Allow boundscheck elimination to work on Smi keys.

src/hydrogen-instructions.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 1040 matching lines @@
   int actual_scale = decomposition.scale() + scale();
 
   if (actual_offset != 0) {
     HConstant* add_offset = new(block()->graph()->zone()) HConstant(
         actual_offset, index()->representation());
     add_offset->InsertBefore(this);
     HInstruction* add = HAdd::New(block()->graph()->zone(),
         block()->graph()->GetInvalidContext(), current_index, add_offset);
     add->InsertBefore(this);
     add->AssumeRepresentation(index()->representation());
+    add->ClearFlag(kCanOverflow);
     current_index = add;
   }
 
   if (actual_scale != 0) {
     HConstant* sar_scale = new(block()->graph()->zone()) HConstant(
         actual_scale, index()->representation());
     sar_scale->InsertBefore(this);
     HInstruction* sar = HSar::New(block()->graph()->zone(),
         block()->graph()->GetInvalidContext(), current_index, sar_scale);
     sar->InsertBefore(this);
@@ skipping 2767 matching lines @@
     case kBackingStore:
       if (!name_.is_null()) stream->Add(*String::cast(*name_)->ToCString());
       stream->Add("[backing-store]");
       break;
   }
 
   stream->Add("@%d", offset());
 }
 
 } }  // namespace v8::internal