Bug 878160 - GC: post barrier weak references in the browser - part 1 JS engine r=terrence

--HG--
extra : rebase_source : 4dfd4f8f46564d3a9858646a0f68c9047c2f7e93

js/public/HashTable.h

@@ -255,6 +255,14 @@ class HashMap
             remove(p);
     }
 
+    // Infallibly rekey one entry, if present.
+    void rekey(const Lookup &old_key, const Key &new_key) {
+        if (old_key != new_key) {
+            if (Ptr p = lookup(old_key))
+                impl.rekey(p, new_key, new_key);
+        }
+    }
+
     // HashMap is movable
     HashMap(MoveRef<HashMap> rhs) : impl(Move(rhs->impl)) {}
     void operator=(MoveRef<HashMap> rhs) { impl = Move(rhs->impl); }
@@ -802,10 +810,7 @@ class HashTable : private AllocPolicy
         // a new key at the new Lookup position.  |front()| is invalid after
         // this operation until the next call to |popFront()|.
         void rekeyFront(const Lookup &l, const Key &k) {
-            typename HashTableEntry<T>::NonConstT t(Move(this->cur->get()));
-            HashPolicy::setKey(t, const_cast<Key &>(k));
-            table.remove(*this->cur);
-            table.putNewInfallible(l, Move(t));
+            table.rekey(*this->cur, l, k);
             rekeyed = true;
             this->validEntry = false;
         }
@@ -1453,6 +1458,17 @@ class HashTable : private AllocPolicy
         checkUnderloaded();
     }
 
+    void rekey(Ptr p, const Lookup &l, const Key &k)
+    {
+        JS_ASSERT(table);
+        ReentrancyGuard g(*this);
+        JS_ASSERT(p.found());
+        typename HashTableEntry<T>::NonConstT t(Move(*p));
+        HashPolicy::setKey(t, const_cast<Key &>(k));
+        remove(*p.entry_);
+        putNewInfallible(l, Move(t));
+    }
+
 #undef METER
 };
 

js/public/RootingAPI.h

@@ -203,8 +203,11 @@ class Heap : public js::HeapBase<T>
             relocate();
     }
 
-    bool operator!=(const T &other) const { return ptr != other; }
+    bool operator==(const Heap<T> &other) { return ptr == other.ptr; }
+    bool operator!=(const Heap<T> &other) { return ptr != other.ptr; }
+
     bool operator==(const T &other) const { return ptr == other; }
+    bool operator!=(const T &other) const { return ptr != other; }
 
     operator T() const { return ptr; }
     T operator->() const { return ptr; }

js/src/gc/StoreBuffer.h

@@ -212,6 +212,9 @@ class StoreBuffer
         void put(const T &t) {
             JS_ASSERT(!owner->inParallelSection());
 
+            /* Ensure T is derived from BufferableRef. */
+            (void)static_cast<const BufferableRef*>(&t);
+
             /* Check if we have been enabled. */
             if (!pos)
                 return;
@@ -348,6 +351,22 @@ class StoreBuffer
         void mark(JSTracer *trc);
     };
 
+    class CallbackRef : public BufferableRef
+    {
+      public:
+        typedef void (*MarkCallback)(JSTracer *trc, void *key);
+
+        CallbackRef(MarkCallback cb, void *k) : callback(cb), key(k) {}
+
+        virtual void mark(JSTracer *trc) {
+            callback(trc, key);
+        }
+
+      private:
+        MarkCallback callback;
+        void *key;
+    };
+
     MonoTypeBuffer<ValueEdge> bufferVal;
     MonoTypeBuffer<CellPtrEdge> bufferCell;
     MonoTypeBuffer<SlotEdge> bufferSlot;
@@ -429,6 +448,11 @@ class StoreBuffer
         bufferGeneric.put(t);
     }
 
+    /* Insert or update a callback entry. */
+    void putCallback(CallbackRef::MarkCallback callback, void *key) {
+        bufferGeneric.put(CallbackRef(callback, key));
+    }
+
     /* Mark the source of all edges in the store buffer. */
     void mark(JSTracer *trc);
 

js/src/jsfriendapi.cpp

@@ -1123,3 +1123,11 @@ js::IsInRequest(JSContext *cx)
     return !!cx->runtime()->requestDepth;
 }
 #endif
+
+#ifdef JSGC_GENERATIONAL
+JS_FRIEND_API(void)
+JS_StorePostBarrierCallback(JSContext* cx, void (*callback)(JSTracer *trc, void *key), void *key)
+{
+    cx->runtime()->gcStoreBuffer.putCallback(callback, key);
+}
+#endif /* JSGC_GENERATIONAL */

js/src/jsfriendapi.h

@@ -1762,4 +1762,12 @@ js_DefineOwnProperty(JSContext *cx, JSObject *objArg, jsid idArg,
 extern JS_FRIEND_API(JSBool)
 js_ReportIsNotFunction(JSContext *cx, const JS::Value& v);
 
+#ifdef JSGC_GENERATIONAL
+extern JS_FRIEND_API(void)
+JS_StorePostBarrierCallback(JSContext* cx, void (*callback)(JSTracer *trc, void *key), void *key);
+#else
+inline void
+JS_StorePostBarrierCallback(JSContext* cx, void (*callback)(JSTracer *trc, void *key), void *key) {}
+#endif /* JSGC_GENERATIONAL */
+
 #endif /* jsfriendapi_h */