Fix polymorphic load on named fields.

src/hydrogen.cc

 // Copyright 2012 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 4011 matching lines @@
                              true)  // Needs smi and map check.
       : BuildStoreNamedGeneric(object, name, value);
 }
 
 
 void HGraphBuilder::HandlePolymorphicLoadNamedField(Property* expr,
                                                     HValue* object,
                                                     SmallMapList* types,
                                                     Handle<String> name) {
   int count = 0;
-  int previous_field_index = 0;
+  int previous_field_offset = 0;
+  bool previous_field_is_in_object = false;
   bool is_monomorphic_field = true;
   Handle<Map> map;
   LookupResult lookup(isolate());
   for (int i = 0; i < types->length() && count < kMaxLoadPolymorphism; ++i) {
     map = types->at(i);
     if (ComputeLoadStoreField(map, name, &lookup, false)) {
       int index = ComputeLoadStoreFieldIndex(map, name, &lookup);
+      bool is_in_object = index < 0;
+      int offset = index * kPointerSize;
+      if (index < 0) {
+        // Negative property indices are in-object properties, indexed
+        // from the end of the fixed part of the object.
+        offset += map->instance_size();
+      } else {
+        offset += FixedArray::kHeaderSize;
+      }
       if (count == 0) {
-        previous_field_index = index;
+        previous_field_offset = offset;
+        previous_field_is_in_object = is_in_object;
       } else if (is_monomorphic_field) {
-        is_monomorphic_field = (index == previous_field_index);
+        is_monomorphic_field = (offset == previous_field_offset) &&
+                               (is_in_object == previous_field_is_in_object);
       }
       ++count;
     }
   }
 
   // Use monomorphic load if property lookup results in the same field index
   // for all maps.  Requires special map check on the set of all handled maps.
   HInstruction* instr;
   if (count == types->length() && is_monomorphic_field) {
     AddInstruction(new(zone()) HCheckMaps(object, types));
@@ skipping 4143 matching lines @@
     }
   }
 
 #ifdef DEBUG
   if (graph_ != NULL) graph_->Verify(false);  // No full verify.
   if (allocator_ != NULL) allocator_->Verify();
 #endif
 }
 
 } }  // namespace v8::internal