Fix "Hole" leak in TryBuildConsolidatedElementLoad

src/hydrogen.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 5511 matching lines @@
     HValue* val,
     SmallMapList* maps) {
   // For polymorphic loads of similar elements kinds (i.e. all tagged or all
   // double), always use the "worst case" code without a transition.  This is
   // much faster than transitioning the elements to the worst case, trading a
   // HTransitionElements for a HCheckMaps, and avoiding mutation of the array.
   bool has_double_maps = false;
   bool has_smi_or_object_maps = false;
   bool has_js_array_access = false;
   bool has_non_js_array_access = false;
+  bool has_seen_holey_elements = false;
   Handle<Map> most_general_consolidated_map;
   for (int i = 0; i < maps->length(); ++i) {
     Handle<Map> map = maps->at(i);
     // Don't allow mixing of JSArrays with JSObjects.
     if (map->instance_type() == JS_ARRAY_TYPE) {
       if (has_non_js_array_access) return NULL;
       has_js_array_access = true;
     } else if (has_js_array_access) {
       return NULL;
     } else {
       has_non_js_array_access = true;
     }
     // Don't allow mixed, incompatible elements kinds.
     if (map->has_fast_double_elements()) {
       if (has_smi_or_object_maps) return NULL;
       has_double_maps = true;
     } else if (map->has_fast_smi_or_object_elements()) {
       if (has_double_maps) return NULL;
       has_smi_or_object_maps = true;
     } else {
       return NULL;
     }
+    // Remember if we've ever seen holey elements.
+    if (IsHoleyElementsKind(map->elements_kind())) {
+      has_seen_holey_elements = true;
+    }
     // Remember the most general elements kind, the code for its load will
     // properly handle all of the more specific cases.
     if ((i == 0) || IsMoreGeneralElementsKindTransition(
             most_general_consolidated_map->elements_kind(),
             map->elements_kind())) {
       most_general_consolidated_map = map;
     }
   }
   if (!has_double_maps && !has_smi_or_object_maps) return NULL;
 
   HCheckMaps* check_maps = Add<HCheckMaps>(object, maps);
+  // FAST_ELEMENTS is considered more general than FAST_HOLEY_SMI_ELEMENTS.
+  // If we've seen both, the consolidated load must use FAST_HOLEY_ELEMENTS.
+  ElementsKind consolidated_elements_kind = has_seen_holey_elements
+      ? GetHoleyElementsKind(most_general_consolidated_map->elements_kind())
+      : most_general_consolidated_map->elements_kind();
   HInstruction* instr = BuildUncheckedMonomorphicElementAccess(
       object, key, val, check_maps,
       most_general_consolidated_map->instance_type() == JS_ARRAY_TYPE,
-      most_general_consolidated_map->elements_kind(),
+      consolidated_elements_kind,
       false, NEVER_RETURN_HOLE, STANDARD_STORE);
   return instr;
 }
 
 
 HValue* HOptimizedGraphBuilder::HandlePolymorphicElementAccess(
     HValue* object,
     HValue* key,
     HValue* val,
     Expression* prop,
@@ skipping 4261 matching lines @@
   if (ShouldProduceTraceOutput()) {
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 } }  // namespace v8::internal