diff -r 000000000000 -r 6474c204b198 js/src/gc/Heap.h --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/js/src/gc/Heap.h Wed Dec 31 06:09:35 2014 +0100 @@ -0,0 +1,1148 @@ +/* -*- 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/. */ + +#ifndef gc_Heap_h +#define gc_Heap_h + +#include "mozilla/Attributes.h" +#include "mozilla/PodOperations.h" + +#include +#include + +#include "jspubtd.h" +#include "jstypes.h" +#include "jsutil.h" + +#include "ds/BitArray.h" +#include "gc/Memory.h" +#include "js/HeapAPI.h" + +struct JSCompartment; + +struct JSRuntime; + +namespace JS { +namespace shadow { +class Runtime; +} +} + +namespace js { + +class FreeOp; + +namespace gc { + +struct Arena; +struct ArenaList; +struct ArenaHeader; +struct Chunk; + +/* + * This flag allows an allocation site to request a specific heap based upon the + * estimated lifetime or lifetime requirements of objects allocated from that + * site. + */ +enum InitialHeap { + DefaultHeap, + TenuredHeap +}; + +/* The GC allocation kinds. */ +enum AllocKind { + FINALIZE_OBJECT0, + FINALIZE_OBJECT0_BACKGROUND, + FINALIZE_OBJECT2, + FINALIZE_OBJECT2_BACKGROUND, + FINALIZE_OBJECT4, + FINALIZE_OBJECT4_BACKGROUND, + FINALIZE_OBJECT8, + FINALIZE_OBJECT8_BACKGROUND, + FINALIZE_OBJECT12, + FINALIZE_OBJECT12_BACKGROUND, + FINALIZE_OBJECT16, + FINALIZE_OBJECT16_BACKGROUND, + FINALIZE_OBJECT_LAST = FINALIZE_OBJECT16_BACKGROUND, + FINALIZE_SCRIPT, + FINALIZE_LAZY_SCRIPT, + FINALIZE_SHAPE, + FINALIZE_BASE_SHAPE, + FINALIZE_TYPE_OBJECT, + FINALIZE_FAT_INLINE_STRING, + FINALIZE_STRING, + FINALIZE_EXTERNAL_STRING, + FINALIZE_JITCODE, + FINALIZE_LAST = FINALIZE_JITCODE +}; + +static const unsigned FINALIZE_LIMIT = FINALIZE_LAST + 1; +static const unsigned FINALIZE_OBJECT_LIMIT = FINALIZE_OBJECT_LAST + 1; + +/* + * This must be an upper bound, but we do not need the least upper bound, so + * we just exclude non-background objects. + */ +static const size_t MAX_BACKGROUND_FINALIZE_KINDS = FINALIZE_LIMIT - FINALIZE_OBJECT_LIMIT / 2; + +/* + * A GC cell is the base class for all GC things. + */ +struct Cell +{ + public: + inline ArenaHeader *arenaHeader() const; + inline AllocKind tenuredGetAllocKind() const; + MOZ_ALWAYS_INLINE bool isMarked(uint32_t color = BLACK) const; + MOZ_ALWAYS_INLINE bool markIfUnmarked(uint32_t color = BLACK) const; + MOZ_ALWAYS_INLINE void unmark(uint32_t color) const; + + inline JSRuntime *runtimeFromMainThread() const; + inline JS::shadow::Runtime *shadowRuntimeFromMainThread() const; + inline JS::Zone *tenuredZone() const; + inline JS::Zone *tenuredZoneFromAnyThread() const; + inline bool tenuredIsInsideZone(JS::Zone *zone) const; + + // Note: Unrestricted access to the runtime of a GC thing from an arbitrary + // thread can easily lead to races. Use this method very carefully. + inline JSRuntime *runtimeFromAnyThread() const; + inline JS::shadow::Runtime *shadowRuntimeFromAnyThread() const; + +#ifdef DEBUG + inline bool isAligned() const; + inline bool isTenured() const; +#endif + + protected: + inline uintptr_t address() const; + inline Chunk *chunk() const; +}; + +/* + * The mark bitmap has one bit per each GC cell. For multi-cell GC things this + * wastes space but allows to avoid expensive devisions by thing's size when + * accessing the bitmap. In addition this allows to use some bits for colored + * marking during the cycle GC. + */ +const size_t ArenaCellCount = size_t(1) << (ArenaShift - CellShift); +const size_t ArenaBitmapBits = ArenaCellCount; +const size_t ArenaBitmapBytes = ArenaBitmapBits / 8; +const size_t ArenaBitmapWords = ArenaBitmapBits / JS_BITS_PER_WORD; + +/* + * A FreeSpan represents a contiguous sequence of free cells in an Arena. + * |first| is the address of the first free cell in the span. |last| is the + * address of the last free cell in the span. This last cell holds a FreeSpan + * data structure for the next span unless this is the last span on the list + * of spans in the arena. For this last span |last| points to the last byte of + * the last thing in the arena and no linkage is stored there, so + * |last| == arenaStart + ArenaSize - 1. If the space at the arena end is + * fully used this last span is empty and |first| == |last + 1|. + * + * Thus |first| < |last| implies that we have either the last span with at least + * one element or that the span is not the last and contains at least 2 + * elements. In both cases to allocate a thing from this span we need simply + * to increment |first| by the allocation size. + * + * |first| == |last| implies that we have a one element span that records the + * next span. So to allocate from it we need to update the span list head + * with a copy of the span stored at |last| address so the following + * allocations will use that span. + * + * |first| > |last| implies that we have an empty last span and the arena is + * fully used. + * + * Also only for the last span (|last| & 1)! = 0 as all allocation sizes are + * multiples of CellSize. + */ +struct FreeSpan +{ + uintptr_t first; + uintptr_t last; + + public: + FreeSpan() {} + + FreeSpan(uintptr_t first, uintptr_t last) + : first(first), last(last) { + checkSpan(); + } + + /* + * To minimize the size of the arena header the first span is encoded + * there as offsets from the arena start. + */ + static size_t encodeOffsets(size_t firstOffset, size_t lastOffset) { + static_assert(ArenaShift < 16, "Check that we can pack offsets into uint16_t."); + JS_ASSERT(firstOffset <= ArenaSize); + JS_ASSERT(lastOffset < ArenaSize); + JS_ASSERT(firstOffset <= ((lastOffset + 1) & ~size_t(1))); + return firstOffset | (lastOffset << 16); + } + + /* + * Encoded offsets for a full arena when its first span is the last one + * and empty. + */ + static const size_t FullArenaOffsets = ArenaSize | ((ArenaSize - 1) << 16); + + static FreeSpan decodeOffsets(uintptr_t arenaAddr, size_t offsets) { + JS_ASSERT(!(arenaAddr & ArenaMask)); + + size_t firstOffset = offsets & 0xFFFF; + size_t lastOffset = offsets >> 16; + JS_ASSERT(firstOffset <= ArenaSize); + JS_ASSERT(lastOffset < ArenaSize); + + /* + * We must not use | when calculating first as firstOffset is + * ArenaMask + 1 for the empty span. + */ + return FreeSpan(arenaAddr + firstOffset, arenaAddr | lastOffset); + } + + void initAsEmpty(uintptr_t arenaAddr = 0) { + JS_ASSERT(!(arenaAddr & ArenaMask)); + first = arenaAddr + ArenaSize; + last = arenaAddr | (ArenaSize - 1); + JS_ASSERT(isEmpty()); + } + + bool isEmpty() const { + checkSpan(); + return first > last; + } + + bool hasNext() const { + checkSpan(); + return !(last & uintptr_t(1)); + } + + const FreeSpan *nextSpan() const { + JS_ASSERT(hasNext()); + return reinterpret_cast(last); + } + + FreeSpan *nextSpanUnchecked(size_t thingSize) const { +#ifdef DEBUG + uintptr_t lastOffset = last & ArenaMask; + JS_ASSERT(!(lastOffset & 1)); + JS_ASSERT((ArenaSize - lastOffset) % thingSize == 0); +#endif + return reinterpret_cast(last); + } + + uintptr_t arenaAddressUnchecked() const { + return last & ~ArenaMask; + } + + uintptr_t arenaAddress() const { + checkSpan(); + return arenaAddressUnchecked(); + } + + ArenaHeader *arenaHeader() const { + return reinterpret_cast(arenaAddress()); + } + + bool isSameNonEmptySpan(const FreeSpan *another) const { + JS_ASSERT(!isEmpty()); + JS_ASSERT(!another->isEmpty()); + return first == another->first && last == another->last; + } + + bool isWithinArena(uintptr_t arenaAddr) const { + JS_ASSERT(!(arenaAddr & ArenaMask)); + + /* Return true for the last empty span as well. */ + return arenaAddress() == arenaAddr; + } + + size_t encodeAsOffsets() const { + /* + * We must use first - arenaAddress(), not first & ArenaMask as + * first == ArenaMask + 1 for an empty span. + */ + uintptr_t arenaAddr = arenaAddress(); + return encodeOffsets(first - arenaAddr, last & ArenaMask); + } + + /* See comments before FreeSpan for details. */ + MOZ_ALWAYS_INLINE void *allocate(size_t thingSize) { + JS_ASSERT(thingSize % CellSize == 0); + checkSpan(); + uintptr_t thing = first; + if (thing < last) { + /* Bump-allocate from the current span. */ + first = thing + thingSize; + } else if (MOZ_LIKELY(thing == last)) { + /* + * Move to the next span. We use MOZ_LIKELY as without PGO + * compilers mis-predict == here as unlikely to succeed. + */ + *this = *reinterpret_cast(thing); + } else { + return nullptr; + } + checkSpan(); + JS_EXTRA_POISON(reinterpret_cast(thing), JS_ALLOCATED_TENURED_PATTERN, thingSize); + return reinterpret_cast(thing); + } + + /* A version of allocate when we know that the span is not empty. */ + MOZ_ALWAYS_INLINE void *infallibleAllocate(size_t thingSize) { + JS_ASSERT(thingSize % CellSize == 0); + checkSpan(); + uintptr_t thing = first; + if (thing < last) { + first = thing + thingSize; + } else { + JS_ASSERT(thing == last); + *this = *reinterpret_cast(thing); + } + checkSpan(); + JS_EXTRA_POISON(reinterpret_cast(thing), JS_ALLOCATED_TENURED_PATTERN, thingSize); + return reinterpret_cast(thing); + } + + /* + * Allocate from a newly allocated arena. We do not move the free list + * from the arena. Rather we set the arena up as fully used during the + * initialization so to allocate we simply return the first thing in the + * arena and set the free list to point to the second. + */ + MOZ_ALWAYS_INLINE void *allocateFromNewArena(uintptr_t arenaAddr, size_t firstThingOffset, + size_t thingSize) { + JS_ASSERT(!(arenaAddr & ArenaMask)); + uintptr_t thing = arenaAddr | firstThingOffset; + first = thing + thingSize; + last = arenaAddr | ArenaMask; + checkSpan(); + JS_EXTRA_POISON(reinterpret_cast(thing), JS_ALLOCATED_TENURED_PATTERN, thingSize); + return reinterpret_cast(thing); + } + + void checkSpan() const { +#ifdef DEBUG + /* We do not allow spans at the end of the address space. */ + JS_ASSERT(last != uintptr_t(-1)); + JS_ASSERT(first); + JS_ASSERT(last); + JS_ASSERT(first - 1 <= last); + uintptr_t arenaAddr = arenaAddressUnchecked(); + if (last & 1) { + /* The span is the last. */ + JS_ASSERT((last & ArenaMask) == ArenaMask); + + if (first - 1 == last) { + /* The span is last and empty. The above start != 0 check + * implies that we are not at the end of the address space. + */ + return; + } + size_t spanLength = last - first + 1; + JS_ASSERT(spanLength % CellSize == 0); + + /* Start and end must belong to the same arena. */ + JS_ASSERT((first & ~ArenaMask) == arenaAddr); + return; + } + + /* The span is not the last and we have more spans to follow. */ + JS_ASSERT(first <= last); + size_t spanLengthWithoutOneThing = last - first; + JS_ASSERT(spanLengthWithoutOneThing % CellSize == 0); + + JS_ASSERT((first & ~ArenaMask) == arenaAddr); + + /* + * If there is not enough space before the arena end to allocate one + * more thing, then the span must be marked as the last one to avoid + * storing useless empty span reference. + */ + size_t beforeTail = ArenaSize - (last & ArenaMask); + JS_ASSERT(beforeTail >= sizeof(FreeSpan) + CellSize); + + FreeSpan *next = reinterpret_cast(last); + + /* + * The GC things on the list of free spans come from one arena + * and the spans are linked in ascending address order with + * at least one non-free thing between spans. + */ + JS_ASSERT(last < next->first); + JS_ASSERT(arenaAddr == next->arenaAddressUnchecked()); + + if (next->first > next->last) { + /* + * The next span is the empty span that terminates the list for + * arenas that do not have any free things at the end. + */ + JS_ASSERT(next->first - 1 == next->last); + JS_ASSERT(arenaAddr + ArenaSize == next->first); + } +#endif + } + +}; + +/* Every arena has a header. */ +struct ArenaHeader : public JS::shadow::ArenaHeader +{ + friend struct FreeLists; + + /* + * ArenaHeader::next has two purposes: when unallocated, it points to the + * next available Arena's header. When allocated, it points to the next + * arena of the same size class and compartment. + */ + ArenaHeader *next; + + private: + /* + * The first span of free things in the arena. We encode it as the start + * and end offsets within the arena, not as FreeSpan structure, to + * minimize the header size. + */ + size_t firstFreeSpanOffsets; + + /* + * One of AllocKind constants or FINALIZE_LIMIT when the arena does not + * contain any GC things and is on the list of empty arenas in the GC + * chunk. The latter allows to quickly check if the arena is