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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: set ts=8 sts=4 et sw=4 tw=99:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/* JS Garbage Collector. */

#ifndef jsgc_h
#define jsgc_h

#include "mozilla/DebugOnly.h"
#include "mozilla/MemoryReporting.h"

#include "jslock.h"
#include "jsobj.h"

#include "js/GCAPI.h"
#include "js/SliceBudget.h"
#include "js/Vector.h"

class JSAtom;
struct JSCompartment;
class JSFlatString;
class JSLinearString;

namespace js {

class ArgumentsObject;
class ArrayBufferObject;
class ArrayBufferViewObject;
class SharedArrayBufferObject;
class BaseShape;
class DebugScopeObject;
class GCHelperThread;
class GlobalObject;
class LazyScript;
class Nursery;
class PropertyName;
class ScopeObject;
class Shape;
class UnownedBaseShape;

unsigned GetCPUCount();

enum HeapState {
    Idle,             // doing nothing with the GC heap
    Tracing,          // tracing the GC heap without collecting, e.g. IterateCompartments()
    MajorCollecting,  // doing a GC of the major heap
    MinorCollecting   // doing a GC of the minor heap (nursery)
};

namespace jit {
    class JitCode;
}

namespace gc {

enum State {
    NO_INCREMENTAL,
    MARK_ROOTS,
    MARK,
    SWEEP,
    INVALID
};

class ChunkPool {
    Chunk*  emptyChunkListHead;
    size_t  emptyCount;

  public:
    ChunkPool()
      : emptyChunkListHead(nullptr),
        emptyCount(0) { }

    size_t getEmptyCount() const {
        return emptyCount;
    }

    inline bool wantBackgroundAllocation(JSRuntime* rt) const;

    /* Must be called with the GC lock taken. */
    inline Chunk* get(JSRuntime* rt);

    /* Must be called either during the GC or with the GC lock taken. */
    inline void put(Chunk* chunk);

    /*
     * Return the list of chunks that can be released outside the GC lock.
     * Must be called either during the GC or with the GC lock taken.
     */
    Chunk* expire(JSRuntime* rt, bool releaseAll);

    /* Must be called with the GC lock taken. */
    void expireAndFree(JSRuntime* rt, bool releaseAll);
};

static inline JSGCTraceKind
MapAllocToTraceKind(AllocKind kind)
{
    static const JSGCTraceKind map[] = {
        JSTRACE_OBJECT,     /* FINALIZE_OBJECT0 */
        JSTRACE_OBJECT,     /* FINALIZE_OBJECT0_BACKGROUND */
        JSTRACE_OBJECT,     /* FINALIZE_OBJECT2 */
        JSTRACE_OBJECT,     /* FINALIZE_OBJECT2_BACKGROUND */
        JSTRACE_OBJECT,     /* FINALIZE_OBJECT4 */
        JSTRACE_OBJECT,     /* FINALIZE_OBJECT4_BACKGROUND */
        JSTRACE_OBJECT,     /* FINALIZE_OBJECT8 */
        JSTRACE_OBJECT,     /* FINALIZE_OBJECT8_BACKGROUND */
        JSTRACE_OBJECT,     /* FINALIZE_OBJECT12 */
        JSTRACE_OBJECT,     /* FINALIZE_OBJECT12_BACKGROUND */
        JSTRACE_OBJECT,     /* FINALIZE_OBJECT16 */
        JSTRACE_OBJECT,     /* FINALIZE_OBJECT16_BACKGROUND */
        JSTRACE_SCRIPT,     /* FINALIZE_SCRIPT */
        JSTRACE_LAZY_SCRIPT,/* FINALIZE_LAZY_SCRIPT */
        JSTRACE_SHAPE,      /* FINALIZE_SHAPE */
        JSTRACE_BASE_SHAPE, /* FINALIZE_BASE_SHAPE */
        JSTRACE_TYPE_OBJECT,/* FINALIZE_TYPE_OBJECT */
        JSTRACE_STRING,     /* FINALIZE_FAT_INLINE_STRING */
        JSTRACE_STRING,     /* FINALIZE_STRING */
        JSTRACE_STRING,     /* FINALIZE_EXTERNAL_STRING */
        JSTRACE_JITCODE,    /* FINALIZE_JITCODE */
    };
    JS_STATIC_ASSERT(JS_ARRAY_LENGTH(map) == FINALIZE_LIMIT);
    return map[kind];
}

