Bug 1224038 - Part 1: Add infallible versions of uid and hashcode getters; r=sfink

--HG--
extra : rebase_source : 5cc9c195abd671ce06ba196b7da7c7b8c29fde08

js/src/gc/Barrier.cpp

@@ -125,11 +125,7 @@ MovableCellHasher<T>::hash(const Lookup& l)
     MOZ_ASSERT(CurrentThreadCanAccessZone(l->zoneFromAnyThread()) ||
                l->zoneFromAnyThread()->isSelfHostingZone());
 
-    HashNumber hn;
-    AutoEnterOOMUnsafeRegion oomUnsafe;
-    if (!l->zoneFromAnyThread()->getHashCode(l, &hn))
-        oomUnsafe.crash("failed to get a stable hash code");
-    return hn;
+    return l->zoneFromAnyThread()->getHashCodeInfallible(l);
 }
 
 template <typename T>
@@ -154,10 +150,7 @@ MovableCellHasher<T>::match(const Key& k, const Lookup& l)
     MOZ_ASSERT(zone->hasUniqueId(l));
 
     // Since both already have a uid (from hash), the get is infallible.
-    uint64_t uidK, uidL;
-    MOZ_ALWAYS_TRUE(zone->getUniqueId(k, &uidK));
-    MOZ_ALWAYS_TRUE(zone->getUniqueId(l, &uidL));
-    return uidK == uidL;
+    return zone->getUniqueIdInfallible(k) == zone->getUniqueIdInfallible(l);
 }
 
 template struct MovableCellHasher<JSObject*>;

js/src/gc/Zone.h

@@ -360,12 +360,16 @@ struct Zone : public JS::shadow::Zone,
     unsigned gcLastZoneGroupIndex;
 #endif
 
+    static js::HashNumber UniqueIdToHash(uint64_t uid) {
+        return js::HashNumber(uid >> 32) ^ js::HashNumber(uid & 0xFFFFFFFF);
+    }
+
     // Creates a HashNumber based on getUniqueId. Returns false on OOM.
     MOZ_WARN_UNUSED_RESULT bool getHashCode(js::gc::Cell* cell, js::HashNumber* hashp) {
         uint64_t uid;
         if (!getUniqueId(cell, &uid))
             return false;
-        *hashp = js::HashNumber(uid >> 32) ^ js::HashNumber(uid & 0xFFFFFFFF);
+        *hashp = UniqueIdToHash(uid);
         return true;
     }
 
@@ -390,10 +394,19 @@ struct Zone : public JS::shadow::Zone,
         // If the cell was in the nursery, hopefully unlikely, then we need to
         // tell the nursery about it so that it can sweep the uid if the thing
         // does not get tenured.
+        return runtimeFromAnyThread()->gc.nursery.addedUniqueIdToCell(cell);
+    }
+
+    js::HashNumber getHashCodeInfallible(js::gc::Cell* cell) {
+        return UniqueIdToHash(getUniqueIdInfallible(cell));
+    }
+
+    uint64_t getUniqueIdInfallible(js::gc::Cell* cell) {
+        uint64_t uid;
         js::AutoEnterOOMUnsafeRegion oomUnsafe;
-        if (!runtimeFromAnyThread()->gc.nursery.addedUniqueIdToCell(cell))
-            oomUnsafe.crash("failed to allocate tracking data for a nursery uid");
-        return true;
+        if (!getUniqueId(cell, &uid))
+            oomUnsafe.crash("failed to allocate uid");
+        return uid;
     }
 
     // Return true if this cell has a UID associated with it.