1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/js/public/HeapAPI.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,243 @@
1.4 +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
1.5 + * vim: set ts=8 sts=4 et sw=4 tw=99:
1.6 + * This Source Code Form is subject to the terms of the Mozilla Public
1.7 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.8 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.9 +
1.10 +#ifndef js_HeapAPI_h
1.11 +#define js_HeapAPI_h
1.12 +
1.13 +#include <limits.h>
1.14 +
1.15 +#include "jspubtd.h"
1.16 +
1.17 +#include "js/Utility.h"
1.18 +
1.19 +/* These values are private to the JS engine. */
1.20 +namespace js {
1.21 +
1.22 +// Whether the current thread is permitted access to any part of the specified
1.23 +// runtime or zone.
1.24 +JS_FRIEND_API(bool)
1.25 +CurrentThreadCanAccessRuntime(JSRuntime *rt);
1.26 +
1.27 +JS_FRIEND_API(bool)
1.28 +CurrentThreadCanAccessZone(JS::Zone *zone);
1.29 +
1.30 +namespace gc {
1.31 +
1.32 +struct Cell;
1.33 +
1.34 +const size_t ArenaShift = 12;
1.35 +const size_t ArenaSize = size_t(1) << ArenaShift;
1.36 +const size_t ArenaMask = ArenaSize - 1;
1.37 +
1.38 +const size_t ChunkShift = 20;
1.39 +const size_t ChunkSize = size_t(1) << ChunkShift;
1.40 +const size_t ChunkMask = ChunkSize - 1;
1.41 +
1.42 +const size_t CellShift = 3;
1.43 +const size_t CellSize = size_t(1) << CellShift;
1.44 +const size_t CellMask = CellSize - 1;
1.45 +
1.46 +/* These are magic constants derived from actual offsets in gc/Heap.h. */
1.47 +const size_t ChunkMarkBitmapOffset = 1032360;
1.48 +const size_t ChunkMarkBitmapBits = 129024;
1.49 +const size_t ChunkRuntimeOffset = ChunkSize - sizeof(void*);
1.50 +const size_t ChunkLocationOffset = ChunkSize - sizeof(void*) - sizeof(uintptr_t);
1.51 +
1.52 +/*
1.53 + * Live objects are marked black. How many other additional colors are available
1.54 + * depends on the size of the GCThing. Objects marked gray are eligible for
1.55 + * cycle collection.
1.56 + */
1.57 +static const uint32_t BLACK = 0;
1.58 +static const uint32_t GRAY = 1;
1.59 +
1.60 +/*
1.61 + * Constants used to indicate whether a chunk is part of the tenured heap or the
1.62 + * nusery.
1.63 + */
1.64 +const uintptr_t ChunkLocationNursery = 0;
1.65 +const uintptr_t ChunkLocationTenuredHeap = 1;
1.66 +
1.67 +} /* namespace gc */
1.68 +} /* namespace js */
1.69 +
1.70 +namespace JS {
1.71 +struct Zone;
1.72 +} /* namespace JS */
1.73 +
1.74 +namespace JS {
1.75 +namespace shadow {
1.76 +
1.77 +struct ArenaHeader
1.78 +{
1.79 + JS::Zone *zone;
1.80 +};
1.81 +
1.82 +struct Zone
1.83 +{
1.84 + protected:
1.85 + JSRuntime *const runtime_;
1.86 + JSTracer *const barrierTracer_; // A pointer to the JSRuntime's |gcMarker|.
1.87 +
1.88 + public:
1.89 + bool needsBarrier_;
1.90 +
1.91 + Zone(JSRuntime *runtime, JSTracer *barrierTracerArg)
1.92 + : runtime_(runtime),
1.93 + barrierTracer_(barrierTracerArg),
1.94 + needsBarrier_(false)
1.95 + {}
1.96 +
1.97 + bool needsBarrier() const {
1.98 + return needsBarrier_;
1.99 + }
1.100 +
1.101 + JSTracer *barrierTracer() {
1.102 + MOZ_ASSERT(needsBarrier_);
1.103 + MOZ_ASSERT(js::CurrentThreadCanAccessRuntime(runtime_));
1.104 + return barrierTracer_;
1.105 + }
1.106 +
1.107 + JSRuntime *runtimeFromMainThread() const {
1.108 + MOZ_ASSERT(js::CurrentThreadCanAccessRuntime(runtime_));
1.109 + return runtime_;
1.110 + }
1.111 +
1.112 + // Note: Unrestricted access to the zone's runtime from an arbitrary
1.113 + // thread can easily lead to races. Use this method very carefully.
