Source/JavaScriptCore/jit/GCAwareJITStubRoutine.cpp

/*
 * Copyright (C) 2012-2018 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
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 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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#include "config.h"
#include "GCAwareJITStubRoutine.h"

#if ENABLE(JIT)

#include "CodeBlock.h"
#include "DFGCommonData.h"
#include "Heap.h"
#include "VM.h"
#include "JITStubRoutineSet.h"
#include "JSCellInlines.h"
#include <wtf/RefPtr.h>

namespace JSC {

GCAwareJITStubRoutine::GCAwareJITStubRoutine(
    const MacroAssemblerCodeRef<JITStubRoutinePtrTag>& code, VM& vm)
    : JITStubRoutine(code)
{
    vm.heap.m_jitStubRoutines->add(this);
}

GCAwareJITStubRoutine::~GCAwareJITStubRoutine() { }

void GCAwareJITStubRoutine::observeZeroRefCount()
{
    if (m_isJettisoned) {
        // This case is needed for when the system shuts down. It may be that
        // the JIT stub routine set gets deleted before we get around to deleting
        // this guy. In that case the GC informs us that we're jettisoned already
        // and that we should delete ourselves as soon as the ref count reaches
        // zero.
        delete this;
        return;
    }
    
    RELEASE_ASSERT(!m_refCount);

    m_isJettisoned = true;
}

void GCAwareJITStubRoutine::deleteFromGC()
{
    ASSERT(m_isJettisoned);
    ASSERT(!m_refCount);
    ASSERT(!m_mayBeExecuting);
    
    delete this;
}

void GCAwareJITStubRoutine::markRequiredObjectsInternal(SlotVisitor&)
{
}

MarkingGCAwareJITStubRoutine::MarkingGCAwareJITStubRoutine(
    const MacroAssemblerCodeRef<JITStubRoutinePtrTag>& code, VM& vm, const JSCell* owner,
    const Vector<JSCell*>& cells, Bag<CallLinkInfo>&& callLinkInfos)
    : GCAwareJITStubRoutine(code, vm)
    , m_cells(cells.size())
    , m_callLinkInfos(WTFMove(callLinkInfos))
{
    for (unsigned i = cells.size(); i--;)
        m_cells[i].set(vm, owner, cells[i]);
}

MarkingGCAwareJITStubRoutine::~MarkingGCAwareJITStubRoutine()
{
}

void MarkingGCAwareJITStubRoutine::markRequiredObjectsInternal(SlotVisitor& visitor)
{
    for (auto& entry : m_cells)
        visitor.append(entry);
}


GCAwareJITStubRoutineWithExceptionHandler::GCAwareJITStubRoutineWithExceptionHandler(
    const MacroAssemblerCodeRef<JITStubRoutinePtrTag>& code, VM& vm,  const JSCell* owner, const Vector<JSCell*>& cells, Bag<CallLinkInfo>&& callLinkInfos,
    CodeBlock* codeBlockForExceptionHandlers, DisposableCallSiteIndex exceptionHandlerCallSiteIndex)
    : MarkingGCAwareJITStubRoutine(code, vm, owner, cells, WTFMove(callLinkInfos))
    , m_codeBlockWithExceptionHandler(codeBlockForExceptionHandlers)
#if ENABLE(DFG_JIT)
    , m_codeOriginPool(&m_codeBlockWithExceptionHandler->codeOrigins())
#endif
    , m_exceptionHandlerCallSiteIndex(exceptionHandlerCallSiteIndex)
{
    RELEASE_ASSERT(m_codeBlockWithExceptionHandler);
    ASSERT(!!m_codeBlockWithExceptionHandler->handlerForIndex(exceptionHandlerCallSiteIndex.bits()));
}

GCAwareJITStubRoutineWithExceptionHandler::~GCAwareJITStubRoutineWithExceptionHandler()
{
#if ENABLE(DFG_JIT)
    // We delay deallocation of m_exceptionHandlerCallSiteIndex until GCAwareJITStubRoutineWithExceptionHandler gets destroyed.
    // This means that CallSiteIndex can be reserved correctly so long as the code owned by GCAwareJITStubRoutineWithExceptionHandler is on the stack.
    // This is important since CallSite can be queried so long as this code is on the stack: StackVisitor can retreive CallSiteIndex from the stack.
    ASSERT(!isCompilationThread() && !Thread::mayBeGCThread());
    if (m_codeOriginPool)
        m_codeOriginPool->removeDisposableCallSiteIndex(m_exceptionHandlerCallSiteIndex);
#endif
}

void GCAwareJITStubRoutineWithExceptionHandler::aboutToDie()
{
    m_codeBlockWithExceptionHandler = nullptr;
#if ENABLE(DFG_JIT)
    m_codeOriginPool = nullptr;
#endif
}

void GCAwareJITStubRoutineWithExceptionHandler::observeZeroRefCount()
{
#if ENABLE(DFG_JIT)
    if (m_codeBlockWithExceptionHandler) {
        m_codeBlockWithExceptionHandler->removeExceptionHandlerForCallSite(m_exceptionHandlerCallSiteIndex);
        m_codeBlockWithExceptionHandler = nullptr;
    }
#endif

    Base::observeZeroRefCount();
}


Ref<JITStubRoutine> createJITStubRoutine(
    const MacroAssemblerCodeRef<JITStubRoutinePtrTag>& code,
    VM& vm,
    const JSCell* owner,
    bool makesCalls,
    const Vector<JSCell*>& cells,
    Bag<CallLinkInfo>&& callLinkInfos,
    CodeBlock* codeBlockForExceptionHandlers,
    DisposableCallSiteIndex exceptionHandlerCallSiteIndex)
{
    if (!makesCalls) {
        // Allocating CallLinkInfos means we should have calls.
        ASSERT(callLinkInfos.isEmpty());
        return adoptRef(*new JITStubRoutine(code));
    }
    
    if (codeBlockForExceptionHandlers) {
        RELEASE_ASSERT(JITCode::isOptimizingJIT(codeBlockForExceptionHandlers->jitType()));
        return adoptRef(*new GCAwareJITStubRoutineWithExceptionHandler(code, vm, owner, cells, WTFMove(callLinkInfos), codeBlockForExceptionHandlers, exceptionHandlerCallSiteIndex));
    }

    if (cells.isEmpty() && callLinkInfos.isEmpty())
        return GCAwareJITStubRoutine::create(code, vm);
    
    return adoptRef(*new MarkingGCAwareJITStubRoutine(code, vm, owner, cells, WTFMove(callLinkInfos)));
}

} // namespace JSC

#endif // ENABLE(JIT)