diff options
Diffstat (limited to '')
| -rw-r--r-- | js/src/gc/Tenuring.h | 169 |
1 files changed, 169 insertions, 0 deletions
diff --git a/js/src/gc/Tenuring.h b/js/src/gc/Tenuring.h new file mode 100644 index 0000000000..34ef950e1d --- /dev/null +++ b/js/src/gc/Tenuring.h @@ -0,0 +1,169 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- + * vim: set ts=8 sts=2 et sw=2 tw=80: + * 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_Tenuring_h +#define gc_Tenuring_h + +#include "mozilla/Maybe.h" + +#include "gc/AllocKind.h" +#include "js/GCAPI.h" +#include "js/TracingAPI.h" +#include "util/Text.h" + +namespace js { + +class NativeObject; +class Nursery; +class PlainObject; + +namespace gc { + +class RelocationOverlay; +class StringRelocationOverlay; + +template <typename Key> +struct DeduplicationStringHasher { + using Lookup = Key; + + static inline HashNumber hash(const Lookup& lookup) { + JS::AutoCheckCannotGC nogc; + HashNumber strHash; + + // Include flags in the hash. A string relocation overlay stores either + // the nursery root base chars or the dependent string nursery base, but + // does not indicate which one. If strings with different string types + // were deduplicated, for example, a dependent string gets deduplicated + // into an extensible string, the base chain would be broken and the root + // base would be unreachable. + + if (lookup->asLinear().hasLatin1Chars()) { + strHash = mozilla::HashString(lookup->asLinear().latin1Chars(nogc), + lookup->length()); + } else { + MOZ_ASSERT(lookup->asLinear().hasTwoByteChars()); + strHash = mozilla::HashString(lookup->asLinear().twoByteChars(nogc), + lookup->length()); + } + + return mozilla::HashGeneric(strHash, lookup->zone(), lookup->flags()); + } + + static MOZ_ALWAYS_INLINE bool match(const Key& key, const Lookup& lookup) { + if (!key->sameLengthAndFlags(*lookup) || + key->asTenured().zone() != lookup->zone() || + key->asTenured().getAllocKind() != lookup->getAllocKind()) { + return false; + } + + JS::AutoCheckCannotGC nogc; + + if (key->asLinear().hasLatin1Chars()) { + MOZ_ASSERT(lookup->asLinear().hasLatin1Chars()); + return EqualChars(key->asLinear().latin1Chars(nogc), + lookup->asLinear().latin1Chars(nogc), lookup->length()); + } else { + MOZ_ASSERT(key->asLinear().hasTwoByteChars()); + MOZ_ASSERT(lookup->asLinear().hasTwoByteChars()); + return EqualChars(key->asLinear().twoByteChars(nogc), + lookup->asLinear().twoByteChars(nogc), + lookup->length()); + } + } +}; + +class TenuringTracer final : public JSTracer { + Nursery& nursery_; + + // Amount of data moved to the tenured generation during collection. + size_t tenuredSize = 0; + // Number of cells moved to the tenured generation. + size_t tenuredCells = 0; + + // These lists are threaded through the Nursery using the space from + // already moved things. The lists are used to fix up the moved things and + // to find things held live by intra-Nursery pointers. + gc::RelocationOverlay* objHead = nullptr; + gc::StringRelocationOverlay* stringHead = nullptr; + + using StringDeDupSet = + HashSet<JSString*, DeduplicationStringHasher<JSString*>, + SystemAllocPolicy>; + + // deDupSet is emplaced at the beginning of the nursery collection and reset + // at the end of the nursery collection. It can also be reset during nursery + // collection when out of memory to insert new entries. + mozilla::Maybe<StringDeDupSet> stringDeDupSet; + +#define DEFINE_ON_EDGE_METHOD(name, type, _1, _2) \ + void on##name##Edge(type** thingp, const char* name) override; + JS_FOR_EACH_TRACEKIND(DEFINE_ON_EDGE_METHOD) +#undef DEFINE_ON_EDGE_METHOD + + public: + TenuringTracer(JSRuntime* rt, Nursery* nursery); + + Nursery& nursery() { return nursery_; } + + // Move all objects and everything they can reach to the tenured heap. Called + // after all roots have been traced. + void collectToObjectFixedPoint(); + + // Move all strings and all strings they can reach to the tenured heap, and + // additionally do any fixups for when strings are pointing into memory that + // was deduplicated. Called after collectToObjectFixedPoint(). + void collectToStringFixedPoint(); + + size_t getTenuredSize() const; + size_t getTenuredCells() const; + + void traverse(JS::Value* thingp); + + // The store buffers need to be able to call these directly. + void traceObject(JSObject* src); + void traceObjectSlots(NativeObject* nobj, uint32_t start, uint32_t end); + void traceSlots(JS::Value* vp, uint32_t nslots); + void traceString(JSString* src); + void traceBigInt(JS::BigInt* src); + + private: + // The dependent string chars needs to be relocated if the base which it's + // using chars from has been deduplicated. + template <typename CharT> + void relocateDependentStringChars(JSDependentString* tenuredDependentStr, + JSLinearString* baseOrRelocOverlay, + size_t* offset, + bool* rootBaseNotYetForwarded, + JSLinearString** rootBase); + + inline void insertIntoObjectFixupList(gc::RelocationOverlay* entry); + inline void insertIntoStringFixupList(gc::StringRelocationOverlay* entry); + + template <typename T> + inline T* allocTenured(JS::Zone* zone, gc::AllocKind kind); + JSString* allocTenuredString(JSString* src, JS::Zone* zone, + gc::AllocKind dstKind); + + inline JSObject* movePlainObjectToTenured(PlainObject* src); + JSObject* moveToTenuredSlow(JSObject* src); + JSString* moveToTenured(JSString* src); + JS::BigInt* moveToTenured(JS::BigInt* src); + + size_t moveElementsToTenured(NativeObject* dst, NativeObject* src, + gc::AllocKind dstKind); + size_t moveSlotsToTenured(NativeObject* dst, NativeObject* src); + size_t moveStringToTenured(JSString* dst, JSString* src, + gc::AllocKind dstKind); + size_t moveBigIntToTenured(JS::BigInt* dst, JS::BigInt* src, + gc::AllocKind dstKind); + + void traceSlots(JS::Value* vp, JS::Value* end); +}; + +} // namespace gc +} // namespace js + +#endif // gc_Tenuring_h |