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

src/assembler.cc

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // All Rights Reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 // - Redistributions of source code must retain the above copyright notice,
 // this list of conditions and the following disclaimer.
 //
@@ skipping 93 matching lines @@
 
 namespace v8 {
 namespace internal {
 
 // -----------------------------------------------------------------------------
 // Common register code.
 
 const char* Register::ToString() {
   // This is the mapping of allocation indices to registers.
   DCHECK(reg_code >= 0 && reg_code < kNumRegisters);
-  return RegisterConfiguration::ArchDefault()->GetGeneralRegisterName(reg_code);
+  return RegisterConfiguration::ArchDefault(RegisterConfiguration::CRANKSHAFT)
+      ->GetGeneralRegisterName(reg_code);
 }
 
 
 bool Register::IsAllocatable() const {
   return ((1 << reg_code) &
-          RegisterConfiguration::ArchDefault()
+          RegisterConfiguration::ArchDefault(RegisterConfiguration::CRANKSHAFT)
               ->allocatable_general_codes_mask()) != 0;
 }
 
 
 const char* DoubleRegister::ToString() {
   // This is the mapping of allocation indices to registers.
   DCHECK(reg_code >= 0 && reg_code < kMaxNumRegisters);
-  return RegisterConfiguration::ArchDefault()->GetDoubleRegisterName(reg_code);
+  return RegisterConfiguration::ArchDefault(RegisterConfiguration::CRANKSHAFT)
+      ->GetDoubleRegisterName(reg_code);
 }
 
 
 bool DoubleRegister::IsAllocatable() const {
   return ((1 << reg_code) &
-          RegisterConfiguration::ArchDefault()
+          RegisterConfiguration::ArchDefault(RegisterConfiguration::CRANKSHAFT)
               ->allocatable_double_codes_mask()) != 0;
 }
 
 
 // -----------------------------------------------------------------------------
 // Common double constants.
 
 struct DoubleConstant BASE_EMBEDDED {
 double min_int;
 double one_half;
@@ skipping 1745 matching lines @@
 
 
 void Assembler::DataAlign(int m) {
   DCHECK(m >= 2 && base::bits::IsPowerOfTwo32(m));
   while ((pc_offset() & (m - 1)) != 0) {
     db(0);
   }
 }
 }  // namespace internal
 }  // namespace v8