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

src/ppc/macro-assembler-ppc.cc

 // 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.
 
 #include <assert.h>  // For assert
 #include <limits.h>  // For LONG_MIN, LONG_MAX.
 
 #if V8_TARGET_ARCH_PPC
 
 #include "src/base/bits.h"
@@ skipping 608 matching lines @@
 }
 
 
 MemOperand MacroAssembler::SafepointRegisterSlot(Register reg) {
   return MemOperand(sp, SafepointRegisterStackIndex(reg.code()) * kPointerSize);
 }
 
 
 MemOperand MacroAssembler::SafepointRegistersAndDoublesSlot(Register reg) {
   // General purpose registers are pushed last on the stack.
-  const RegisterConfiguration* config = RegisterConfiguration::ArchDefault();
+  const RegisterConfiguration* config =
+      RegisterConfiguration::ArchDefault(RegisterConfiguration::CRANKSHAFT);
   int doubles_size = config->num_allocatable_double_registers() * kDoubleSize;
   int register_offset = SafepointRegisterStackIndex(reg.code()) * kPointerSize;
   return MemOperand(sp, doubles_size + register_offset);
 }
 
 
 void MacroAssembler::CanonicalizeNaN(const DoubleRegister dst,
                                      const DoubleRegister src) {
   // Turn potential sNaN into qNaN.
   fsub(dst, src, kDoubleRegZero);
@@ skipping 3607 matching lines @@
                                    Register reg4, Register reg5,
                                    Register reg6) {
   RegList regs = 0;
   if (reg1.is_valid()) regs |= reg1.bit();
   if (reg2.is_valid()) regs |= reg2.bit();
   if (reg3.is_valid()) regs |= reg3.bit();
   if (reg4.is_valid()) regs |= reg4.bit();
   if (reg5.is_valid()) regs |= reg5.bit();
   if (reg6.is_valid()) regs |= reg6.bit();
 
-  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);
     Register candidate = Register::from_code(code);
     if (regs & candidate.bit()) continue;
     return candidate;
   }
   UNREACHABLE();
   return no_reg;
 }
 
@@ skipping 120 matching lines @@
   }
   if (mag.shift > 0) srawi(result, result, mag.shift);
   ExtractBit(r0, dividend, 31);
   add(result, result, r0);
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_PPC