allocated + * during the conservative GC scanning without searching the arena in the + * list. + * + * We use 8 bits for the allocKind so the compiler can use byte-level memory + * instructions to access it. + */ + size_t allocKind : 8; + + /* + * When collecting we sometimes need to keep an auxillary list of arenas, + * for which we use the following fields. This happens for several reasons: + * + * When recursive marking uses too much stack the marking is delayed and the + * corresponding arenas are put into a stack. To distinguish the bottom of + * the stack from the arenas not present in the stack we use the + * markOverflow flag to tag arenas on the stack. + * + * Delayed marking is also used for arenas that we allocate into during an + * incremental GC. In this case, we intend to mark all the objects in the + * arena, and it's faster to do this marking in bulk. + * + * When sweeping we keep track of which arenas have been allocated since the + * end of the mark phase. This allows us to tell whether a pointer to an + * unmarked object is yet to be finalized or has already been reallocated. + * We set the allocatedDuringIncremental flag for this and clear it at the + * end of the sweep phase. + * + * To minimize the ArenaHeader size we record the next linkage as + * arenaAddress() >> ArenaShift and pack it with the allocKind field and the + * flags. + */ + public: + size_t hasDelayedMarking : 1; + size_t allocatedDuringIncremental : 1; + size_t markOverflow : 1; + size_t auxNextLink : JS_BITS_PER_WORD - 8 - 1 - 1 - 1; + static_assert(ArenaShift >= 8 + 1 + 1 + 1, + "ArenaHeader::auxNextLink packing assumes that ArenaShift has enough bits to " + "cover allocKind and hasDelayedMarking."); + + inline uintptr_t address() const; + inline Chunk *chunk() const; + + bool allocated() const { + JS_ASSERT(allocKind <= size_t(FINALIZE_LIMIT)); + return allocKind < size_t(FINALIZE_LIMIT); + } + + void init(JS::Zone *zoneArg, AllocKind kind) { + JS_ASSERT(!allocated()); + JS_ASSERT(!markOverflow); + JS_ASSERT(!allocatedDuringIncremental); + JS_ASSERT(!hasDelayedMarking); + zone = zoneArg; + + static_assert(FINALIZE_LIMIT <= 255, "We must be able to fit the allockind into uint8_t."); + allocKind = size_t(kind); + + /* See comments in FreeSpan::allocateFromNewArena. */ + firstFreeSpanOffsets = FreeSpan::FullArenaOffsets; + } + + void setAsNotAllocated() { + allocKind = size_t(FINALIZE_LIMIT); + markOverflow = 0; + allocatedDuringIncremental = 0; + hasDelayedMarking = 0; + auxNextLink = 0; + } + + inline uintptr_t arenaAddress() const; + inline Arena *getArena(); + + AllocKind getAllocKind() const { + JS_ASSERT(allocated()); + return AllocKind(allocKind); + } + + inline size_t getThingSize() const; + + bool hasFreeThings() const { + return firstFreeSpanOffsets != FreeSpan::FullArenaOffsets; + } + + inline bool isEmpty() const; + + void setAsFullyUsed() { + firstFreeSpanOffsets = FreeSpan::FullArenaOffsets; + } + + inline FreeSpan getFirstFreeSpan() const; + inline void setFirstFreeSpan(const FreeSpan *span); + +#ifdef DEBUG + void checkSynchronizedWithFreeList() const; +#endif + + inline ArenaHeader *getNextDelayedMarking() const; + inline void setNextDelayedMarking(ArenaHeader *aheader); + inline void unsetDelayedMarking(); + + inline ArenaHeader *getNextAllocDuringSweep() const; + inline void setNextAllocDuringSweep(ArenaHeader *aheader); + inline void unsetAllocDuringSweep(); +}; + +struct Arena +{ + /* + * Layout of an arena: + * An arena is 4K in size and 4K-aligned. It starts with the ArenaHeader + * descriptor followed by some pad bytes. The remainder of the arena is + * filled with the array of T things. The pad bytes ensure that the thing + * array ends exactly at the end of the arena. + * + * +-------------+-----+----+----+-----+----+ + * | ArenaHeader | pad | T0 | T1 | ... | Tn | + * +-------------+-----+----+----+-----+----+ + * + * <----------------------------------------> = ArenaSize bytes + * <-------------------> = first thing offset + */ + ArenaHeader aheader; + uint8_t data[ArenaSize - sizeof(ArenaHeader)]; + + private: + static