Allow monomorphic loads when static type is known.

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 6778 matching lines @@
     instr = new(zone()) HStringCharFromCode(context, char_code);
 
   } else if (expr->IsFunctionPrototype()) {
     HValue* function = Pop();
     AddInstruction(new(zone()) HCheckNonSmi(function));
     instr = new(zone()) HLoadFunctionPrototype(function);
 
   } else if (expr->key()->IsPropertyName()) {
     Handle<String> name = expr->key()->AsLiteral()->AsPropertyName();
     SmallMapList* types = expr->GetReceiverTypes();
+    HValue* object = Top();
 
-    bool monomorphic = expr->IsMonomorphic();
     Handle<Map> map;
+    bool monomorphic = false;
     if (expr->IsMonomorphic()) {
       map = types->first();
-      if (map->is_dictionary_map()) monomorphic = false;
+      monomorphic = !map->is_dictionary_map();
+    } else if (object->HasMonomorphicJSObjectType()) {
+      map = object->GetMonomorphicJSObjectMap();
+      monomorphic = !map->is_dictionary_map();
     }
     if (monomorphic) {
       Handle<JSFunction> getter;
       Handle<JSObject> holder;
       if (LookupGetter(map, name, &getter, &holder)) {
         AddCheckConstantFunction(holder, Top(), map);
         if (FLAG_inline_accessors && TryInlineGetter(getter, expr)) return;
         AddInstruction(new(zone()) HPushArgument(Pop()));
         instr = new(zone()) HCallConstantFunction(getter, 1);
       } else {
@@ skipping 3492 matching lines @@
     }
   }
 
 #ifdef DEBUG
   if (graph_ != NULL) graph_->Verify(false);  // No full verify.
   if (allocator_ != NULL) allocator_->Verify();
 #endif
 }
 
 } }  // namespace v8::internal