PPC/s390: [builtins] Introduce proper Float64Exp operator.

src/s390/codegen-s390.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 //
 // Copyright IBM Corp. 2012, 2015. All rights reserved.
 //
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_S390_CODEGEN_S390_H_
 #define V8_S390_CODEGEN_S390_H_
 
 #include "src/ast/ast.h"
 #include "src/macro-assembler.h"
 
 namespace v8 {
 namespace internal {
 
 class StringCharLoadGenerator : public AllStatic {
  public:
   // Generates the code for handling different string types and loading the
   // indexed character into |result|.  We expect |index| as untagged input and
   // |result| as untagged output.
   static void Generate(MacroAssembler* masm, Register string, Register index,
                        Register result, Label* call_runtime);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(StringCharLoadGenerator);
 };
-
-class MathExpGenerator : public AllStatic {
- public:
-  // Register input isn't modified. All other registers are clobbered.
-  static void EmitMathExp(MacroAssembler* masm, DoubleRegister input,
-                          DoubleRegister result, DoubleRegister double_scratch1,
-                          DoubleRegister double_scratch2, Register temp1,
-                          Register temp2, Register temp3);
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(MathExpGenerator);
-};
-
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_S390_CODEGEN_S390_H_