JS_FRIEND_DATA(const uint32_t) ThingSizes[]; + static JS_FRIEND_DATA(const uint32_t) FirstThingOffsets[]; + + public: + static void staticAsserts(); + + static size_t thingSize(AllocKind kind) { + return ThingSizes[kind]; + } + + static size_t firstThingOffset(AllocKind kind) { + return FirstThingOffsets[kind]; + } + + static size_t thingsPerArena(size_t thingSize) { + JS_ASSERT(thingSize % CellSize == 0); + + /* We should be able to fit FreeSpan in any GC thing. */ + JS_ASSERT(thingSize >= sizeof(FreeSpan)); + + return (ArenaSize - sizeof(ArenaHeader)) / thingSize; + } + + static size_t thingsSpan(size_t thingSize) { + return thingsPerArena(thingSize) * thingSize; + } + + static bool isAligned(uintptr_t thing, size_t thingSize) { + /* Things ends at the arena end. */ + uintptr_t tailOffset = (ArenaSize - thing) & ArenaMask; + return tailOffset % thingSize == 0; + } + + uintptr_t address() const { + return aheader.address(); + } + + uintptr_t thingsStart(AllocKind thingKind) { + return address() | firstThingOffset(thingKind); + } + + uintptr_t thingsEnd() { + return address() + ArenaSize; + } + + void setAsFullyUnused(AllocKind thingKind); + + template + bool finalize(FreeOp *fop, AllocKind thingKind, size_t thingSize); +}; + +static_assert(sizeof(Arena) == ArenaSize, "The hardcoded arena size must match the struct size."); + +inline size_t +ArenaHeader::getThingSize() const +{ + JS_ASSERT(allocated()); + return Arena::thingSize(getAllocKind()); +} + +/* + * The tail of the chunk info is shared between all chunks in the system, both + * nursery and tenured. This structure is locatable from any GC pointer by + * aligning to 1MiB. + */ +struct ChunkTrailer +{ + /* The index the chunk in the nursery, or LocationTenuredHeap. */ + uint32_t location; + +#if JS_BITS_PER_WORD == 64 + uint32_t padding; +#endif + + JSRuntime *runtime; +}; + +static_assert(sizeof(ChunkTrailer) == 2 * sizeof(uintptr_t), "ChunkTrailer size is incorrect."); + +/* The chunk header (located at the end of the chunk to preserve arena alignment). */ +struct ChunkInfo +{ + Chunk *next; + Chunk **prevp; + + /* Free arenas are linked together with aheader.next. */ + ArenaHeader *freeArenasHead; + +#if JS_BITS_PER_WORD == 32 + /* + * Calculating sizes and offsets is simpler if sizeof(ChunkInfo) is + * architecture-independent. + */ + char padding[20]; +#endif + + /* + * Decommitted arenas are tracked by a bitmap in the chunk header. We use + * this offset to start our search iteration close to a decommitted arena + * that we can allocate. + */ + uint32_t lastDecommittedArenaOffset; + + /* Number of free arenas, either committed or decommitted. */ + uint32_t numArenasFree; + + /* Number of free, committed arenas. */ + uint32_t numArenasFreeCommitted; + + /* Number of GC cycles this chunk has survived. */ + uint32_t age; + + /* Information shared by all Chunk types. */ + ChunkTrailer trailer; +}; + +/* + * Calculating ArenasPerChunk: + * + * In order to figure out how many Arenas will fit in a chunk, we need to know + * how much extra space is available after we allocate the header data. This + * is a problem because the header size depends on the number of arenas in the + * chunk. The two dependent fields are bitmap and decommittedArenas. + * + * For the mark bitmap, we know that each arena will use a fixed number of full + * bytes: ArenaBitmapBytes. The full size of the header data is this number + * multiplied by the eventual number of arenas we have in the header. We, + * conceptually, distribute this header data among the individual arenas and do + * not include it in the header. This way we do not have to worry about its + * variable size: it gets attached to the variable number we are computing. + * + * For the decommitted arena bitmap, we only have 1 bit per arena, so this + * technique will not work. Instead, we observe that we do not have enough + * header info to fill 8 full arenas: it is currently 4 on 64bit, less on + * 32bit. Thus, with current numbers, we need 64 bytes for decommittedArenas. + * This will not become 63 bytes unless we double the data required in the + * header. Therefore, we just compute the number of bytes required to track + * every possible arena and do not worry about slop bits, since there are too + * few to usefully allocate. + * + * To actually compute the number of arenas we can allocate in a chunk, we + * divide the amount of available space less the header info (not including + * the mark bitmap which is distributed into the arena size) by the size of + * the arena (with the mark bitmap bytes it uses). + */ +const size_t BytesPerArenaWithHeader = ArenaSize + ArenaBitmapBytes; +const size_t ChunkDecommitBitmapBytes = ChunkSize / ArenaSize / JS_BITS_PER_BYTE; +const size_t ChunkBytesAvailable = ChunkSize - sizeof(ChunkInfo) - ChunkDecommitBitmapBytes; +const size_t ArenasPerChunk = ChunkBytesAvailable / BytesPerArenaWithHeader; +static_assert(ArenasPerChunk == 252, "Do not accidentally change our heap's density."); + +/* A chunk bitmap contains enough mark bits for all the cells in a chunk. */ +struct ChunkBitmap +{ + volatile uintptr_t bitmap[ArenaBitmapWords * ArenasPerChunk]; + + public: + ChunkBitmap() { } + + MOZ_ALWAYS_INLINE void getMarkWordAndMask(const Cell *cell, uint32_t color, + uintptr_t **wordp, uintptr_t *maskp) + { + GetGCThingMarkWordAndMask(cell, color, wordp, maskp); + } + + MOZ_ALWAYS_INLINE MOZ_TSAN_BLACKLIST bool isMarked(const Cell *cell, uint32_t color) { + uintptr_t *word, mask; + getMarkWordAndMask(cell, color, &word, &mask); + return *word & mask; + } + + MOZ_ALWAYS_INLINE bool markIfUnmarked(const Cell *cell, uint32_t color) { + uintptr_t *word, mask; + getMarkWordAndMask(cell, BLACK, &word, &mask); + if (*word & mask) + return false; + *word |= mask; + if (color != BLACK) { + /* + * We use getMarkWordAndMask to recalculate both mask and word as + * doing just mask << color may overflow the mask. + */ + getMarkWordAndMask(cell, color, &word, &mask); + if (*word & mask) + return false; + *word |= mask; + } + return true; + } + + MOZ_ALWAYS_INLINE void unmark(const Cell *cell, uint32_t color) { + uintptr_t *word, mask; + getMarkWordAndMask(cell, color, &word, &mask); + *word &= ~mask; + } + + void clear() { + memset((void *)bitmap, 0, sizeof(bitmap)); + } + + uintptr_t *arenaBits(ArenaHeader *aheader) { + static_assert(ArenaBitmapBits == ArenaBitmapWords * JS_BITS_PER_WORD, + "We assume that the part of the bitmap corresponding to the arena " + "has the exact number of words so we do not need to deal with a word " + "that covers bits from two arenas."); + + uintptr_t *word, unused; + getMarkWordAndMask(reinterpret_cast(aheader->address()), BLACK, &word, &unused); + return word; + } +}; + +static_assert(ArenaBitmapBytes * ArenasPerChunk == sizeof(ChunkBitmap), + "Ensure our ChunkBitmap actually covers all arenas."); +static_assert(js::gc::ChunkMarkBitmapBits == ArenaBitmapBits * ArenasPerChunk, + "Ensure that the mark bitmap has the right number of bits."); + +typedef BitArray PerArenaBitmap; + +const size_t ChunkPadSize = ChunkSize + - (sizeof(Arena) * ArenasPerChunk) + - sizeof(ChunkBitmap) + - sizeof(PerArenaBitmap) + - sizeof(ChunkInfo); +static_assert(ChunkPadSize < BytesPerArenaWithHeader, + "If the chunk padding is larger than an arena, we should have one more arena."); + +/* + * Chunks contain arenas and associated data structures (mark bitmap, delayed + * marking state). + */ +struct Chunk +{ + Arena arenas[ArenasPerChunk]; + + /* Pad to full size to ensure cache alignment of ChunkInfo. */ + uint8_t padding[ChunkPadSize]; + + ChunkBitmap bitmap; + PerArenaBitmap decommittedArenas; + ChunkInfo info; + + static Chunk *fromAddress(uintptr_t addr) { + addr &= ~ChunkMask; + return reinterpret_cast(addr); + } + + static bool withinArenasRange(uintptr_t addr) { + uintptr_t offset = addr & ChunkMask; + return offset < ArenasPerChunk * ArenaSize; + } + + static size_t arenaIndex(uintptr_t addr) { + JS_ASSERT(withinArenasRange(addr)); + return (addr & ChunkMask) >> ArenaShift; + } + + uintptr_t address() const { + uintptr_t addr = reinterpret_cast(this); + JS_ASSERT(!