template <typename T> struct MapTypeToTraceKind {};
template <> struct MapTypeToTraceKind<ObjectImpl>       { static const JSGCTraceKind kind = JSTRACE_OBJECT; };
template <> struct MapTypeToTraceKind<JSObject>         { static const JSGCTraceKind kind = JSTRACE_OBJECT; };
template <> struct MapTypeToTraceKind<JSFunction>       { static const JSGCTraceKind kind = JSTRACE_OBJECT; };
template <> struct MapTypeToTraceKind<ArgumentsObject>  { static const JSGCTraceKind kind = JSTRACE_OBJECT; };
template <> struct MapTypeToTraceKind<ArrayBufferObject>{ static const JSGCTraceKind kind = JSTRACE_OBJECT; };
template <> struct MapTypeToTraceKind<ArrayBufferViewObject>{ static const JSGCTraceKind kind = JSTRACE_OBJECT; };
template <> struct MapTypeToTraceKind<SharedArrayBufferObject>{ static const JSGCTraceKind kind = JSTRACE_OBJECT; };
template <> struct MapTypeToTraceKind<DebugScopeObject> { static const JSGCTraceKind kind = JSTRACE_OBJECT; };
template <> struct MapTypeToTraceKind<GlobalObject>     { static const JSGCTraceKind kind = JSTRACE_OBJECT; };
template <> struct MapTypeToTraceKind<ScopeObject>      { static const JSGCTraceKind kind = JSTRACE_OBJECT; };
template <> struct MapTypeToTraceKind<JSScript>         { static const JSGCTraceKind kind = JSTRACE_SCRIPT; };
template <> struct MapTypeToTraceKind<LazyScript>       { static const JSGCTraceKind kind = JSTRACE_LAZY_SCRIPT; };
template <> struct MapTypeToTraceKind<Shape>            { static const JSGCTraceKind kind = JSTRACE_SHAPE; };
template <> struct MapTypeToTraceKind<BaseShape>        { static const JSGCTraceKind kind = JSTRACE_BASE_SHAPE; };
template <> struct MapTypeToTraceKind<UnownedBaseShape> { static const JSGCTraceKind kind = JSTRACE_BASE_SHAPE; };
template <> struct MapTypeToTraceKind<types::TypeObject>{ static const JSGCTraceKind kind = JSTRACE_TYPE_OBJECT; };
template <> struct MapTypeToTraceKind<JSAtom>           { static const JSGCTraceKind kind = JSTRACE_STRING; };
template <> struct MapTypeToTraceKind<JSString>         { static const JSGCTraceKind kind = JSTRACE_STRING; };
template <> struct MapTypeToTraceKind<JSFlatString>     { static const JSGCTraceKind kind = JSTRACE_STRING; };
template <> struct MapTypeToTraceKind<JSLinearString>   { static const JSGCTraceKind kind = JSTRACE_STRING; };
template <> struct MapTypeToTraceKind<PropertyName>     { static const JSGCTraceKind kind = JSTRACE_STRING; };
template <> struct MapTypeToTraceKind<jit::JitCode>     { static const JSGCTraceKind kind = JSTRACE_JITCODE; };

/* Map from C++ type to finalize kind. JSObject does not have a 1:1 mapping, so must use Arena::thingSize. */
template <typename T> struct MapTypeToFinalizeKind {};
template <> struct MapTypeToFinalizeKind<JSScript>          { static const AllocKind kind = FINALIZE_SCRIPT; };
template <> struct MapTypeToFinalizeKind<LazyScript>        { static const AllocKind kind = FINALIZE_LAZY_SCRIPT; };
template <> struct MapTypeToFinalizeKind<Shape>             { static const AllocKind kind = FINALIZE_SHAPE; };
template <> struct MapTypeToFinalizeKind<BaseShape>         { static const AllocKind kind = FINALIZE_BASE_SHAPE; };
template <> struct MapTypeToFinalizeKind<types::TypeObject> { static const AllocKind kind = FINALIZE_TYPE_OBJECT; };
template <> struct MapTypeToFinalizeKind<JSFatInlineString> { static const AllocKind kind = FINALIZE_FAT_INLINE_STRING; };
template <> struct MapTypeToFinalizeKind<JSString>          { static const AllocKind kind = FINALIZE_STRING; };
template <> struct MapTypeToFinalizeKind<JSExternalString>  { static const AllocKind kind = FINALIZE_EXTERNAL_STRING; };
template <> struct MapTypeToFinalizeKind<jit::JitCode>      { static const AllocKind kind = FINALIZE_JITCODE; };

#if defined(JSGC_GENERATIONAL) || defined(DEBUG)
static inline bool
IsNurseryAllocable(AllocKind kind)
{
    JS_ASSERT(kind >= 0 && unsigned(kind) < FINALIZE_LIMIT);
    static const bool map[] = {
        false,     /* FINALIZE_OBJECT0 */
        true,      /* FINALIZE_OBJECT0_BACKGROUND */
        false,     /* FINALIZE_OBJECT2 */
        true,      /* FINALIZE_OBJECT2_BACKGROUND */
        false,     /* FINALIZE_OBJECT4 */
        true,      /* FINALIZE_OBJECT4_BACKGROUND */
        false,     /* FINALIZE_OBJECT8 */
        true,      /* FINALIZE_OBJECT8_BACKGROUND */
        false,     /* FINALIZE_OBJECT12 */
        true,      /* FINALIZE_OBJECT12_BACKGROUND */
        false,     /* FINALIZE_OBJECT16 */
        true,      /* FINALIZE_OBJECT16_BACKGROUND */
        false,     /* FINALIZE_SCRIPT */
        false,     /* FINALIZE_LAZY_SCRIPT */
        false,     /* FINALIZE_SHAPE */
        false,     /* FINALIZE_BASE_SHAPE */
        false,     /* FINALIZE_TYPE_OBJECT */
        false,     /* FINALIZE_FAT_INLINE_STRING */
        false,     /* FINALIZE_STRING */
        false,     /* FINALIZE_EXTERNAL_STRING */
        false,     /* FINALIZE_JITCODE */
    };
    JS_STATIC_ASSERT(JS_ARRAY_LENGTH(map) == FINALIZE_LIMIT);
    return map[kind];
}
#endif

