures; }

    unsigned hash() const
    {
        if (!m_hash)
            m_hash = computeHash(m_cases, m_weakStructures);
        return m_hash;
    }

    static unsigned computeHash(const FixedVector<RefPtr<AccessCase>>&, const FixedVector<StructureID>&);

protected:
    void observeZeroRefCount() override;

private:
    VM& m_vm;
    FixedVector<RefPtr<AccessCase>> m_cases;
    FixedVector<StructureID> m_weakStructures;
};

// Use this if you want to mark one additional object during GC if your stub
// routine is known to be executing.
class MarkingGCAwareJITStubRoutine : public PolymorphicAccessJITStubRoutine {
public:
    using Base = PolymorphicAccessJITStubRoutine;

    MarkingGCAwareJITStubRoutine(
        const MacroAssemblerCodeRef<JITStubRoutinePtrTag>&, VM&, FixedVector<RefPtr<AccessCase>>&&, FixedVector<StructureID>&&, const JSCell* owner, const Vector<JSCell*>&, Bag<CallLinkInfo>&&);
    ~MarkingGCAwareJITStubRoutine() override;
    
protected:
    template<typename Visitor> void markRequiredObjectsInternalImpl(Visitor&);
    void markRequiredObjectsInternal(AbstractSlotVisitor&) final;
    void markRequiredObjectsInternal(SlotVisitor&) final;

private:
    FixedVector<WriteBarrier<JSCell>> m_cells;
    Bag<CallLinkInfo> m_callLinkInfos;
};


// The stub has exception handlers in it. So it clears itself from exception
// handling table when it dies. It also frees space in CodeOrigin table
// for new exception handlers to use the same DisposableCallSiteIndex.
class GCAwareJITStubRoutineWithExceptionHandler final : public MarkingGCAwareJITStubRoutine {
public:
    using Base = MarkingGCAwareJITStubRoutine;

    GCAwareJITStubRoutineWithExceptionHandler(const MacroAssemblerCodeRef<JITStubRoutinePtrTag>&, VM&, FixedVector<RefPtr<AccessCase>>&&, FixedVector<StructureID>&&, const JSCell* owner, const Vector<JSCell*>&, Bag<CallLinkInfo>&&, CodeBlock*, DisposableCallSiteIndex);
    ~GCAwareJITStubRoutineWithExceptionHandler() final;

    void aboutToDie() final;
    void observeZeroRefCount() final;

private:
    CodeBlock* m_codeBlockWithExceptionHandler;
#if ENABLE(DFG_JIT)
    RefPtr<DFG::CodeOriginPool> m_codeOriginPool;
#endif
    DisposableCallSiteIndex m_exceptionHandlerCallSiteIndex;
};

// Helper for easily creating a GC-aware JIT stub routine. For the varargs,
// pass zero or more JSCell*'s. This will either create a JITStubRoutine, a
// GCAwareJITStubRoutine, or an ObjectMarkingGCAwareJITStubRoutine as
// appropriate. Generally you only need to pass pointers that will be used
// after the first call to C++ or JS.
// 
// Ref<PolymorphicAccessJITStubRoutine> createICJITStubRoutine(
//    const MacroAssemblerCodeRef<JITStubRoutinePtrTag>& code,
//    VM& vm,
//    FixedVector<RefPtr<AccessCase>>&& cases,
//    const JSCell* owner,
//    bool makesCalls,
//    ...);
//
// Note that we don't actually use C-style varargs because that leads to
// strange type-related problems. For example it would preclude us from using
// our custom of passing '0' as NULL pointer. Besides, when I did try to write
// this function using varargs, I ended up with more code than this simple
// way.

Ref<PolymorphicAccessJITStubRoutine> createICJITStubRoutine(
    const MacroAssemblerCodeRef<JITStubRoutinePtrTag>&, FixedVector<RefPtr<AccessCase>>&& cases, FixedVector<StructureID>&& weakStructures, VM&, const JSCell* owner, bool makesCalls,
    const Vector<JSCell*>&, Bag<CallLinkInfo>&& callLinkInfos,
    CodeBlock* codeBlockForExceptionHandlers, DisposableCallSiteIndex exceptionHandlingCallSiteIndex);

} // namespace JSC

#endif // ENABLE(JIT)