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

src/crankshaft/lithium-allocator.cc

Index: src/crankshaft/lithium-allocator.cc
diff --git a/src/crankshaft/lithium-allocator.cc b/src/crankshaft/lithium-allocator.cc
index 6c05b57fd8c21f3850c7a5e98411645bfe40da96..5d0529264207b6b7f3c1a7e5b3bf1d5bc2ede29a 100644
--- a/src/crankshaft/lithium-allocator.cc
+++ b/src/crankshaft/lithium-allocator.cc
@@ -1462,9 +1462,11 @@ void LAllocator::PopulatePointerMaps() {
 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();
 }
@@ -1473,9 +1475,11 @@ void LAllocator::AllocateGeneralRegisters() {
 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();
 }