Revert of [builtins] Introduce proper Float64Exp operator.

src/crankshaft/x64/lithium-codegen-x64.cc

Index: src/crankshaft/x64/lithium-codegen-x64.cc
diff --git a/src/crankshaft/x64/lithium-codegen-x64.cc b/src/crankshaft/x64/lithium-codegen-x64.cc
index 236157a24ca7bcb28ea0fcd2d9a3ef71296757f3..0a2a0b687c02719dddfe28148f3cec4e2c40e00b 100644
--- a/src/crankshaft/x64/lithium-codegen-x64.cc
+++ b/src/crankshaft/x64/lithium-codegen-x64.cc
@@ -3600,10 +3600,13 @@
 
 
 void LCodeGen::DoMathExp(LMathExp* instr) {
-  DCHECK(ToDoubleRegister(instr->value()).is(xmm0));
-  DCHECK(ToDoubleRegister(instr->result()).is(xmm0));
-  __ PrepareCallCFunction(1);
-  __ CallCFunction(ExternalReference::ieee754_exp_function(isolate()), 1);
+  XMMRegister input = ToDoubleRegister(instr->value());
+  XMMRegister result = ToDoubleRegister(instr->result());
+  XMMRegister temp0 = double_scratch0();
+  Register temp1 = ToRegister(instr->temp1());
+  Register temp2 = ToRegister(instr->temp2());
+
+  MathExpGenerator::EmitMathExp(masm(), input, result, temp0, temp1, temp2);
 }