Revert of [builtins] Introduce proper Float64Exp operator.

src/crankshaft/mips/lithium-codegen-mips.cc

Index: src/crankshaft/mips/lithium-codegen-mips.cc
diff --git a/src/crankshaft/mips/lithium-codegen-mips.cc b/src/crankshaft/mips/lithium-codegen-mips.cc
index 3cee6db394002f1c89328a1a9ca48037fc2b4dec..d351db1c56017c73afe427cc9b99c5fa1122cd1d 100644
--- a/src/crankshaft/mips/lithium-codegen-mips.cc
+++ b/src/crankshaft/mips/lithium-codegen-mips.cc
@@ -3492,10 +3492,16 @@
 
 
 void LCodeGen::DoMathExp(LMathExp* instr) {
-  __ PrepareCallCFunction(0, 1, scratch0());
-  __ MovToFloatParameter(ToDoubleRegister(instr->value()));
-  __ CallCFunction(ExternalReference::ieee754_exp_function(isolate()), 0, 1);
-  __ MovFromFloatResult(ToDoubleRegister(instr->result()));
+  DoubleRegister input = ToDoubleRegister(instr->value());
+  DoubleRegister result = ToDoubleRegister(instr->result());
+  DoubleRegister double_scratch1 = ToDoubleRegister(instr->double_temp());
+  DoubleRegister double_scratch2 = double_scratch0();
+  Register temp1 = ToRegister(instr->temp1());
+  Register temp2 = ToRegister(instr->temp2());
+
+  MathExpGenerator::EmitMathExp(
+      masm(), input, result, double_scratch1, double_scratch2,
+      temp1, temp2, scratch0());
 }