Revert of [builtins] Introduce proper Float64Exp operator.

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

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/crankshaft/x64/lithium-codegen-x64.h"
 
 #include "src/base/bits.h"
 #include "src/code-factory.h"
@@ skipping 3582 matching lines @@
     __ CallStub(&stub);
   } else {
     DCHECK(exponent_type.IsDouble());
     MathPowStub stub(isolate(), MathPowStub::DOUBLE);
     __ CallStub(&stub);
   }
 }
 
 
 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);
 }
 
 
 void LCodeGen::DoMathLog(LMathLog* instr) {
   DCHECK(ToDoubleRegister(instr->value()).is(xmm0));
   DCHECK(ToDoubleRegister(instr->result()).is(xmm0));
   __ PrepareCallCFunction(1);
   __ CallCFunction(ExternalReference::ieee754_log_function(isolate()), 1);
 }
 
@@ skipping 1972 matching lines @@
   __ bind(deferred->exit());
   __ bind(&done);
 }
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64