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+/* -*- 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