1.114 + JSRuntime *runtimeFromAnyThread() const {
1.115 + return runtime_;
1.116 + }
1.117 +
1.118 + static JS::shadow::Zone *asShadowZone(JS::Zone *zone) {
1.119 + return reinterpret_cast<JS::shadow::Zone*>(zone);
1.120 + }
1.121 +};
1.122 +
1.123 +} /* namespace shadow */
1.124 +} /* namespace JS */
1.125 +
1.126 +namespace js {
1.127 +namespace gc {
1.128 +
1.129 +static MOZ_ALWAYS_INLINE uintptr_t *
1.130 +GetGCThingMarkBitmap(const void *thing)
1.131 +{
1.132 + MOZ_ASSERT(thing);
1.133 + uintptr_t addr = uintptr_t(thing);
1.134 + addr &= ~js::gc::ChunkMask;
1.135 + addr |= js::gc::ChunkMarkBitmapOffset;
1.136 + return reinterpret_cast<uintptr_t *>(addr);
1.137 +}
1.138 +
1.139 +static MOZ_ALWAYS_INLINE JS::shadow::Runtime *
1.140 +GetGCThingRuntime(const void *thing)
1.141 +{
1.142 + MOZ_ASSERT(thing);
1.143 + uintptr_t addr = uintptr_t(thing);
1.144 + addr &= ~js::gc::ChunkMask;
1.145 + addr |= js::gc::ChunkRuntimeOffset;
1.146 + return *reinterpret_cast<JS::shadow::Runtime **>(addr);
1.147 +}
1.148 +
1.149 +static MOZ_ALWAYS_INLINE void
1.150 +GetGCThingMarkWordAndMask(const void *thing, uint32_t color,
1.151 + uintptr_t **wordp, uintptr_t *maskp)
1.152 +{
1.153 + uintptr_t addr = uintptr_t(thing);
1.154 + size_t bit = (addr & js::gc::ChunkMask) / js::gc::CellSize + color;
1.155 + MOZ_ASSERT(bit < js::gc::ChunkMarkBitmapBits);
1.156 + uintptr_t *bitmap = GetGCThingMarkBitmap(thing);
1.157 + const uintptr_t nbits = sizeof(*bitmap) * CHAR_BIT;
1.158 + *maskp = uintptr_t(1) << (bit % nbits);
1.159 + *wordp = &bitmap[bit / nbits];
1.160 +}
1.161 +
1.162 +static MOZ_ALWAYS_INLINE JS::shadow::ArenaHeader *
1.163 +GetGCThingArena(void *thing)
1.164 +{
1.165 + uintptr_t addr = uintptr_t(thing);
1.166 + addr &= ~js::gc::ArenaMask;
1.167 + return reinterpret_cast<JS::shadow::ArenaHeader *>(addr);
1.168 +}
1.169 +
1.170 +MOZ_ALWAYS_INLINE bool
1.171 +IsInsideNursery(const JS::shadow::Runtime *runtime, const void *p)
1.172 +{
1.173 +#ifdef JSGC_GENERATIONAL
1.174 + return uintptr_t(p) >= runtime->gcNurseryStart_ && uintptr_t(p) < runtime->gcNurseryEnd_;
1.175 +#else
1.176 + return false;
1.177 +#endif
1.178 +}
1.179 +
1.180 +MOZ_ALWAYS_INLINE bool
1.181 +IsInsideNursery(const js::gc::Cell *cell)
1.182 +{
1.183 +#ifdef JSGC_GENERATIONAL
1.184 + if (!cell)
1.185 + return false;
1.186 + uintptr_t addr = uintptr_t(cell);
1.187 + addr &= ~js::gc::ChunkMask;
1.188 + addr |= js::gc::ChunkLocationOffset;
1.189 + uint32_t location = *reinterpret_cast<uint32_t *>(addr);
1.190 + JS_ASSERT(location == gc::ChunkLocationNursery ||
1.191 + location == gc::ChunkLocationTenuredHeap);
1.192 + return location == gc::ChunkLocationNursery;
1.193 +#else
1.194 + return false;
1.195 +#endif
1.196 +}
1.197 +
1.198 +} /* namespace gc */
1.199 +
1.200 +} /* namespace js */
1.201 +
1.202 +namespace JS {
1.203 +
1.204 +static MOZ_ALWAYS_INLINE Zone *
1.205 +GetGCThingZone(void *thing)
1.206 +{
1.207 + MOZ_ASSERT(thing);
1.208 + return js::gc::GetGCThingArena(thing)->zone;
1.209 +}
1.210 +
1.211 +static MOZ_ALWAYS_INLINE Zone *
1.212 +GetObjectZone(JSObject *obj)
1.213 +{
1.214 + return GetGCThingZone(obj);
1.215 +}
1.216 +
1.217 +static MOZ_ALWAYS_INLINE bool
1.218 +GCThingIsMarkedGray(void *thing)
1.219 +{
1.220 +#ifdef JSGC_GENERATIONAL
1.221 + /*
1.222 + * GC things residing in the nursery cannot be gray: they have no mark bits.
1.223 + * All live objects in the nursery are moved to tenured at the beginning of
1.224 + * each GC slice, so the gray marker never sees nursery things.
1.225 + */
1.226 + JS::shadow::Runtime *rt = js::gc::GetGCThingRuntime(thing);
1.227 + if (js::gc::IsInsideNursery(rt, thing))
1.228 + return false;
1.229 +#endif
1.230 + uintptr_t *word, mask;
1.231 + js::gc::GetGCThingMarkWordAndMask(thing, js::gc::GRAY, &word, &mask);
1.232 + return *word & mask;
1.233 +}
1.234 +
1.235 +static MOZ_ALWAYS_INLINE bool
1.236 +IsIncrementalBarrierNeededOnGCThing(shadow::Runtime *rt, void *thing, JSGCTraceKind kind)
1.237 +{
1.238 + if (!rt->needsBarrier_)
1.239 + return false;
1.240 + JS::Zone *zone = GetGCThingZone(thing);
1.241 + return reinterpret_cast<shadow::Zone *>(zone)->needsBarrier_;
1.242 +}
1.243 +
1.244 +} /* namespace JS */
1.245 +
1.246 +#endif /* js_HeapAPI_h */
