Revert of [builtins] Introduce proper Float64Exp operator.

src/crankshaft/mips64/lithium-codegen-mips64.cc

Index: src/crankshaft/mips64/lithium-codegen-mips64.cc
diff --git a/src/crankshaft/mips64/lithium-codegen-mips64.cc b/src/crankshaft/mips64/lithium-codegen-mips64.cc
index 9a0b54037fc1fa8348ea226bf047256a91011db5..c5c93b902945e59e3063d9431f276e92ed24acaf 100644
--- a/src/crankshaft/mips64/lithium-codegen-mips64.cc
+++ b/src/crankshaft/mips64/lithium-codegen-mips64.cc
@@ -3695,10 +3695,16 @@
 
 
 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());
 }