(addr & ChunkMask)); + return addr; + } + + bool unused() const { + return info.numArenasFree == ArenasPerChunk; + } + + bool hasAvailableArenas() const { + return info.numArenasFree != 0; + } + + inline void addToAvailableList(JS::Zone *zone); + inline void insertToAvailableList(Chunk **insertPoint); + inline void removeFromAvailableList(); + + ArenaHeader *allocateArena(JS::Zone *zone, AllocKind kind); + + void releaseArena(ArenaHeader *aheader); + void recycleArena(ArenaHeader *aheader, ArenaList &dest, AllocKind thingKind); + + static Chunk *allocate(JSRuntime *rt); + + void decommitAllArenas(JSRuntime *rt) { + decommittedArenas.clear(true); + MarkPagesUnused(rt, &arenas[0], ArenasPerChunk * ArenaSize); + + info.freeArenasHead = nullptr; + info.lastDecommittedArenaOffset = 0; + info.numArenasFree = ArenasPerChunk; + info.numArenasFreeCommitted = 0; + } + + /* Must be called with the GC lock taken. */ + static inline void release(JSRuntime *rt, Chunk *chunk); + static inline void releaseList(JSRuntime *rt, Chunk *chunkListHead); + + /* Must be called with the GC lock taken. */ + inline void prepareToBeFreed(JSRuntime *rt); + + /* + * Assuming that the info.prevp points to the next field of the previous + * chunk in a doubly-linked list, get that chunk. + */ + Chunk *getPrevious() { + JS_ASSERT(info.prevp); + return fromPointerToNext(info.prevp); + } + + /* Get the chunk from a pointer to its info.next field. */ + static Chunk *fromPointerToNext(Chunk **nextFieldPtr) { + uintptr_t addr = reinterpret_cast(nextFieldPtr); + JS_ASSERT((addr & ChunkMask) == offsetof(Chunk, info.next)); + return reinterpret_cast(addr - offsetof(Chunk, info.next)); + } + + private: + inline void init(JSRuntime *rt); + + /* Search for a decommitted arena to allocate. */ + unsigned findDecommittedArenaOffset(); + ArenaHeader* fetchNextDecommittedArena(); + + public: + /* Unlink and return the freeArenasHead. */ + inline ArenaHeader* fetchNextFreeArena(JSRuntime *rt); + + inline void addArenaToFreeList(JSRuntime *rt, ArenaHeader *aheader); +}; + +static_assert(sizeof(Chunk) == ChunkSize, + "Ensure the hardcoded chunk size definition actually matches the struct."); +static_assert(js::gc::ChunkMarkBitmapOffset == offsetof(Chunk, bitmap), + "The hardcoded API bitmap offset must match the actual offset."); +static_assert(js::gc::ChunkRuntimeOffset == offsetof(Chunk, info) + + offsetof(ChunkInfo, trailer) + + offsetof(ChunkTrailer, runtime), + "The hardcoded API runtime offset must match the actual offset."); + +inline uintptr_t +ArenaHeader::address() const +{ + uintptr_t addr = reinterpret_cast(this); + JS_ASSERT(!(addr & ArenaMask)); + JS_ASSERT(Chunk::withinArenasRange(addr)); + return addr; +} + +inline Chunk * +ArenaHeader::chunk() const +{ + return Chunk::fromAddress(address()); +} + +inline uintptr_t +ArenaHeader::arenaAddress() const +{ + return address(); +} + +inline Arena * +ArenaHeader::getArena() +{ + return reinterpret_cast(arenaAddress()); +} + +inline bool +ArenaHeader::isEmpty() const +{ + /* Arena is empty if its first span covers the whole arena. */ + JS_ASSERT(allocated()); + size_t firstThingOffset = Arena::firstThingOffset(getAllocKind()); + return firstFreeSpanOffsets == FreeSpan::encodeOffsets(firstThingOffset, ArenaMask); +} + +FreeSpan +ArenaHeader::getFirstFreeSpan() const +{ +#ifdef DEBUG + checkSynchronizedWithFreeList(); +#endif + return FreeSpan::decodeOffsets(arenaAddress(), firstFreeSpanOffsets); +} + +void +ArenaHeader::setFirstFreeSpan(const FreeSpan *span) +{ + JS_ASSERT(span->isWithinArena(arenaAddress())); + firstFreeSpanOffsets = span->encodeAsOffsets(); +} + +inline ArenaHeader * +ArenaHeader::getNextDelayedMarking() const +{ + JS_ASSERT(hasDelayedMarking); + return &reinterpret_cast(auxNextLink << ArenaShift)->aheader; +} + +inline void +ArenaHeader::setNextDelayedMarking(ArenaHeader *aheader) +{ + JS_ASSERT(!