static inline bool
IsBackgroundFinalized(AllocKind kind)
{
    JS_ASSERT(kind >= 0 && unsigned(kind) < FINALIZE_LIMIT);
    static const bool map[] = {
        false,     /* FINALIZE_OBJECT0 */
        true,      /* FINALIZE_OBJECT0_BACKGROUND */
        false,     /* FINALIZE_OBJECT2 */
        true,      /* FINALIZE_OBJECT2_BACKGROUND */
        false,     /* FINALIZE_OBJECT4 */
        true,      /* FINALIZE_OBJECT4_BACKGROUND */
        false,     /* FINALIZE_OBJECT8 */
        true,      /* FINALIZE_OBJECT8_BACKGROUND */
        false,     /* FINALIZE_OBJECT12 */
        true,      /* FINALIZE_OBJECT12_BACKGROUND */
        false,     /* FINALIZE_OBJECT16 */
        true,      /* FINALIZE_OBJECT16_BACKGROUND */
        false,     /* FINALIZE_SCRIPT */
        false,     /* FINALIZE_LAZY_SCRIPT */
        true,      /* FINALIZE_SHAPE */
        true,      /* FINALIZE_BASE_SHAPE */
        true,      /* FINALIZE_TYPE_OBJECT */
        true,      /* FINALIZE_FAT_INLINE_STRING */
        true,      /* FINALIZE_STRING */
        false,     /* FINALIZE_EXTERNAL_STRING */
        false,     /* FINALIZE_JITCODE */
    };
    JS_STATIC_ASSERT(JS_ARRAY_LENGTH(map) == FINALIZE_LIMIT);
    return map[kind];
}

static inline bool
CanBeFinalizedInBackground(gc::AllocKind kind, const Class* clasp)
{
    JS_ASSERT(kind <= gc::FINALIZE_OBJECT_LAST);
    /* If the class has no finalizer or a finalizer that is safe to call on
     * a different thread, we change the finalize kind. For example,
     * FINALIZE_OBJECT0 calls the finalizer on the main thread,
     * FINALIZE_OBJECT0_BACKGROUND calls the finalizer on the gcHelperThread.
     * IsBackgroundFinalized is called to prevent recursively incrementing
     * the finalize kind; kind may already be a background finalize kind.
     */
    return (!gc::IsBackgroundFinalized(kind) &&
            (!clasp->finalize || (clasp->flags & JSCLASS_BACKGROUND_FINALIZE)));
}

inline JSGCTraceKind
GetGCThingTraceKind(const void* thing);

/* Capacity for slotsToThingKind */
const size_t SLOTS_TO_THING_KIND_LIMIT = 17;

extern const AllocKind slotsToThingKind[];

/* Get the best kind to use when making an object with the given slot count. */
static inline AllocKind
GetGCObjectKind(size_t numSlots)
{
    if (numSlots >= SLOTS_TO_THING_KIND_LIMIT)
        return FINALIZE_OBJECT16;
    return slotsToThingKind[numSlots];
}

/* As for GetGCObjectKind, but for dense array allocation. */
static inline AllocKind
GetGCArrayKind(size_t numSlots)
{
    /*
     * Dense arrays can use their fixed slots to hold their elements array
     * (less two Values worth of ObjectElements header), but if more than the
     * maximum number of fixed slots is needed then the fixed slots will be
     * unused.
     */
    JS_STATIC_ASSERT(ObjectElements::VALUES_PER_HEADER == 2);
    if (numSlots > JSObject::NELEMENTS_LIMIT || numSlots + 2 >= SLOTS_TO_THING_KIND_LIMIT)
        return FINALIZE_OBJECT2;
    return slotsToThingKind[numSlots + 2];
}

static inline AllocKind
GetGCObjectFixedSlotsKind(size_t numFixedSlots)
{
    JS_ASSERT(numFixedSlots < SLOTS_TO_THING_KIND_LIMIT);
    return slotsToThingKind[numFixedSlots];
}

static inline AllocKind
GetBackgroundAllocKind(AllocKind kind)
{
    JS_ASSERT(!IsBackgroundFinalized(kind));
    JS_ASSERT(kind <= FINALIZE_OBJECT_LAST);
    return (AllocKind) (kind + 1);
}

/*
 * Try to get the next larger size for an object, keeping BACKGROUND
 * consistent.
 */
static inline bool
TryIncrementAllocKind(AllocKind* kindp)
{
    size_t next = size_t(*kindp) + 2;
    if (next >= size_t(FINALIZE_OBJECT_LIMIT))
        return false;
    *kindp = AllocKind(next);
    return true;
}

/* Get the number of fixed slots and initial capacity associated with a kind. */
static inline size_t
GetGCKindSlots(AllocKind thingKind)
{
    /* Using a switch in hopes that thingKind will usually be a compile-time constant. */
    switch (thingKind) {
      case FINALIZE_OBJECT0:
      case FINALIZE_OBJECT0_BACKGROUND:
        return 0;
      case FINALIZE_OBJECT2:
      case FINALIZE_OBJECT2_BACKGROUND:
        return 2;
      case FINALIZE_OBJECT4:
      case FINALIZE_OBJECT4_BACKGROUND:
        return 4;
      case FINALIZE_OBJECT8:
      case FINALIZE_OBJECT8_BACKGROUND:
        return 8;
      case FINALIZE_OBJECT12:
      case FINALIZE_OBJECT12_BACKGROUND:
        return 12;
      case FINALIZE_OBJECT16:
      case FINALIZE_OBJECT16_BACKGROUND:
        return 16;
      default:
        MOZ_ASSUME_UNREACHABLE("Bad object finalize kind");
    }
}

static inline size_t
GetGCKindSlots(AllocKind thingKind, const Class* clasp)
{
    size_t nslots = GetGCKindSlots(thingKind);

