Drop useless HForceRepresentation in BinaryOpStub.

src/code-stubs-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 914 matching lines @@
             Add<HConstant>(static_cast<int>(SmiValuesAre32Bits()
                 ? 0x80000000 : 0x40000000)), Token::EQ_STRICT);
         if_of.Then();
         if_of.ElseDeopt("UInt->Smi oveflow");
         if_of.End();
       }
     }
     result = EnforceNumberType(result, result_type);
   }
 
-  // Reuse the double box if we are allowed to (i.e. chained binops).
+  // Reuse the double box of one of the operands if we are allowed to (i.e.
+  // chained binops).
   if (stub->CanReuseDoubleBox()) {
-    HValue* reuse = (stub->mode() == OVERWRITE_LEFT) ? left : right;
+    HValue* operand = (stub->mode() == OVERWRITE_LEFT) ? left : right;
     IfBuilder if_heap_number(this);
-    if_heap_number.IfNot<HIsSmiAndBranch>(reuse);
+    if_heap_number.IfNot<HIsSmiAndBranch>(operand);
     if_heap_number.Then();
-    HValue* res_val = Add<HForceRepresentation>(result,
-                                                Representation::Double());
-    HObjectAccess access = HObjectAccess::ForHeapNumberValue();
-    Add<HStoreNamedField>(reuse, access, res_val);
-    Push(reuse);
+    Add<HStoreNamedField>(operand, HObjectAccess::ForHeapNumberValue(), result);
+    Push(operand);
     if_heap_number.Else();
     Push(result);
     if_heap_number.End();
     result = Pop();
   }
 
   return result;
 }
 
 
@@ skipping 288 matching lines @@
   return js_function;
 }
 
 
 Handle<Code> FastNewClosureStub::GenerateCode(Isolate* isolate) {
   return DoGenerateCode(isolate, this);
 }
 
 
 } }  // namespace v8::internal