Correctly retain argument value when deopting from Math.round on x64.

R=jkummerow@chromium.org
BUG=351624
LOG=N

Review URL: https://codereview.chromium.org/199013002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19896 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/x64/lithium-codegen-x64.cc

@@ -3604,10 +3604,11 @@ void LCodeGen::DoMathRound(LMathRound* instr) {
   const XMMRegister xmm_scratch = double_scratch0();
   Register output_reg = ToRegister(instr->result());
   XMMRegister input_reg = ToDoubleRegister(instr->value());
+  XMMRegister input_temp = ToDoubleRegister(instr->temp());
   static int64_t one_half = V8_INT64_C(0x3FE0000000000000);  // 0.5
   static int64_t minus_one_half = V8_INT64_C(0xBFE0000000000000);  // -0.5
 
-  Label done, round_to_zero, below_one_half, do_not_compensate, restore;
+  Label done, round_to_zero, below_one_half;
   Label::Distance dist = DeoptEveryNTimes() ? Label::kFar : Label::kNear;
   __ movq(kScratchRegister, one_half);
   __ movq(xmm_scratch, kScratchRegister);
@@ -3631,21 +3632,19 @@ void LCodeGen::DoMathRound(LMathRound* instr) {
 
   // CVTTSD2SI rounds towards zero, we use ceil(x - (-0.5)) and then
   // compare and compensate.
-  __ movq(kScratchRegister, input_reg);  // Back up input_reg.
-  __ subsd(input_reg, xmm_scratch);
-  __ cvttsd2si(output_reg, input_reg);
+  __ movq(input_temp, input_reg);  // Do not alter input_reg.
+  __ subsd(input_temp, xmm_scratch);
+  __ cvttsd2si(output_reg, input_temp);
   // Catch minint due to overflow, and to prevent overflow when compensating.
   __ cmpl(output_reg, Immediate(0x80000000));
   __ RecordComment("D2I conversion overflow");
   DeoptimizeIf(equal, instr->environment());
 
   __ Cvtlsi2sd(xmm_scratch, output_reg);
-  __ ucomisd(input_reg, xmm_scratch);
-  __ j(equal, &restore, Label::kNear);
+  __ ucomisd(xmm_scratch, input_temp);
+  __ j(equal, &done, dist);
   __ subl(output_reg, Immediate(1));
   // No overflow because we already ruled out minint.
-  __ bind(&restore);
-  __ movq(input_reg, kScratchRegister);  // Restore input_reg.
   __ jmp(&done, dist);
 
   __ bind(&round_to_zero);

src/x64/lithium-x64.cc

@@ -1133,8 +1133,9 @@ LInstruction* LChunkBuilder::DoMathFloor(HUnaryMathOperation* instr) {
 
 
 LInstruction* LChunkBuilder::DoMathRound(HUnaryMathOperation* instr) {
-  LOperand* input = UseRegisterAtStart(instr->value());
-  LMathRound* result = new(zone()) LMathRound(input);
+  LOperand* input = UseRegister(instr->value());
+  LOperand* temp = FixedTemp(xmm4);
+  LMathRound* result = new(zone()) LMathRound(input, temp);
   return AssignEnvironment(DefineAsRegister(result));
 }
 

src/x64/lithium-x64.h

@@ -835,13 +835,15 @@ class LMathFloor V8_FINAL : public LTemplateInstruction<1, 1, 0> {
 };
 
 
-class LMathRound V8_FINAL : public LTemplateInstruction<1, 1, 0> {
+class LMathRound V8_FINAL : public LTemplateInstruction<1, 1, 1> {
  public:
-  explicit LMathRound(LOperand* value) {
+  explicit LMathRound(LOperand* value, LOperand* temp) {
     inputs_[0] = value;
+    temps_[0] = temp;
   }
 
   LOperand* value() { return inputs_[0]; }
+  LOperand* temp() { return temps_[0]; }
 
   DECLARE_CONCRETE_INSTRUCTION(MathRound, "math-round")
   DECLARE_HYDROGEN_ACCESSOR(UnaryMathOperation)

test/mjsunit/regress/regress-351624.js

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax
+
+var big = 1e10;
+var backup = new Float64Array(1);
+
+function mult0(val){
+  var prod = val * big;
+  backup[0] = prod;
+  var rounded = Math.round(prod);
+  assertEquals(prod, backup[0]);
+  return rounded;
+}
+
+var count = 5;
+for (var i = 0; i < count; i++) {
+  if (i == count - 1) %OptimizeFunctionOnNextCall(mult0);
+  var result = mult0(-1);
+  assertEquals(result, -big);
+}