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diff --git a/js/src/vm/Caches.h b/js/src/vm/Caches.h
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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/. */
+
+#ifndef vm_Caches_h
+#define vm_Caches_h
+
+#include "jsatom.h"
+#include "jsbytecode.h"
+#include "jsobj.h"
+#include "jsscript.h"
+
+#include "ds/FixedSizeHash.h"
+#include "frontend/SourceNotes.h"
+#include "gc/Tracer.h"
+#include "js/RootingAPI.h"
+#include "js/UniquePtr.h"
+#include "vm/NativeObject.h"
+
+namespace js {
+
+/*
+ * GetSrcNote cache to avoid O(n^2) growth in finding a source note for a
+ * given pc in a script. We use the script->code pointer to tag the cache,
+ * instead of the script address itself, so that source notes are always found
+ * by offset from the bytecode with which they were generated.
+ */
+struct GSNCache {
+    typedef HashMap<jsbytecode*,
+                    jssrcnote*,
+                    PointerHasher<jsbytecode*, 0>,
+                    SystemAllocPolicy> Map;
+
+    jsbytecode*     code;
+    Map             map;
+
+    GSNCache() : code(nullptr) { }
+
+    void purge();
+};
+
+/*
+ * EnvironmentCoordinateName cache to avoid O(n^2) growth in finding the name
+ * associated with a given aliasedvar operation.
+ */
+struct EnvironmentCoordinateNameCache {
+    typedef HashMap<uint32_t,
+                    jsid,
+                    DefaultHasher<uint32_t>,
+                    SystemAllocPolicy> Map;
+
+    Shape* shape;
+    Map map;
+
+    EnvironmentCoordinateNameCache() : shape(nullptr) {}
+    void purge();
+};
+
+struct EvalCacheEntry
+{
+    JSLinearString* str;
+    JSScript* script;
+    JSScript* callerScript;
+    jsbytecode* pc;
+};
+
+struct EvalCacheLookup
+{
+    explicit EvalCacheLookup(JSContext* cx) : str(cx), callerScript(cx) {}
+    RootedLinearString str;
+    RootedScript callerScript;
+    JSVersion version;
+    jsbytecode* pc;
+};
+
+struct EvalCacheHashPolicy
+{
+    typedef EvalCacheLookup Lookup;
+
+    static HashNumber hash(const Lookup& l);
+    static bool match(const EvalCacheEntry& entry, const EvalCacheLookup& l);
+};
+
+typedef HashSet<EvalCacheEntry, EvalCacheHashPolicy, SystemAllocPolicy> EvalCache;
+
+struct LazyScriptHashPolicy
+{
+    struct Lookup {
+        JSContext* cx;
+        LazyScript* lazy;
+
+        Lookup(JSContext* cx, LazyScript* lazy)
+          : cx(cx), lazy(lazy)
+        {}
+    };
+
+    static const size_t NumHashes = 3;
+
+    static void hash(const Lookup& lookup, HashNumber hashes[NumHashes]);
+    static bool match(JSScript* script, const Lookup& lookup);
+
+    // Alternate methods for use when removing scripts from the hash without an
+    // explicit LazyScript lookup.
+    static void hash(JSScript* script, HashNumber hashes[NumHashes]);
+    static bool match(JSScript* script, JSScript* lookup) { return script == lookup; }
+
+    static void clear(JSScript** pscript) { *pscript = nullptr; }
+    static bool isCleared(JSScript* script) { return !script; }
+};
+
+typedef FixedSizeHashSet<JSScript*, LazyScriptHashPolicy, 769> LazyScriptCache;
+
+class PropertyIteratorObject;
+
+class NativeIterCache
+{
+    static const size_t SIZE = size_t(1) << 8;
+
+    /* Cached native iterators. */
+    PropertyIteratorObject* data[SIZE];
+
+    static size_t getIndex(uint32_t key) {
+        return size_t(key) % SIZE;
+    }
+
+  public:
+    NativeIterCache() {
+        mozilla::PodArrayZero(data);
+    }
+
+    void purge() {
+        mozilla::PodArrayZero(data);
+    }
+
+    PropertyIteratorObject* get(uint32_t key) const {
+        return data[getIndex(key)];
+    }
+
+    void set(uint32_t key, PropertyIteratorObject* iterobj) {
+        data[getIndex(key)] = iterobj;
+    }
+};
+
+/*
+ * Cache for speeding up repetitive creation of objects in the VM.
+ * When an object is created which matches the criteria in the 'key' section
+ * below, an entry is filled with the resulting object.
+ */
+class NewObjectCache
+{
+    /* Statically asserted to be equal to sizeof(JSObject_Slots16) */
+    static const unsigned MAX_OBJ_SIZE = 4 * sizeof(void*) + 16 * sizeof(Value);
+
+    static void staticAsserts() {
+        JS_STATIC_ASSERT(NewObjectCache::MAX_OBJ_SIZE == sizeof(JSObject_Slots16));
+        JS_STATIC_ASSERT(gc::AllocKind::OBJECT_LAST == gc::AllocKind::OBJECT16_BACKGROUND);
+    }
+
+    struct Entry
+    {
+        /* Class of the constructed object. */
+        const Class* clasp;
+
+        /*
+         * Key with one of three possible values:
+         *
+         * - Global for the object. The object must have a standard class for
+         *   which the global's prototype can be determined, and the object's
+         *   parent will be the global.