    /* An object's private data uses the space taken by its last fixed slot. */
    if (clasp->flags & JSCLASS_HAS_PRIVATE) {
        JS_ASSERT(nslots > 0);
        nslots--;
    }

    /*
     * Functions have a larger finalize kind than FINALIZE_OBJECT to reserve
     * space for the extra fields in JSFunction, but have no fixed slots.
     */
    if (clasp == FunctionClassPtr)
        nslots = 0;

    return nslots;
}

/*
 * ArenaList::head points to the start of the list. Normally cursor points
 * to the first arena in the list with some free things and all arenas
 * before cursor are fully allocated. However, as the arena currently being
 * allocated from is considered full while its list of free spans is moved
 * into the freeList, during the GC or cell enumeration, when an
 * unallocated freeList is moved back to the arena, we can see an arena
 * with some free cells before the cursor. The cursor is an indirect
 * pointer to allow for efficient list insertion at the cursor point and
 * other list manipulations.
 */
struct ArenaList {
    ArenaHeader*    head;
    ArenaHeader**   cursor;

    ArenaList() {
        clear();
    }

    void clear() {
        head = nullptr;
        cursor = &head;
    }

    void insert(ArenaHeader* arena);
};

class ArenaLists
{
    /*
     * For each arena kind its free list is represented as the first span with
     * free things. Initially all the spans are initialized as empty. After we
     * find a new arena with available things we move its first free span into
     * the list and set the arena as fully allocated. way we do not need to
     * update the arena header after the initial allocation. When starting the
     * GC we only move the head of the of the list of spans back to the arena
     * only for the arena that was not fully allocated.
     */
    FreeSpan       freeLists[FINALIZE_LIMIT];

    ArenaList      arenaLists[FINALIZE_LIMIT];

    /*
     * The background finalization adds the finalized arenas to the list at
     * the *cursor position. backgroundFinalizeState controls the interaction
     * between the GC lock and the access to the list from the allocation
     * thread.
     *
     * BFS_DONE indicates that the finalizations is not running or cannot
     * affect this arena list. The allocation thread can access the list
     * outside the GC lock.
     *
     * In BFS_RUN and BFS_JUST_FINISHED the allocation thread must take the
     * lock. The former indicates that the finalization still runs. The latter
     * signals that finalization just added to the list finalized arenas. In
     * that case the lock effectively serves as a read barrier to ensure that
     * the allocation thread see all the writes done during finalization.
     */
    enum BackgroundFinalizeState {
        BFS_DONE,
        BFS_RUN,
        BFS_JUST_FINISHED
    };

    volatile uintptr_t backgroundFinalizeState[FINALIZE_LIMIT];

  public:
    /* For each arena kind, a list of arenas remaining to be swept. */
    ArenaHeader* arenaListsToSweep[FINALIZE_LIMIT];

    /* Shape arenas to be swept in the foreground. */
    ArenaHeader* gcShapeArenasToSweep;

  public:
    ArenaLists() {
        for (size_t i = 0; i != FINALIZE_LIMIT; ++i)
            freeLists[i].initAsEmpty();
        for (size_t i = 0; i != FINALIZE_LIMIT; ++i)
            backgroundFinalizeState[i] = BFS_DONE;
        for (size_t i = 0; i != FINALIZE_LIMIT; ++i)
            arenaListsToSweep[i] = nullptr;
        gcShapeArenasToSweep = nullptr;
    }

    ~ArenaLists() {
        for (size_t i = 0; i != FINALIZE_LIMIT; ++i) {
            /*
             * We can only call this during the shutdown after the last GC when
             * the background finalization is disabled.
             */
            JS_ASSERT(backgroundFinalizeState[i] == BFS_DONE);
            ArenaHeader** headp = &arenaLists[i].head;
            while (ArenaHeader* aheader = *headp) {
                *headp = aheader->next;
                aheader->chunk()->releaseArena(aheader);
            }
        }
    }

    static uintptr_t getFreeListOffset(AllocKind thingKind) {
        uintptr_t offset = offsetof(ArenaLists, freeLists);
        return offset + thingKind * sizeof(FreeSpan);
    }

    const FreeSpan* getFreeList(AllocKind thingKind) const {
        return &freeLists[thingKind];
    }

    ArenaHeader* getFirstArena(AllocKind thingKind) const {
        return arenaLists[thingKind].head;
    }

