Allow the optimizing code generator to call Math.pow with untagged doubles.

src/ia32/lithium-ia32.cc

Index: src/ia32/lithium-ia32.cc
===================================================================
--- src/ia32/lithium-ia32.cc	(revision 5948)
+++ src/ia32/lithium-ia32.cc	(working copy)
@@ -1366,6 +1366,8 @@
       return AssignEnvironment(DefineAsRegister(result));
     case kMathSqrt:
       return DefineSameAsFirst(result);
+    case kMathPowHalf:
+      return AssignEnvironment(DefineSameAsFirst(result));
     default:
       UNREACHABLE();
       return NULL;
@@ -1566,6 +1568,22 @@
 }
 
 
+LInstruction* LChunkBuilder::DoPower(HPower* instr) {
+  ASSERT(instr->representation().IsDouble());
+  // We call a C function for double power. It can't trigger a GC.
+  // We need to use fixed result register for the call.
+  Representation exponent_type = instr->right()->representation();
+  ASSERT(instr->left()->representation().IsDouble());
+  LOperand* left = UseFixedDouble(instr->left(), xmm1);
+  LOperand* right = exponent_type.IsDouble() ?
+      UseFixedDouble(instr->right(), xmm2) :
+      UseFixed(instr->right(), eax);
+  LPower* result = new LPower(left, right);
+  return MarkAsCall(DefineFixedDouble(result, xmm1), instr,
+                    CAN_DEOPTIMIZE_EAGERLY);
+}
+
+
 LInstruction* LChunkBuilder::DoCompare(HCompare* instr) {
   Token::Value op = instr->token();
   if (instr->left()->representation().IsInteger32()) {