Bug 697931 - Remove KidHashes when possible. r=luke.

js/public/HashTable.h

@@ -645,12 +645,16 @@ class HashTable : private AllocPolicy
         return entryCount;
     }
 
+    uint32 capacity() const {
+        return tableCapacity;
+    }
+
     uint32 generation() const {
         return gen;
     }
 
     /*
-     * This counts the HashTable's |table| array.  If |countMe| is true is also
+     * This counts the HashTable's |table| array.  If |countMe| is true it also
      * counts the HashTable object itself.
      */
     size_t sizeOf(JSUsableSizeFun usf, bool countMe) const {
@@ -1087,6 +1091,7 @@ class HashMap
     typedef typename Impl::Range Range;
     Range all() const                                 { return impl.all(); }
     size_t count() const                              { return impl.count(); }
+    size_t capacity() const                           { return impl.capacity(); }
     size_t sizeOf(JSUsableSizeFun usf, bool cm) const { return impl.sizeOf(usf, cm); }
 
     /*
@@ -1289,6 +1294,7 @@ class HashSet
     typedef typename Impl::Range Range;
     Range all() const                                 { return impl.all(); }
     size_t count() const                              { return impl.count(); }
+    size_t capacity() const                           { return impl.capacity(); }
     size_t sizeOf(JSUsableSizeFun usf, bool cm) const { return impl.sizeOf(usf, cm); }
 
     /*

js/src/jspropertytree.cpp

@@ -139,13 +139,24 @@ Shape::removeChild(Shape *child)
     JS_ASSERT(!JSID_IS_VOID(propid));
 
     KidsPointer *kidp = &kids;
+
     if (kidp->isShape()) {
         JS_ASSERT(kidp->toShape() == child);
-        kids.setNull();
+        kidp->setNull();
         return;
     }
 
-    kidp->toHash()->remove(child);
+    KidsHash *hash = kidp->toHash();
+    JS_ASSERT(hash->count() >= 2);      /* otherwise kidp->isShape() should be true */
+    hash->remove(child);
+    if (hash->count() == 1) {
+        /* Convert from HASH form back to SHAPE form. */
+        KidsHash::Range r = hash->all(); 
+        Shape *otherChild = r.front();
+        JS_ASSERT((r.popFront(), r.empty()));    /* No more elements! */
+        kidp->setShape(otherChild);
+        js::UnwantedForeground::delete_(hash);
+    }
 }
 
 Shape *

js/src/jsscope.h

@@ -647,7 +647,6 @@ struct Shape : public js::gc::Cell
 
     void finalize(JSContext *cx);
     void removeChild(js::Shape *child);
-    void removeChildSlowly(js::Shape *child);
 };
 
 struct EmptyShape : public js::Shape