    ArenaHeader* getFirstArenaToSweep(AllocKind thingKind) const {
        return arenaListsToSweep[thingKind];
    }

    bool arenaListsAreEmpty() const {
        for (size_t i = 0; i != FINALIZE_LIMIT; ++i) {
            /*
             * The arena cannot be empty if the background finalization is not yet
             * done.
             */
            if (backgroundFinalizeState[i] != BFS_DONE)
                return false;
            if (arenaLists[i].head)
                return false;
        }
        return true;
    }

    bool arenasAreFull(AllocKind thingKind) const {
        return !*arenaLists[thingKind].cursor;
    }

    void unmarkAll() {
        for (size_t i = 0; i != FINALIZE_LIMIT; ++i) {
            /* The background finalization must have stopped at this point. */
            JS_ASSERT(backgroundFinalizeState[i] == BFS_DONE ||
                      backgroundFinalizeState[i] == BFS_JUST_FINISHED);
            for (ArenaHeader* aheader = arenaLists[i].head; aheader; aheader = aheader->next) {
                uintptr_t* word = aheader->chunk()->bitmap.arenaBits(aheader);
                memset(word, 0, ArenaBitmapWords * sizeof(uintptr_t));
            }
        }
    }

    bool doneBackgroundFinalize(AllocKind kind) const {
        return backgroundFinalizeState[kind] == BFS_DONE ||
               backgroundFinalizeState[kind] == BFS_JUST_FINISHED;
    }

    bool needBackgroundFinalizeWait(AllocKind kind) const {
        return backgroundFinalizeState[kind] != BFS_DONE;
    }

    /*
     * Return the free list back to the arena so the GC finalization will not
     * run the finalizers over unitialized bytes from free things.
     */
    void purge() {
        for (size_t i = 0; i != FINALIZE_LIMIT; ++i)
            purge(AllocKind(i));
    }

    void purge(AllocKind i) {
        FreeSpan* headSpan = &freeLists[i];
        if (!headSpan->isEmpty()) {
            ArenaHeader* aheader = headSpan->arenaHeader();
            aheader->setFirstFreeSpan(headSpan);
            headSpan->initAsEmpty();
        }
    }

    inline void prepareForIncrementalGC(JSRuntime* rt);

    /*
     * Temporarily copy the free list heads to the arenas so the code can see
     * the proper value in ArenaHeader::freeList when accessing the latter
     * outside the GC.
     */
    void copyFreeListsToArenas() {
        for (size_t i = 0; i != FINALIZE_LIMIT; ++i)
            copyFreeListToArena(AllocKind(i));
    }

    void copyFreeListToArena(AllocKind thingKind) {
        FreeSpan* headSpan = &freeLists[thingKind];
        if (!headSpan->isEmpty()) {
            ArenaHeader* aheader = headSpan->arenaHeader();
            JS_ASSERT(!aheader->hasFreeThings());
            aheader->setFirstFreeSpan(headSpan);
        }
    }

    /*
     * Clear the free lists in arenas that were temporarily set there using
     * copyToArenas.
     */
    void clearFreeListsInArenas() {
        for (size_t i = 0; i != FINALIZE_LIMIT; ++i)
            clearFreeListInArena(AllocKind(i));
    }


    void clearFreeListInArena(AllocKind kind) {
        FreeSpan* headSpan = &freeLists[kind];
        if (!headSpan->isEmpty()) {
            ArenaHeader* aheader = headSpan->arenaHeader();
            JS_ASSERT(aheader->getFirstFreeSpan().isSameNonEmptySpan(headSpan));
            aheader->setAsFullyUsed();
        }
    }

    /*
     * Check that the free list is either empty or were synchronized with the
     * arena using copyToArena().
     */
    bool isSynchronizedFreeList(AllocKind kind) {
        FreeSpan* headSpan = &freeLists[kind];
        if (headSpan->isEmpty())
            return true;
        ArenaHeader* aheader = headSpan->arenaHeader();
        if (aheader->hasFreeThings()) {
            /*
             * If the arena has a free list, it must be the same as one in
             * lists.
             */
            JS_ASSERT(aheader->getFirstFreeSpan().isSameNonEmptySpan(headSpan));
            return true;
        }
        return false;
    }

    MOZ_ALWAYS_INLINE void* allocateFromFreeList(AllocKind thingKind, size_t thingSize) {
        return freeLists[thingKind].allocate(thingSize);
    }

    template <AllowGC allowGC>
    static void* refillFreeList(ThreadSafeContext* cx, AllocKind thingKind);

    /*
     * Moves all arenas from |fromArenaLists| into |this|.  In
     * parallel blocks, we temporarily create one ArenaLists per
     * parallel thread.  When the parallel block ends, we move
     * whatever allocations may have been performed back into the
     * compartment's main arena list using this function.
     */
    void adoptArenas(JSRuntime* runtime, ArenaLists* fromArenaLists);

    /* True if the ArenaHeader in question is found in this ArenaLists */
    bool containsArena(JSRuntime* runtime, ArenaHeader* arenaHeader);

    void checkEmptyFreeLists() {
#ifdef DEBUG
        for (size_t i = 0; i < mozilla::ArrayLength(freeLists); ++i)
            JS_ASSERT(freeLists[i].isEmpty());
#endif
    }

    void checkEmptyFreeList(AllocKind kind) {
        JS_ASSERT(freeLists[kind].isEmpty());
    }

    void queueObjectsForSweep(FreeOp* fop);
    void queueStringsForSweep(FreeOp* fop);
    void queueShapesForSweep(FreeOp* fop);
    void queueScriptsForSweep(FreeOp* fop);
    void queueJitCodeForSweep(FreeOp* fop);

