Enable GVN for polymorphic loads by not expanding them at the HIR level.

src/arm/lithium-arm.cc

 // Copyright 2011 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 1755 matching lines @@
   return new LStoreContextSlot(context, value);
 }
 
 
 LInstruction* LChunkBuilder::DoLoadNamedField(HLoadNamedField* instr) {
   return DefineAsRegister(
       new LLoadNamedField(UseRegisterAtStart(instr->object())));
 }
 
 
+LInstruction* LChunkBuilder::DoLoadNamedFieldPolymorphic(
+    HLoadNamedFieldPolymorphic* instr) {
+  ASSERT(instr->representation().IsTagged());
+  if (instr->need_generic()) {
+    LOperand* obj = UseFixed(instr->object(), r0);
+    LLoadNamedFieldPolymorphic* result = new LLoadNamedFieldPolymorphic(obj);
+    return MarkAsCall(DefineFixed(result, r0), instr);
+  } else {
+    LOperand* obj = UseRegisterAtStart(instr->object());
+    LLoadNamedFieldPolymorphic* result = new LLoadNamedFieldPolymorphic(obj);
+    return AssignEnvironment(DefineAsRegister(result));
+  }
+}
+
+
 LInstruction* LChunkBuilder::DoLoadNamedGeneric(HLoadNamedGeneric* instr) {
   LOperand* object = UseFixed(instr->object(), r0);
   LInstruction* result = DefineFixed(new LLoadNamedGeneric(object), r0);
   return MarkAsCall(result, instr);
 }
 
 
 LInstruction* LChunkBuilder::DoLoadFunctionPrototype(
     HLoadFunctionPrototype* instr) {
   return AssignEnvironment(DefineAsRegister(
@@ skipping 285 matching lines @@
 
 
 LInstruction* LChunkBuilder::DoLeaveInlined(HLeaveInlined* instr) {
   HEnvironment* outer = current_block_->last_environment()->outer();
   current_block_->UpdateEnvironment(outer);
   return NULL;
 }
 
 
 } }  // namespace v8::internal