Source/JavaScriptCore/heap/ConservativeRoots.cpp

/*
 * Copyright (C) 2011, 2016 Apple Inc. All rights reserved.
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#include "config.h"
#include "ConservativeRoots.h"

#include "CodeBlock.h"
#include "CodeBlockSetInlines.h"
#include "HeapUtil.h"
#include "JITStubRoutineSet.h"
#include "JSCast.h"
#include "JSCellInlines.h"
#include "MarkedBlockInlines.h"
#include <wtf/OSAllocator.h>

namespace JSC {

ConservativeRoots::ConservativeRoots(Heap& heap)
    : m_roots(m_inlineRoots)
    , m_size(0)
    , m_capacity(inlineCapacity)
    , m_heap(heap)
{
}

ConservativeRoots::~ConservativeRoots()
{
    if (m_roots != m_inlineRoots)
        OSAllocator::decommitAndRelease(m_roots, m_capacity * sizeof(HeapCell*));
}

void ConservativeRoots::grow()
{
    size_t newCapacity = m_capacity == inlineCapacity ? nonInlineCapacity : m_capacity * 2;
    HeapCell** newRoots = static_cast<HeapCell**>(OSAllocator::reserveAndCommit(newCapacity * sizeof(HeapCell*)));
    memcpy(newRoots, m_roots, m_size * sizeof(HeapCell*));
    if (m_roots != m_inlineRoots)
        OSAllocator::decommitAndRelease(m_roots, m_capacity * sizeof(HeapCell*));
    m_capacity = newCapacity;
    m_roots = newRoots;
}

template<typename MarkHook>
inline void ConservativeRoots::genericAddPointer(void* p, HeapVersion markingVersion, HeapVersion newlyAllocatedVersion, TinyBloomFilter filter, MarkHook& markHook)
{
    p = removeArrayPtrTag(p);
    markHook.mark(p);

    HeapUtil::findGCObjectPointersForMarking(
        m_heap, markingVersion, newlyAllocatedVersion, filter, p,
        [&] (void* p, HeapCell::Kind cellKind) {
            if (isJSCellKind(cellKind))
                markHook.markKnownJSCell(static_cast<JSCell*>(p));
            
            if (m_size == m_capacity)
                grow();
            
            m_roots[m_size++] = bitwise_cast<HeapCell*>(p);
        });
}

template<typename MarkHook>
SUPPRESS_ASAN
void ConservativeRoots::genericAddSpan(void* begin, void* end, MarkHook& markHook)
{
    if (begin > end) {
        void* swapTemp = begin;
        begin = end;
        end = swapTemp;
    }

    RELEASE_ASSERT(isPointerAligned(begin));
    RELEASE_ASSERT(isPointerAligned(end));

    TinyBloomFilter filter = m_heap.objectSpace().blocks().filter(); // Make a local copy of filter to show the compiler it won't alias, and can be register-allocated.
    HeapVersion markingVersion = m_heap.objectSpace().markingVersion();
    HeapVersion newlyAllocatedVersion = m_heap.objectSpace().newlyAllocatedVersion();
    for (char** it = static_cast<char**>(begin); it != static_cast<char**>(end); ++it)
        genericAddPointer(*it, markingVersion, newlyAllocatedVersion, filter, markHook);
}

class DummyMarkHook {
public:
    void mark(void*) { }
    void markKnownJSCell(JSCell*) { }
};

void ConservativeRoots::add(void* begin, void* end)
{
    DummyMarkHook dummy;
    genericAddSpan(begin, end, dummy);
}

class CompositeMarkHook {
public:
    CompositeMarkHook(JITStubRoutineSet& stubRoutines, CodeBlockSet& codeBlocks, const AbstractLocker& locker)
        : m_stubRoutines(stubRoutines)
        , m_codeBlocks(codeBlocks)
        , m_codeBlocksLocker(locker)
    {
    }
    
    void mark(void* address)
    {
        m_stubRoutines.mark(address);
    }
    
    void markKnownJSCell(JSCell* cell)
    {
        if (cell->type() == CodeBlockType)
            m_codeBlocks.mark(m_codeBlocksLocker, jsCast<CodeBlock*>(cell));
    }

private:
    JITStubRoutineSet& m_stubRoutines;
    CodeBlockSet& m_codeBlocks;
    const AbstractLocker& m_codeBlocksLocker;
};

void ConservativeRoots::add(
    void* begin, void* end, JITStubRoutineSet& jitStubRoutines, CodeBlockSet& codeBlocks)
{
    LockHolder locker(codeBlocks.getLock());
    CompositeMarkHook markHook(jitStubRoutines, codeBlocks, locker);
    genericAddSpan(begin, end, markHook);
}

} // namespace JSC