    bool foregroundFinalize(FreeOp* fop, AllocKind thingKind, SliceBudget& sliceBudget);
    static void backgroundFinalize(FreeOp* fop, ArenaHeader* listHead, bool onBackgroundThread);

    void wipeDuringParallelExecution(JSRuntime* rt);

  private:
    inline void finalizeNow(FreeOp* fop, AllocKind thingKind);
    inline void forceFinalizeNow(FreeOp* fop, AllocKind thingKind);
    inline void queueForForegroundSweep(FreeOp* fop, AllocKind thingKind);
    inline void queueForBackgroundSweep(FreeOp* fop, AllocKind thingKind);

    void* allocateFromArena(JS::Zone* zone, AllocKind thingKind);
    inline void* allocateFromArenaInline(JS::Zone* zone, AllocKind thingKind);

    inline void normalizeBackgroundFinalizeState(AllocKind thingKind);

    friend class js::Nursery;
};

/*
 * Initial allocation size for data structures holding chunks is set to hold
 * chunks with total capacity of 16MB to avoid buffer resizes during browser
 * startup.
 */
const size_t INITIAL_CHUNK_CAPACITY = 16 * 1024 * 1024 / ChunkSize;

/* The number of GC cycles an empty chunk can survive before been released. */
const size_t MAX_EMPTY_CHUNK_AGE = 4;

} /* namespace gc */

typedef enum JSGCRootType {
    JS_GC_ROOT_VALUE_PTR,
    JS_GC_ROOT_STRING_PTR,
    JS_GC_ROOT_OBJECT_PTR,
    JS_GC_ROOT_SCRIPT_PTR
} JSGCRootType;

struct RootInfo {
    RootInfo() {}
    RootInfo(const char* name, JSGCRootType type) : name(name), type(type) {}
    const char* name;
    JSGCRootType type;
};

typedef js::HashMap<void*,
                    RootInfo,
                    js::DefaultHasher<void*>,
                    js::SystemAllocPolicy> RootedValueMap;

extern bool
AddValueRoot(JSContext* cx, js::Value* vp, const char* name);

extern bool
AddValueRootRT(JSRuntime* rt, js::Value* vp, const char* name);

extern bool
AddStringRoot(JSContext* cx, JSString** rp, const char* name);

extern bool
AddObjectRoot(JSContext* cx, JSObject** rp, const char* name);

extern bool
AddObjectRoot(JSRuntime* rt, JSObject** rp, const char* name);

extern bool
AddScriptRoot(JSContext* cx, JSScript** rp, const char* name);

extern void
RemoveRoot(JSRuntime* rt, void* rp);

} /* namespace js */

extern bool
js_InitGC(JSRuntime* rt, uint32_t maxbytes);

extern void
js_FinishGC(JSRuntime* rt);

namespace js {

class InterpreterFrame;

extern void
MarkCompartmentActive(js::InterpreterFrame* fp);

extern void
TraceRuntime(JSTracer* trc);

/* Must be called with GC lock taken. */
extern bool
TriggerGC(JSRuntime* rt, JS::gcreason::Reason reason);

/* Must be called with GC lock taken. */
extern bool
TriggerZoneGC(Zone* zone, JS::gcreason::Reason reason);

extern void
MaybeGC(JSContext* cx);

extern void
ReleaseAllJITCode(FreeOp* op);

/*
 * Kinds of js_GC invocation.
 */
typedef enum JSGCInvocationKind {
    /* Normal invocation. */
    GC_NORMAL           = 0,

    /* Minimize GC triggers and release empty GC chunks right away. */
    GC_SHRINK             = 1
} JSGCInvocationKind;

extern void
GC(JSRuntime* rt, JSGCInvocationKind gckind, JS::gcreason::Reason reason);

extern void
GCSlice(JSRuntime* rt, JSGCInvocationKind gckind, JS::gcreason::Reason reason, int64_t millis = 0);

extern void
GCFinalSlice(JSRuntime* rt, JSGCInvocationKind gckind, JS::gcreason::Reason reason);

extern void
GCDebugSlice(JSRuntime* rt, bool limit, int64_t objCount);

extern void
PrepareForDebugGC(JSRuntime* rt);

extern void
MinorGC(JSRuntime* rt, JS::gcreason::Reason reason);

extern void
MinorGC(JSContext* cx, JS::gcreason::Reason reason);

#ifdef JS_GC_ZEAL
extern void
SetGCZeal(JSRuntime* rt, uint8_t zeal, uint32_t frequency);
#endif

/* Functions for managing cross compartment gray pointers. */

extern void
DelayCrossCompartmentGrayMarking(JSObject* src);

extern void
NotifyGCNukeWrapper(JSObject* o);

extern unsigned
NotifyGCPreSwap(JSObject* a, JSObject* b);

extern void
NotifyGCPostSwap(JSObject* a, JSObject* b, unsigned preResult);

/*
 * Helper that implements sweeping and allocation for kinds that can be swept
 * and allocated off the main thread.
 *
 * In non-threadsafe builds, all actual sweeping and allocation is performed
 * on the main thread, but GCHelperThread encapsulates this from clients as
 * much as possible.
 */
class GCHelperThread {
    enum State {
        IDLE,
        SWEEPING,
        ALLOCATING,
        CANCEL_ALLOCATION,
        SHUTDOWN
    };

