Source/JavaScriptCore/heap/JITStubRoutineSet.cpp

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

#if ENABLE(JIT)

#include "GCAwareJITStubRoutine.h"
#include <algorithm>

namespace JSC {

using WTF::Range;

bool JITStubRoutineSet::s_mayHaveRoutinesToDelete = false;

JITStubRoutineSet::JITStubRoutineSet() { }
JITStubRoutineSet::~JITStubRoutineSet()
{
    for (auto& entry : m_routines) {
        GCAwareJITStubRoutine* routine = entry.routine;
        routine->m_mayBeExecuting = false;
        
        if (!routine->m_isJettisoned) {
            // Inform the deref() routine that it should delete this guy as soon
            // as the ref count reaches zero.
            routine->m_isJettisoned = true;
            continue;
        }
        
        routine->deleteFromGC();
    }
}

void JITStubRoutineSet::add(GCAwareJITStubRoutine* routine)
{
    RELEASE_ASSERT(!isCompilationThread());
    ASSERT(!routine->m_isJettisoned);
    
    m_routines.append(Routine {
        routine->startAddress(),
        routine
    });
}

void JITStubRoutineSet::prepareForConservativeScan()
{
    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()
{
    for (auto& entry : m_routines)
        entry.routine->m_mayBeExecuting = false;
}

void JITStubRoutineSet::markSlow(uintptr_t address)
{
    ASSERT(isJITPC(bitwise_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()) {
                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(Seconds timeSlice)
{
    ASSERT(s_mayHaveRoutinesToDelete);

    MonotonicTime startTime = MonotonicTime::now();
    Seconds elapsedTime;
    constexpr unsigned maxBatchSize = 100;

    unsigned endIndex = m_routines.size();

    // Clear the s_mayHaveRoutinesToDelete flag before we start.
    // Destruction of a MarkingGCAwareJITStubRoutine can trigger more routines
    // to be deleted, and some of those may be the ones we have already iterated
    // pass.
    s_mayHaveRoutinesToDelete = false;

    unsigned srcIndex = 0;
    while (srcIndex < endIndex) {
        unsigned batchSize = std::min<unsigned>(maxBatchSize, endIndex - srcIndex);
        while (batchSize--) {
            Routine routine = m_routines[srcIndex];
            if (!routine.routine->m_isJettisoned || routine.routine->m_mayBeExecuting) {
                srcIndex++;
                continue;
            }
            m_routines[srcIndex] = m_routines[--endIndex];

            routine.routine->deleteFromGC();
        }

        elapsedTime = MonotonicTime::now() - startTime;
        if (elapsedTime > timeSlice) {
            // We timed out. Assume there's more to do, and that we should check
            // again next time slice.
            s_mayHaveRoutinesToDelete = true;
            break;
        }
    }

    m_routines.shrinkCapacity(endIndex);
}

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

#endif // ENABLE(JIT)