(uintptr_t(aheader) & ArenaMask)); + JS_ASSERT(!auxNextLink && !hasDelayedMarking); + hasDelayedMarking = 1; + auxNextLink = aheader->arenaAddress() >> ArenaShift; +} + +inline void +ArenaHeader::unsetDelayedMarking() +{ + JS_ASSERT(hasDelayedMarking); + hasDelayedMarking = 0; + auxNextLink = 0; +} + +inline ArenaHeader * +ArenaHeader::getNextAllocDuringSweep() const +{ + JS_ASSERT(allocatedDuringIncremental); + return &reinterpret_cast(auxNextLink << ArenaShift)->aheader; +} + +inline void +ArenaHeader::setNextAllocDuringSweep(ArenaHeader *aheader) +{ + JS_ASSERT(!auxNextLink && !allocatedDuringIncremental); + allocatedDuringIncremental = 1; + auxNextLink = aheader->arenaAddress() >> ArenaShift; +} + +inline void +ArenaHeader::unsetAllocDuringSweep() +{ + JS_ASSERT(allocatedDuringIncremental); + allocatedDuringIncremental = 0; + auxNextLink = 0; +} + +static void +AssertValidColor(const void *thing, uint32_t color) +{ +#ifdef DEBUG + ArenaHeader *aheader = reinterpret_cast(thing)->arenaHeader(); + JS_ASSERT(color < aheader->getThingSize() / CellSize); +#endif +} + +inline ArenaHeader * +Cell::arenaHeader() const +{ + JS_ASSERT(isTenured()); + uintptr_t addr = address(); + addr &= ~ArenaMask; + return reinterpret_cast(addr); +} + +inline JSRuntime * +Cell::runtimeFromMainThread() const +{ + JSRuntime *rt = chunk()->info.trailer.runtime; + JS_ASSERT(CurrentThreadCanAccessRuntime(rt)); + return rt; +} + +inline JS::shadow::Runtime * +Cell::shadowRuntimeFromMainThread() const +{ + return reinterpret_cast(runtimeFromMainThread()); +} + +inline JSRuntime * +Cell::runtimeFromAnyThread() const +{ + return chunk()->info.trailer.runtime; +} + +inline JS::shadow::Runtime * +Cell::shadowRuntimeFromAnyThread() const +{ + return reinterpret_cast(runtimeFromAnyThread()); +} + +bool +Cell::isMarked(uint32_t color /* = BLACK */) const +{ + JS_ASSERT(isTenured()); + JS_ASSERT(arenaHeader()->allocated()); + AssertValidColor(this, color); + return chunk()->bitmap.isMarked(this, color); +} + +bool +Cell::markIfUnmarked(uint32_t color /* = BLACK */) const +{ + JS_ASSERT(isTenured()); + AssertValidColor(this, color); + return chunk()->bitmap.markIfUnmarked(this, color); +} + +void +Cell::unmark(uint32_t color) const +{ + JS_ASSERT(isTenured()); + JS_ASSERT(color != BLACK); + AssertValidColor(this, color); + chunk()->bitmap.unmark(this, color); +} + +JS::Zone * +Cell::tenuredZone() const +{ + JS::Zone *zone = arenaHeader()->zone; + JS_ASSERT(CurrentThreadCanAccessZone(zone)); + JS_ASSERT(isTenured()); + return zone; +} + +JS::Zone * +Cell::tenuredZoneFromAnyThread() const +{ + JS_ASSERT(isTenured()); + return arenaHeader()->zone; +} + +bool +Cell::tenuredIsInsideZone(JS::Zone *zone) const +{ + JS_ASSERT(isTenured()); + return zone == arenaHeader()->zone; +} + +#ifdef DEBUG +bool +Cell::isAligned() const +{ + return Arena::isAligned(address(), arenaHeader()->getThingSize()); +} + +bool +Cell::isTenured() const +{ +#ifdef JSGC_GENERATIONAL + JS::shadow::Runtime *rt = js::gc::GetGCThingRuntime(this); + return !IsInsideNursery(rt, this); +#endif + return true; +} +#endif + +inline uintptr_t +Cell::address() const +{ + uintptr_t addr = uintptr_t(this); + JS_ASSERT(addr % CellSize == 0); + JS_ASSERT(Chunk::withinArenasRange(addr)); + return addr; +} + +Chunk * +Cell::chunk() const +{ + uintptr_t addr = uintptr_t(this); + JS_ASSERT(addr % CellSize == 0); + addr &= ~(ChunkSize - 1); + return reinterpret_cast(addr); +} + +inline bool +InFreeList(ArenaHeader *aheader, void *thing) +{ + if (!aheader->hasFreeThings()) + return false; + + FreeSpan firstSpan(aheader->getFirstFreeSpan()); + uintptr_t addr = reinterpret_cast(thing); + + for (const FreeSpan *span = &firstSpan;;) { + /* If the thing comes before the current span, it's not free. */ + if (addr < span->first) + return false; + + /* + * If we find it inside the span, it's dead. We use here "<=" and not + * "<" even for the last span as we know that thing is inside the + * arena. Thus, for the last span thing < span->end. + */ + if (addr <= span->last) + return true; + + /* + * The last possible empty span is an the end of the arena. Here + * span->end < thing < thingsEnd and so we must have more spans. + */ + span = span->nextSpan(); + } +} + +} /* namespace gc */ + +gc::AllocKind +gc::Cell::tenuredGetAllocKind() const +{ + return arenaHeader()->getAllocKind(); +} + +} /* namespace js */ + +#endif /* gc_Heap_h */