    /*
     * During the finalization we do not free immediately. Rather we add the
     * corresponding pointers to a buffer which we later release on a
     * separated thread.
     *
     * The buffer is implemented as a vector of 64K arrays of pointers, not as
     * a simple vector, to avoid realloc calls during the vector growth and to
     * not bloat the binary size of the inlined freeLater method. Any OOM
     * during buffer growth results in the pointer being freed immediately.
     */
    static const size_t FREE_ARRAY_SIZE = size_t(1) << 16;
    static const size_t FREE_ARRAY_LENGTH = FREE_ARRAY_SIZE / sizeof(void*);

    JSRuntime*        const rt;
    PRThread*         thread;
    PRCondVar*        wakeup;
    PRCondVar*        done;
    volatile State    state;

    void wait(PRCondVar* which);

    bool              sweepFlag;
    bool              shrinkFlag;

    Vector<void**, 16, js::SystemAllocPolicy> freeVector;
    void**          freeCursor;
    void**          freeCursorEnd;

    bool              backgroundAllocation;

    friend class js::gc::ArenaLists;

    void
    replenishAndFreeLater(void* ptr);

    static void freeElementsAndArray(void** array, void** end) {
        JS_ASSERT(array <= end);
        for (void** p = array; p != end; ++p)
            js_free(*p);
        js_free(array);
    }

    static void threadMain(void* arg);
    void threadLoop();

    /* Must be called with the GC lock taken. */
    void doSweep();

  public:
    GCHelperThread(JSRuntime* rt)
      : rt(rt),
        thread(nullptr),
        wakeup(nullptr),
        done(nullptr),
        state(IDLE),
        sweepFlag(false),
        shrinkFlag(false),
        freeCursor(nullptr),
        freeCursorEnd(nullptr),
        backgroundAllocation(true)
    { }

    bool init();
    void finish();

    /* Must be called with the GC lock taken. */
    void startBackgroundSweep(bool shouldShrink);

    /* Must be called with the GC lock taken. */
    void startBackgroundShrink();

    /* Must be called without the GC lock taken. */
    void waitBackgroundSweepEnd();

    /* Must be called without the GC lock taken. */
    void waitBackgroundSweepOrAllocEnd();

    /* Must be called with the GC lock taken. */
    inline void startBackgroundAllocationIfIdle();

    bool canBackgroundAllocate() const {
        return backgroundAllocation;
    }

    void disableBackgroundAllocation() {
        backgroundAllocation = false;
    }

    PRThread* getThread() const {
        return thread;
    }

    bool onBackgroundThread();

    /*
     * Outside the GC lock may give true answer when in fact the sweeping has
     * been done.
     */
    bool sweeping() const {
        return state == SWEEPING;
    }

    bool shouldShrink() const {
        JS_ASSERT(sweeping());
        return shrinkFlag;
    }

    void freeLater(void* ptr) {
        JS_ASSERT(!sweeping());
        if (freeCursor != freeCursorEnd)
            *freeCursor++ = ptr;
        else
            replenishAndFreeLater(ptr);
    }
};

struct GCChunkHasher {
    typedef gc::Chunk* Lookup;

    /*
     * Strip zeros for better distribution after multiplying by the golden
     * ratio.
     */
    static HashNumber hash(gc::Chunk* chunk) {
        JS_ASSERT(!(uintptr_t(chunk) & gc::ChunkMask));
        return HashNumber(uintptr_t(chunk) >> gc::ChunkShift);
    }

    static bool match(gc::Chunk* k, gc::Chunk* l) {
        JS_ASSERT(!(uintptr_t(k) & gc::ChunkMask));
        JS_ASSERT(!(uintptr_t(l) & gc::ChunkMask));
        return k == l;
    }
};

typedef HashSet<js::gc::Chunk*, GCChunkHasher, SystemAllocPolicy> GCChunkSet;

struct GrayRoot {
    void* thing;
    JSGCTraceKind kind;
#ifdef DEBUG
    JSTraceNamePrinter debugPrinter;
    const void* debugPrintArg;
    size_t debugPrintIndex;
#endif

    GrayRoot(void* thing, JSGCTraceKind kind)
        : thing(thing), kind(kind) {}
};

void
MarkStackRangeConservatively(JSTracer* trc, Value* begin, Value* end);

typedef void (*IterateChunkCallback)(JSRuntime* rt, void* data, gc::Chunk* chunk);
typedef void (*IterateZoneCallback)(JSRuntime* rt, void* data, JS::Zone* zone);
typedef void (*IterateArenaCallback)(JSRuntime* rt, void* data, gc::Arena* arena,
                                     JSGCTraceKind traceKind, size_t thingSize);
typedef void (*IterateCellCallback)(JSRuntime* rt, void* data, void* thing,
                                    JSGCTraceKind traceKind, size_t thingSize);

/*
 * This function calls |zoneCallback| on every zone, |compartmentCallback| on
 * every compartment, |arenaCallback| on every in-use arena, and |cellCallback|
 * on every in-use cell in the GC heap.
 */
extern void
IterateZonesCompartmentsArenasCells(JSRuntime* rt, void* data,
                                    IterateZoneCallback zoneCallback,
                                    JSIterateCompartmentCallback compartmentCallback,
                                    IterateArenaCallback arenaCallback,
                                    IterateCellCallback cellCallback);

