provides a mechanism for optimizing compilers to select the different Register configuration.

src/register-configuration.h

 // Copyright 2014 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.
 
 #ifndef V8_COMPILER_REGISTER_CONFIGURATION_H_
 #define V8_COMPILER_REGISTER_CONFIGURATION_H_
 
 #include "src/base/macros.h"
 
 namespace v8 {
 namespace internal {
 
 // An architecture independent representation of the sets of registers available
 // for instruction creation.
 class RegisterConfiguration {
  public:
+  // Define the optimized compiler selector for register configuration
+  // selection.
+  //
+  // TODO(X87): This distinction in RegisterConfigurations is temporary
+  // until x87 TF supports all of the registers that Crankshaft does.
+  enum CompilerSelector { CRANKSHAFT, TURBOFAN };
+
   // Architecture independent maxes.
   static const int kMaxGeneralRegisters = 32;
   static const int kMaxDoubleRegisters = 32;
 
-  static const RegisterConfiguration* ArchDefault();
+  static const RegisterConfiguration* ArchDefault(CompilerSelector compiler);
 
   RegisterConfiguration(int num_general_registers, int num_double_registers,
                         int num_allocatable_general_registers,
                         int num_allocatable_double_registers,
                         int num_allocatable_aliased_double_registers,
                         const int* allocatable_general_codes,
                         const int* allocatable_double_codes,
                         char const* const* general_names,
                         char const* const* double_names);
 
@@ skipping 47 matching lines @@
   const int* allocatable_general_codes_;
   const int* allocatable_double_codes_;
   char const* const* general_register_names_;
   char const* const* double_register_names_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_REGISTER_CONFIGURATION_H_