Tweak HConstant::EmitAtUses() to eliminate useless constant generation

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 2508 matching lines @@
       r = Representation::Tagged();
     }
   }
   set_representation(r);
   SetFlag(kUseGVN);
 }
 
 
 bool HConstant::EmitAtUses() {
   ASSERT(IsLinked());
-  if (block()->graph()->has_osr()) {
-    return block()->graph()->IsStandardConstant(this);
+  if (block()->graph()->has_osr() &&
+      block()->graph()->IsStandardConstant(this)) {
+    return true;
   }
+  if (UseCount() == 0) return true;
   if (IsCell()) return false;
   if (representation().IsDouble()) return false;
   return true;
 }
 
 
 HConstant* HConstant::CopyToRepresentation(Representation r, Zone* zone) const {
   if (r.IsSmi() && !has_smi_value_) return NULL;
   if (r.IsInteger32() && !has_int32_value_) return NULL;
   if (r.IsDouble() && !has_double_value_) return NULL;
@@ skipping 1696 matching lines @@
       break;
     case kExternalMemory:
       stream->Add("[external-memory]");
       break;
   }
 
   stream->Add("@%d", offset());
 }
 
 } }  // namespace v8::internal