Revert of [builtins] Introduce proper Float64Exp operator.

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

Index: src/crankshaft/arm/lithium-codegen-arm.cc
diff --git a/src/crankshaft/arm/lithium-codegen-arm.cc b/src/crankshaft/arm/lithium-codegen-arm.cc
index 65ad7107e1c8b81daacab29e49a748bef8cf26c2..8eda5922f428547bfe55c7e7c5f11c07447bf94e 100644
--- a/src/crankshaft/arm/lithium-codegen-arm.cc
+++ b/src/crankshaft/arm/lithium-codegen-arm.cc
@@ -3540,10 +3540,16 @@
 
 
 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()));
+  DwVfpRegister input = ToDoubleRegister(instr->value());
+  DwVfpRegister result = ToDoubleRegister(instr->result());
+  DwVfpRegister double_scratch1 = ToDoubleRegister(instr->double_temp());
+  DwVfpRegister 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());
 }