Fixing MathPowHalf on ARM.

src/arm/lithium-codegen-arm.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
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 // 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 3079 matching lines @@
 void LCodeGen::DoMathSqrt(LUnaryMathOperation* instr) {
   DoubleRegister input = ToDoubleRegister(instr->InputAt(0));
   DoubleRegister result = ToDoubleRegister(instr->result());
   __ vsqrt(result, input);
 }
 
 
 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;
+  __ vmov(result, -INFINITY);
+  __ vcmp(input, result);

[Rodolph Perfetta, 2011/12/05 17:38:36]

Confusingly on ARM vcmp does no set the flags! you need a vmrs into pc
afterwards.
There is a macro in the macro-assembler for this:
VPCompareAndSetFlags

+  __ vneg(result, input, eq);
+  __ b(&done, eq);
+
   // Add +0 to convert -0 to +0.
   __ vadd(result, input, kDoubleRegZero);
   __ vsqrt(result, result);
+  __ bind(&done);
 }
 
 
 void LCodeGen::DoPower(LPower* instr) {
   LOperand* left = instr->InputAt(0);
   LOperand* right = instr->InputAt(1);
   Register scratch = scratch0();
   DoubleRegister result_reg = ToDoubleRegister(instr->result());
   Representation exponent_type = instr->hydrogen()->right()->representation();
   if (exponent_type.IsDouble()) {
@@ skipping 1602 matching lines @@
   ASSERT(osr_pc_offset_ == -1);
   osr_pc_offset_ = masm()->pc_offset();
 }
 
 
 
 
 #undef __
 
 } }  // namespace v8::internal