Source/JavaScriptCore/heap/JITStubRoutineSet.cpp

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#include "config.h"
#include "JITStubRoutineSet.h"

#include <wtf/TZoneMallocInlines.h>

#if ENABLE(JIT)

#include "GCAwareJITStubRoutine.h"
#include "HeapInlines.h"

WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN

namespace JSC {

WTF_MAKE_TZONE_ALLOCATED_IMPL(JITStubRoutineSet);

JITStubRoutineSet::JITStubRoutineSet() = default;
JITStubRoutineSet::~JITStubRoutineSet()
{
    auto destroyRoutine = [&](GCAwareJITStubRoutine* routine) {
        routine->m_mayBeExecuting = false;

        if (!routine->m_isJettisoned) {
            // Inform the deref() routine that it should delete this stub as soon as the ref count reaches zero.
            routine->m_isJettisoned = true;
            return;
        }

        routine->deleteFromGC();
    };

    for (auto& entry : m_routines)
        destroyRoutine(entry.routine);

    for (auto& routine : m_immutableCodeRoutines)
        destroyRoutine(routine);
}

void JITStubRoutineSet::add(GCAwareJITStubRoutine* routine)
{
    RELEASE_ASSERT(!isCompilationThread());
    ASSERT(!routine->m_isJettisoned);

    if (routine->m_isCodeImmutable) {
        m_immutableCodeRoutines.append(routine);
        return;
    }

    m_routines.append(Routine {
        routine->startAddress(),
        routine
    });
}

void JITStubRoutineSet::prepareForConservativeScan()
{
    // Immutable code routines do not matter.

    if (m_routines.isEmpty()) {
        m_range = Range<uintptr_t> { 0, 0 };
        return;
    }
    std::sort(
        m_routines.begin(), m_routines.end(),
        [&] (const Routine& a, const Routine& b) {
            return a.startAddress < b.startAddress;
        });
    m_range = Range<uintptr_t> {
        m_routines.first().startAddress,
        m_routines.last().routine->endAddress()
    };
}

void JITStubRoutineSet::clearMarks()
{
    // Immutable code routines do not matter.
    for (auto& entry : m_routines)
        entry.routine->m_mayBeExecuting = false;
}

void JITStubRoutineSet::markSlow(uintptr_t address)
{
    ASSERT(isJITPC(std::bit_cast<void*>(address)));
    ASSERT(!m_routines.isEmpty());

    Routine* result = approximateBinarySearch<Routine>(
        m_routines.begin(), m_routines.size(), address,
        [] (const Routine* routine) -> uintptr_t { return routine->startAddress; });
    if (result) {
        auto markIfContained = [&] (const Routine& routine, uintptr_t address) {
            if (routine.startAddress <= address && address < routine.routine->endAddress()) {
                ASSERT(!routine.routine->m_isCodeImmutable);
                routine.routine->m_mayBeExecuting = true;
                return true;
            }
            return false;
        };

        if (result > m_routines.begin()) {
            if (markIfContained(result[-1], address))
                return;
        }
        if (markIfContained(result[0], address))
            return;
        if (result + 1 < m_routines.end()) {
            if (markIfContained(result[1], address))
                return;
        }
    }
}

void JITStubRoutineSet::deleteUnmarkedJettisonedStubRoutines(VM& vm)
{
    ASSERT(vm.heap.isInPhase(CollectorPhase::End));

    auto shouldRemove = [&](GCAwareJITStubRoutine* stub) {
        if (!stub->m_ownerIsDead)
            stub->m_ownerIsDead = stub->removeDeadOwners(vm);

        // If the stub is running right now, we should keep it alive regardless of whether owner CodeBlock gets dead.
        // It is OK since we already marked all the related cells.
        if (stub->m_mayBeExecuting)
            return false;

        // If the stub is already jettisoned, and if it is not executed right now, then we can safely destroy this right now
        // since this is not reachable from dead CodeBlock (in CodeBlock's destructor), plus, this will not be executed later.
        if (stub->m_isJettisoned) {
            stub->deleteFromGC();
            return true;
        }

        // If the owner is already dead, then this stub will not be executed. We should remove this from this set.
        // But we should not call deleteFromGC here since unswept CodeBlock may still hold the reference to this stub.
        if (stub->m_ownerIsDead) {
            // Inform the deref() routine that it should delete this stub as soon as the ref count reaches zero.
            stub->m_isJettisoned = true;
            return true;
        }

        return false;
    };

    m_routines.removeAllMatching([&](auto& entry) {
        return shouldRemove(entry.routine);
    });

    m_immutableCodeRoutines.removeAllMatching([&](auto* stub) {
        return shouldRemove(stub);
    });
}

template<typename Visitor>
void JITStubRoutineSet::traceMarkedStubRoutines(Visitor& visitor)
{
    for (auto& entry : m_routines) {
        GCAwareJITStubRoutine* routine = entry.routine;
        if (!routine->m_mayBeExecuting)
            continue;
        routine->markRequiredObjects(visitor);
    }
}

template void JITStubRoutineSet::traceMarkedStubRoutines(AbstractSlotVisitor&);
template void JITStubRoutineSet::traceMarkedStubRoutines(SlotVisitor&);

} // namespace JSC

WTF_ALLOW_UNSAFE_BUFFER_USAGE_END

#else

namespace JSC {

WTF_MAKE_TZONE_ALLOCATED_IMPL(JITStubRoutineSet);

} // namespace JSC

#endif // ENABLE(JIT)