/*
 * This function is like IterateZonesCompartmentsArenasCells, but does it for a
 * single zone.
 */
extern void
IterateZoneCompartmentsArenasCells(JSRuntime* rt, Zone* zone, void* data,
                                   IterateZoneCallback zoneCallback,
                                   JSIterateCompartmentCallback compartmentCallback,
                                   IterateArenaCallback arenaCallback,
                                   IterateCellCallback cellCallback);

/*
 * Invoke chunkCallback on every in-use chunk.
 */
extern void
IterateChunks(JSRuntime* rt, void* data, IterateChunkCallback chunkCallback);

typedef void (*IterateScriptCallback)(JSRuntime* rt, void* data, JSScript* script);

/*
 * Invoke scriptCallback on every in-use script for
 * the given compartment or for all compartments if it is null.
 */
extern void
IterateScripts(JSRuntime* rt, JSCompartment* compartment,
               void* data, IterateScriptCallback scriptCallback);

} /* namespace js */

extern void
js_FinalizeStringRT(JSRuntime* rt, JSString* str);

namespace js {

JSCompartment*
NewCompartment(JSContext* cx, JS::Zone* zone, JSPrincipals* principals,
               const JS::CompartmentOptions& options);

namespace gc {

extern void
GCIfNeeded(JSContext* cx);

/* Tries to run a GC no matter what (used for GC zeal). */
void
RunDebugGC(JSContext* cx);

void
SetDeterministicGC(JSContext* cx, bool enabled);

void
SetValidateGC(JSContext* cx, bool enabled);

void
SetFullCompartmentChecks(JSContext* cx, bool enabled);

/* Wait for the background thread to finish sweeping if it is running. */
void
FinishBackgroundFinalize(JSRuntime* rt);

/*
 * Merge all contents of source into target. This can only be used if source is
 * the only compartment in its zone.
 */
void
MergeCompartments(JSCompartment* source, JSCompartment* target);

const int ZealPokeValue = 1;
const int ZealAllocValue = 2;
const int ZealFrameGCValue = 3;
const int ZealVerifierPreValue = 4;
const int ZealFrameVerifierPreValue = 5;
const int ZealStackRootingValue = 6;
const int ZealGenerationalGCValue = 7;
const int ZealIncrementalRootsThenFinish = 8;
const int ZealIncrementalMarkAllThenFinish = 9;
const int ZealIncrementalMultipleSlices = 10;
const int ZealVerifierPostValue = 11;
const int ZealFrameVerifierPostValue = 12;
const int ZealCheckHashTablesOnMinorGC = 13;
const int ZealLimit = 13;

enum VerifierType {
    PreBarrierVerifier,
    PostBarrierVerifier
};

#ifdef JS_GC_ZEAL

/* Check that write barriers have been used correctly. See jsgc.cpp. */
void
VerifyBarriers(JSRuntime* rt, VerifierType type);

void
MaybeVerifyBarriers(JSContext* cx, bool always = false);

#else

static inline void
VerifyBarriers(JSRuntime* rt, VerifierType type)
{
}

static inline void
MaybeVerifyBarriers(JSContext* cx, bool always = false)
{
}

#endif

/*
 * Instances of this class set the |JSRuntime::suppressGC| flag for the duration
 * that they are live. Use of this class is highly discouraged. Please carefully
 * read the comment in vm/Runtime.h above |suppressGC| and take all appropriate
 * precautions before instantiating this class.
 */
class AutoSuppressGC
{
    int32_t& suppressGC_;

  public:
    AutoSuppressGC(ExclusiveContext* cx);
    AutoSuppressGC(JSCompartment* comp);
    AutoSuppressGC(JSRuntime* rt);

    ~AutoSuppressGC()
    {
        suppressGC_--;
    }
};

#ifdef DEBUG
/* Disable OOM testing in sections which are not OOM safe. */
class AutoEnterOOMUnsafeRegion
{
    uint32_t saved_;

  public:
    AutoEnterOOMUnsafeRegion() : saved_(OOM_maxAllocations) {
        OOM_maxAllocations = UINT32_MAX;
    }
    ~AutoEnterOOMUnsafeRegion() {
        OOM_maxAllocations = saved_;
    }
};
#else
class AutoEnterOOMUnsafeRegion {};
#endif /* DEBUG */

/* Prevent compartments and zones from being collected during iteration. */
class AutoEnterIteration {
    JSRuntime *rt;

  public:
    AutoEnterIteration(JSRuntime *rt_);
    ~AutoEnterIteration();
};

} /* namespace gc */

#ifdef DEBUG
/* Use this to avoid assertions when manipulating the wrapper map. */
class AutoDisableProxyCheck
{
    MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER;
    uintptr_t& count;

  public:
    AutoDisableProxyCheck(JSRuntime* rt
                          MOZ_GUARD_OBJECT_NOTIFIER_PARAM);

    ~AutoDisableProxyCheck() {
        count--;
    }
};
#else
struct AutoDisableProxyCheck
{
    AutoDisableProxyCheck(JSRuntime* rt) {}
};
#endif

void
PurgeJITCaches(JS::Zone* zone);

// This is the same as IsInsideNursery, but not inlined.
bool
UninlinedIsInsideNursery(JSRuntime* rt, const void* thing);

} /* namespace js */

#endif /* jsgc_h */