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

src/crankshaft/lithium-allocator.cc

 // Copyright 2012 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/crankshaft/lithium-allocator.h"
 
 #include "src/crankshaft/hydrogen.h"
 #include "src/crankshaft/lithium-inl.h"
 #include "src/crankshaft/lithium-allocator-inl.h"
 #include "src/register-configuration.h"
@@ skipping 1444 matching lines @@
         map->RecordPointer(operand, chunk()->zone());
       }
     }
   }
 }
 
 
 void LAllocator::AllocateGeneralRegisters() {
   LAllocatorPhase phase("L_Allocate general registers", this);
   num_registers_ =
-      RegisterConfiguration::ArchDefault()->num_allocatable_general_registers();
+      RegisterConfiguration::ArchDefault(RegisterConfiguration::CRANKSHAFT)
+          ->num_allocatable_general_registers();
   allocatable_register_codes_ =
-      RegisterConfiguration::ArchDefault()->allocatable_general_codes();
+      RegisterConfiguration::ArchDefault(RegisterConfiguration::CRANKSHAFT)
+          ->allocatable_general_codes();
   mode_ = GENERAL_REGISTERS;
   AllocateRegisters();
 }
 
 
 void LAllocator::AllocateDoubleRegisters() {
   LAllocatorPhase phase("L_Allocate double registers", this);
   num_registers_ =
-      RegisterConfiguration::ArchDefault()->num_allocatable_double_registers();
+      RegisterConfiguration::ArchDefault(RegisterConfiguration::CRANKSHAFT)
+          ->num_allocatable_double_registers();
   allocatable_register_codes_ =
-      RegisterConfiguration::ArchDefault()->allocatable_double_codes();
+      RegisterConfiguration::ArchDefault(RegisterConfiguration::CRANKSHAFT)
+          ->allocatable_double_codes();
   mode_ = DOUBLE_REGISTERS;
   AllocateRegisters();
 }
 
 
 void LAllocator::AllocateRegisters() {
   DCHECK(unhandled_live_ranges_.is_empty());
 
   for (int i = 0; i < live_ranges_.length(); ++i) {
     if (live_ranges_[i] != NULL) {
@@ skipping 696 matching lines @@
   }
 
 #ifdef DEBUG
   if (allocator_ != NULL) allocator_->Verify();
 #endif
 }
 
 
 }  // namespace internal
 }  // namespace v8