+         *
+         * - Prototype for the object (cannot be global). The object's parent
+         *   will be the prototype's parent.
+         *
+         * - Type for the object. The object's parent will be the type's
+         *   prototype's parent.
+         */
+        gc::Cell* key;
+
+        /* Allocation kind for the constructed object. */
+        gc::AllocKind kind;
+
+        /* Number of bytes to copy from the template object. */
+        uint32_t nbytes;
+
+        /*
+         * Template object to copy from, with the initial values of fields,
+         * fixed slots (undefined) and private data (nullptr).
+         */
+        char templateObject[MAX_OBJ_SIZE];
+    };
+
+    Entry entries[41];  // TODO: reconsider size
+
+  public:
+
+    typedef int EntryIndex;
+
+    NewObjectCache() { mozilla::PodZero(this); }
+    void purge() { mozilla::PodZero(this); }
+
+    /* Remove any cached items keyed on moved objects. */
+    void clearNurseryObjects(JSRuntime* rt);
+
+    /*
+     * Get the entry index for the given lookup, return whether there was a hit
+     * on an existing entry.
+     */
+    inline bool lookupProto(const Class* clasp, JSObject* proto, gc::AllocKind kind, EntryIndex* pentry);
+    inline bool lookupGlobal(const Class* clasp, js::GlobalObject* global, gc::AllocKind kind,
+                             EntryIndex* pentry);
+
+    bool lookupGroup(js::ObjectGroup* group, gc::AllocKind kind, EntryIndex* pentry) {
+        return lookup(group->clasp(), group, kind, pentry);
+    }
+
+    /*
+     * Return a new object from a cache hit produced by a lookup method, or
+     * nullptr if returning the object could possibly trigger GC (does not
+     * indicate failure).
+     */
+    inline NativeObject* newObjectFromHit(JSContext* cx, EntryIndex entry, js::gc::InitialHeap heap);
+
+    /* Fill an entry after a cache miss. */
+    void fillProto(EntryIndex entry, const Class* clasp, js::TaggedProto proto,
+                   gc::AllocKind kind, NativeObject* obj);
+
+    inline void fillGlobal(EntryIndex entry, const Class* clasp, js::GlobalObject* global,
+                           gc::AllocKind kind, NativeObject* obj);
+
+    void fillGroup(EntryIndex entry, js::ObjectGroup* group, gc::AllocKind kind,
+                   NativeObject* obj)
+    {
+        MOZ_ASSERT(obj->group() == group);
+        return fill(entry, group->clasp(), group, kind, obj);
+    }
+
+    /* Invalidate any entries which might produce an object with shape/proto. */
+    void invalidateEntriesForShape(JSContext* cx, HandleShape shape, HandleObject proto);
+
+  private:
+    EntryIndex makeIndex(const Class* clasp, gc::Cell* key, gc::AllocKind kind) {
+        uintptr_t hash = (uintptr_t(clasp) ^ uintptr_t(key)) + size_t(kind);
+        return hash % mozilla::ArrayLength(entries);
+    }
+
+    bool lookup(const Class* clasp, gc::Cell* key, gc::AllocKind kind, EntryIndex* pentry) {
+        *pentry = makeIndex(clasp, key, kind);
+        Entry* entry = &entries[*pentry];
+
+        /* N.B. Lookups with the same clasp/key but different kinds map to different entries. */
+        return entry->clasp == clasp && entry->key == key;
+    }
+
+    void fill(EntryIndex entry_, const Class* clasp, gc::Cell* key, gc::AllocKind kind,
+              NativeObject* obj) {
+        MOZ_ASSERT(unsigned(entry_) < mozilla::ArrayLength(entries));
+        MOZ_ASSERT(entry_ == makeIndex(clasp, key, kind));
+        Entry* entry = &entries[entry_];
+
+        entry->clasp = clasp;
+        entry->key = key;
+        entry->kind = kind;
+
+        entry->nbytes = gc::Arena::thingSize(kind);
+        js_memcpy(&entry->templateObject, obj, entry->nbytes);
+    }
+
+    static void copyCachedToObject(NativeObject* dst, NativeObject* src, gc::AllocKind kind) {
+        js_memcpy(dst, src, gc::Arena::thingSize(kind));
+        Shape::writeBarrierPost(&dst->shape_, nullptr, dst->shape_);
+        ObjectGroup::writeBarrierPost(&dst->group_, nullptr, dst->group_);
+    }
+};
+
+class MathCache;
+
+class ContextCaches
+{
+    UniquePtr<js::MathCache> mathCache_;
+
+    js::MathCache* createMathCache(JSContext* cx);
+
+  public:
+    js::GSNCache gsnCache;
+    js::EnvironmentCoordinateNameCache envCoordinateNameCache;
+    js::NewObjectCache newObjectCache;
+    js::NativeIterCache nativeIterCache;
+    js::UncompressedSourceCache uncompressedSourceCache;
+    js::EvalCache evalCache;
+    js::LazyScriptCache lazyScriptCache;
+
+    bool init();
+
+    js::MathCache* getMathCache(JSContext* cx) {
+        return mathCache_ ? mathCache_.get() : createMathCache(cx);
+    }
+    js::MathCache* maybeGetMathCache() {
+        return mathCache_.get();
+    }
+};
+
+} // namespace js
+
+#endif /* vm_Caches_h */