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

src/x64/lithium-codegen-x64.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 2774 matching lines @@
   __ movq(kScratchRegister, V8_INT64_C(0x3FE0000000000000), RelocInfo::NONE);
   __ movq(xmm_scratch, kScratchRegister);
   Label below_half;
   __ ucomisd(xmm_scratch, input_reg);
   // If input_reg is NaN, this doesn't jump.
   __ j(above, &below_half, Label::kNear);
   // input = input + 0.5
   // This addition might give a result that isn't the correct for
   // rounding, due to loss of precision, but only for a number that's
   // so big that the conversion below will overflow anyway.
-  __ addsd(input_reg, xmm_scratch);
+  __ addsd(xmm_scratch, input_reg);
   // Compute Math.floor(input).
   // Use truncating instruction (OK because input is positive).
-  __ cvttsd2si(output_reg, input_reg);
+  __ cvttsd2si(output_reg, xmm_scratch);
   // Overflow is signalled with minint.
   __ cmpl(output_reg, Immediate(0x80000000));
   DeoptimizeIf(equal, instr->environment());
   __ jmp(&done);
 
   __ bind(&below_half);
   if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
     // Bailout if negative (including -0).
     __ movq(output_reg, input_reg);
     __ testq(output_reg, output_reg);
@@ skipping 1499 matching lines @@
   RegisterEnvironmentForDeoptimization(environment, Safepoint::kNoLazyDeopt);
   ASSERT(osr_pc_offset_ == -1);
   osr_pc_offset_ = masm()->pc_offset();
 }
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64