Fix a bug with register use in optimized Math.round.

src/ia32/lithium-codegen-ia32.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 2882 matching lines @@
   XMMRegister xmm_scratch = xmm0;
   Register output_reg = ToRegister(instr->result());
   XMMRegister input_reg = ToDoubleRegister(instr->value());
 
   Label below_half, done;
   // xmm_scratch = 0.5
   ExternalReference one_half = ExternalReference::address_of_one_half();
   __ movdbl(xmm_scratch, Operand::StaticVariable(one_half));
   __ ucomisd(xmm_scratch, input_reg);
   __ j(above, &below_half);
-  // input = input + 0.5
-  __ addsd(input_reg, xmm_scratch);
+  // xmm_scratch = input + 0.5
+  __ addsd(xmm_scratch, input_reg);
 
   // Compute Math.floor(value + 0.5).
   // Use truncating instruction (OK because input is positive).
-  __ cvttsd2si(output_reg, Operand(input_reg));
+  __ cvttsd2si(output_reg, Operand(xmm_scratch));
 
   // Overflow is signalled with minint.
   __ cmp(output_reg, 0x80000000u);
   DeoptimizeIf(equal, instr->environment());
   __ jmp(&done);
 
   __ bind(&below_half);
 
   // We return 0 for the input range [+0, 0.5[, or [-0.5, 0.5[ if
   // we can ignore the difference between a result of -0 and +0.
@@ skipping 1689 matching lines @@
       this, pointers, Safepoint::kLazyDeopt);
   __ InvokeBuiltin(Builtins::IN, CALL_FUNCTION, safepoint_generator);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32