Fixing MathPowHalf on ARM.

BUG=v8:397
TEST=regress-397.js

Review URL: http://codereview.chromium.org/8800009

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10166 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/lithium-codegen-arm.cc

@@ -3097,9 +3097,19 @@ void LCodeGen::DoMathSqrt(LUnaryMathOperation* instr) {
 void LCodeGen::DoMathPowHalf(LUnaryMathOperation* instr) {
   DoubleRegister input = ToDoubleRegister(instr->InputAt(0));
   DoubleRegister result = ToDoubleRegister(instr->result());
+
+  // Note that according to ECMA-262 15.8.2.13:
+  // Math.pow(-Infinity, 0.5) == Infinity
+  // Math.sqrt(-Infinity) == NaN
+  Label done;
+  __ VFPCompareAndSetFlags(input, -V8_INFINITY);
+  __ vneg(result, input, eq);
+  __ b(&done, eq);
+
   // Add +0 to convert -0 to +0.
   __ vadd(result, input, kDoubleRegZero);
   __ vsqrt(result, result);
+  __ bind(&done);
 }
 
 

test/mjsunit/math-pow.js

@@ -135,6 +135,11 @@ function test() {
   assertEquals(+Infinity, Math.pow(-0, -0.6));
   assertEquals(-Infinity, Math.pow(-0, -1));
   assertEquals(-Infinity, Math.pow(-0, -10000000001));
+  
+  assertEquals(4, Math.pow(16, 0.5));
+  assertEquals(NaN, Math.pow(-16, 0.5));
+  assertEquals(0.25, Math.pow(16, -0.5));
+  assertEquals(NaN, Math.pow(-16, -0.5));
 
   // Tests from Sputnik S8.5_A13_T1.
   assertTrue(