[v8-dev] MIPS: Fixing MathPowHalf on ARM. (issue 8822014)

[kalmard]

Reviewers: danno, kisg, Paul Lind, Yang,

Message:
Building and testing v8 on mips also requires the following patches to be
landed:
http://codereview.chromium.org/8789012/
http://codereview.chromium.org/8821024/

Description:
MIPS: Fixing MathPowHalf on ARM.

Port r10166 (b57f3f1a), r10167 (202eada9) and r10170 (5c5c96da).

BUG=
TEST=


Please review this at http://codereview.chromium.org/8822014/

Affected files:
  M src/mips/lithium-codegen-mips.cc
  M src/mips/lithium-mips.cc


Index: src/mips/lithium-codegen-mips.cc
diff --git a/src/mips/lithium-codegen-mips.cc  
b/src/mips/lithium-codegen-mips.cc
index  
0af1f50a8e6498de99f5f5d8f0ca735e12a453e5..760ce30c2faeb686821aad25eae347bcc8ea2ba2  
100644
--- a/src/mips/lithium-codegen-mips.cc
+++ b/src/mips/lithium-codegen-mips.cc
@@ -2996,13 +2996,24 @@ void LCodeGen::DoMathSqrt(LUnaryMathOperation*  
instr) {
 void LCodeGen::DoMathPowHalf(LUnaryMathOperation* instr) {
   DoubleRegister input = ToDoubleRegister(instr->InputAt(0));
   DoubleRegister result = ToDoubleRegister(instr->result());
-  DoubleRegister double_scratch = double_scratch0();
+  DoubleRegister temp = ToDoubleRegister(instr->TempAt(0));
+
+  ASSERT(!input.is(result));
+
+  // Note that according to ECMA-262 15.8.2.13:
+  // Math.pow(-Infinity, 0.5) == Infinity
+  // Math.sqrt(-Infinity) == NaN
+  Label done;
+  __ Move(temp, -V8_INFINITY);
+  __ BranchF(USE_DELAY_SLOT, &done, NULL, eq, temp, input);
+  // Set up Infinity in the delay slot.
+  // result is overwritten if the branch is not taken.
+  __ neg_d(result, temp);

   // Add +0 to convert -0 to +0.
-  __ mtc1(zero_reg, double_scratch.low());
-  __ mtc1(zero_reg, double_scratch.high());
-  __ add_d(result, input, double_scratch);
+  __ add_d(result, input, kDoubleRegZero);
   __ sqrt_d(result, result);
+  __ bind(&done);
 }


Index: src/mips/lithium-mips.cc
diff --git a/src/mips/lithium-mips.cc b/src/mips/lithium-mips.cc
index  
19892fccc45f01d24a1a9457217a0f72ef0dca7b..d824deea91935d53cff97a8967f15e6747a176cb  
100644
--- a/src/mips/lithium-mips.cc
+++ b/src/mips/lithium-mips.cc
@@ -1152,6 +1152,13 @@ LInstruction*  
LChunkBuilder::DoUnaryMathOperation(HUnaryMathOperation* instr) {
     LOperand* input = UseFixedDouble(instr->value(), f4);
     LUnaryMathOperation* result = new LUnaryMathOperation(input, NULL);
     return MarkAsCall(DefineFixedDouble(result, f4), instr);
+  } else if (op == kMathPowHalf) {
+    // Input cannot be the same as the result.
+    // See lithium-codegen-mips.cc::DoMathPowHalf.
+    LOperand* input = UseFixedDouble(instr->value(), f8);
+    LOperand* temp = FixedTemp(f6);
+    LUnaryMathOperation* result = new LUnaryMathOperation(input, temp);
+    return DefineFixedDouble(result, f4);
   } else {
     LOperand* input = UseRegisterAtStart(instr->value());
     LOperand* temp = (op == kMathFloor) ? TempRegister() : NULL;
@@ -1165,8 +1172,6 @@ LInstruction*  
LChunkBuilder::DoUnaryMathOperation(HUnaryMathOperation* instr) {
         return DefineAsRegister(result);
       case kMathRound:
         return AssignEnvironment(DefineAsRegister(result));
-      case kMathPowHalf:
-        return DefineAsRegister(result);
       default:
         UNREACHABLE();
         return NULL;


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