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

src/crankshaft/ia32/lithium-gap-resolver-ia32.cc

 // Copyright 2011 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.
 
 #if V8_TARGET_ARCH_IA32
 
 #include "src/crankshaft/ia32/lithium-codegen-ia32.h"
 #include "src/crankshaft/ia32/lithium-gap-resolver-ia32.h"
 #include "src/register-configuration.h"
 
@@ skipping 149 matching lines @@
     if (!moves_[i].IsEliminated() && moves_[i].source()->Equals(operand)) {
       ++count;
     }
   }
   return count;
 }
 
 
 Register LGapResolver::GetFreeRegisterNot(Register reg) {
   int skip_index = reg.is(no_reg) ? -1 : reg.code();
-  const RegisterConfiguration* config = RegisterConfiguration::ArchDefault();
+  const RegisterConfiguration* config =
+      RegisterConfiguration::ArchDefault(RegisterConfiguration::CRANKSHAFT);
   for (int i = 0; i < config->num_allocatable_general_registers(); ++i) {
     int code = config->GetAllocatableGeneralCode(i);
     if (source_uses_[code] == 0 && destination_uses_[code] > 0 &&
         code != skip_index) {
       return Register::from_code(code);
     }
   }
   return no_reg;
 }
 
 
 bool LGapResolver::HasBeenReset() {
   if (!moves_.is_empty()) return false;
   if (spilled_register_ >= 0) return false;
-  const RegisterConfiguration* config = RegisterConfiguration::ArchDefault();
+  const RegisterConfiguration* config =
+      RegisterConfiguration::ArchDefault(RegisterConfiguration::CRANKSHAFT);
   for (int i = 0; i < config->num_allocatable_general_registers(); ++i) {
     int code = config->GetAllocatableGeneralCode(i);
     if (source_uses_[code] != 0) return false;
     if (destination_uses_[code] != 0) return false;
   }
   return true;
 }
 
 
 void LGapResolver::Verify() {
@@ skipping 33 matching lines @@
   if (spilled_register_ >= 0) {
     return Register::from_code(spilled_register_);
   }
 
   // 2. We may have a free register that we can use without spilling.
   Register free = GetFreeRegisterNot(no_reg);
   if (!free.is(no_reg)) return free;
 
   // 3. Prefer to spill a register that is not used in any remaining move
   // because it will not need to be restored until the end.
-  const RegisterConfiguration* config = RegisterConfiguration::ArchDefault();
+  const RegisterConfiguration* config =
+      RegisterConfiguration::ArchDefault(RegisterConfiguration::CRANKSHAFT);
   for (int i = 0; i < config->num_allocatable_general_registers(); ++i) {
     int code = config->GetAllocatableGeneralCode(i);
     if (source_uses_[code] == 0 && destination_uses_[code] == 0) {
       Register scratch = Register::from_code(code);
       __ push(scratch);
       spilled_register_ = code;
       return scratch;
     }
   }
 
@@ skipping 229 matching lines @@
     source_uses_[destination->index()] = CountSourceUses(destination);
   }
 }
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_IA32