Revert of [builtins] Introduce proper Float64Exp operator.

src/crankshaft/mips64/lithium-mips64.cc

Index: src/crankshaft/mips64/lithium-mips64.cc
diff --git a/src/crankshaft/mips64/lithium-mips64.cc b/src/crankshaft/mips64/lithium-mips64.cc
index f001ee487af9fe743034631bf1af49514d18c6a7..17f59d84fccff7dfc499b963435e33416a0bc452 100644
--- a/src/crankshaft/mips64/lithium-mips64.cc
+++ b/src/crankshaft/mips64/lithium-mips64.cc
@@ -1107,8 +1107,12 @@
 LInstruction* LChunkBuilder::DoMathExp(HUnaryMathOperation* instr) {
   DCHECK(instr->representation().IsDouble());
   DCHECK(instr->value()->representation().IsDouble());
-  LOperand* input = UseFixedDouble(instr->value(), f4);
-  return MarkAsCall(DefineFixedDouble(new (zone()) LMathExp(input), f4), instr);
+  LOperand* input = UseRegister(instr->value());
+  LOperand* temp1 = TempRegister();
+  LOperand* temp2 = TempRegister();
+  LOperand* double_temp = TempDoubleRegister();
+  LMathExp* result = new(zone()) LMathExp(input, double_temp, temp1, temp2);
+  return DefineAsRegister(result);
 }