Revert of [builtins] Introduce proper Float64Exp operator.

src/crankshaft/mips/lithium-mips.cc

Index: src/crankshaft/mips/lithium-mips.cc
diff --git a/src/crankshaft/mips/lithium-mips.cc b/src/crankshaft/mips/lithium-mips.cc
index ea14026d9a46ace973cf79d74fe157b90c90ca75..7b481db188042e26cbb38efdd6eacb5fa1659b2d 100644
--- a/src/crankshaft/mips/lithium-mips.cc
+++ b/src/crankshaft/mips/lithium-mips.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);
 }