Revert of [builtins] Introduce proper Float64Exp operator.

src/compiler/x64/code-generator-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.
 
 #include "src/compiler/code-generator.h"
 
 #include "src/ast/scopes.h"
 #include "src/compiler/code-generator-impl.h"
 #include "src/compiler/gap-resolver.h"
 #include "src/compiler/node-matchers.h"
@@ skipping 855 matching lines @@
       }
       __ leaq(i.OutputRegister(), Operand(base, offset.offset()));
       break;
     }
     case kIeee754Float64Atan:
       ASSEMBLE_IEEE754_UNOP(atan);
       break;
     case kIeee754Float64Atan2:
       ASSEMBLE_IEEE754_BINOP(atan2);
       break;
-    case kIeee754Float64Exp:
-      ASSEMBLE_IEEE754_UNOP(exp);
-      break;
     case kIeee754Float64Log:
       ASSEMBLE_IEEE754_UNOP(log);
       break;
     case kIeee754Float64Log1p:
       ASSEMBLE_IEEE754_UNOP(log1p);
       break;
     case kIeee754Float64Log2:
       ASSEMBLE_IEEE754_UNOP(log2);
       break;
     case kIeee754Float64Log10:
@@ skipping 1479 matching lines @@
     int padding_size = last_lazy_deopt_pc_ + space_needed - current_pc;
     __ Nop(padding_size);
   }
 }
 
 #undef __
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8