MIPS: Fixing MathPowHalf on ARM.

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

BUG=
TEST=

Review URL: http://codereview.chromium.org/8822014
Patch from Daniel Kalmar <kalmard@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10214 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/lithium-codegen-mips.cc

@@ -3002,13 +3002,24 @@ 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);
 }
 
 

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;