X87: [builtins] Introduce proper Float64Exp operator.

src/crankshaft/x87/lithium-x87.cc

Index: src/crankshaft/x87/lithium-x87.cc
diff --git a/src/crankshaft/x87/lithium-x87.cc b/src/crankshaft/x87/lithium-x87.cc
index 06560512777740b88cd2bd99a80523c7a651bc16..dc386ae9ee5a620d947596da90d071f9e6c53716 100644
--- a/src/crankshaft/x87/lithium-x87.cc
+++ b/src/crankshaft/x87/lithium-x87.cc
@@ -1177,11 +1177,8 @@ LInstruction* LChunkBuilder::DoMathClz32(HUnaryMathOperation* instr) {
 LInstruction* LChunkBuilder::DoMathExp(HUnaryMathOperation* instr) {
   DCHECK(instr->representation().IsDouble());
   DCHECK(instr->value()->representation().IsDouble());
-  LOperand* value = UseRegisterAtStart(instr->value());
-  LOperand* temp1 = FixedTemp(ecx);
-  LOperand* temp2 = FixedTemp(edx);
-  LMathExp* result = new(zone()) LMathExp(value, temp1, temp2);
-  return MarkAsCall(DefineSameAsFirst(result), instr);
+  LOperand* input = UseRegisterAtStart(instr->value());
+  return MarkAsCall(DefineSameAsFirst(new (zone()) LMathExp(input)), instr);
 }