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

src/x64/macro-assembler-x64.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.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/base/bits.h"
 #include "src/base/division-by-constant.h"
 #include "src/bootstrapper.h"
 #include "src/codegen.h"
@@ skipping 4024 matching lines @@
 #ifdef _WIN64
   const int kShadowSpace = 4;
   arg_stack_space += kShadowSpace;
 #endif
   // Optionally save all XMM registers.
   if (save_doubles) {
     int space = XMMRegister::kMaxNumRegisters * kDoubleSize +
                 arg_stack_space * kRegisterSize;
     subp(rsp, Immediate(space));
     int offset = -2 * kPointerSize;
-    const RegisterConfiguration* config = RegisterConfiguration::ArchDefault();
+    const RegisterConfiguration* config =
+        RegisterConfiguration::ArchDefault(RegisterConfiguration::CRANKSHAFT);
     for (int i = 0; i < config->num_allocatable_double_registers(); ++i) {
       DoubleRegister reg =
           DoubleRegister::from_code(config->GetAllocatableDoubleCode(i));
       Movsd(Operand(rbp, offset - ((i + 1) * kDoubleSize)), reg);
     }
   } else if (arg_stack_space > 0) {
     subp(rsp, Immediate(arg_stack_space * kRegisterSize));
   }
 
   // Get the required frame alignment for the OS.
@@ skipping 25 matching lines @@
   EnterExitFramePrologue(false);
   EnterExitFrameEpilogue(arg_stack_space, false);
 }
 
 
 void MacroAssembler::LeaveExitFrame(bool save_doubles, bool pop_arguments) {
   // Registers:
   // r15 : argv
   if (save_doubles) {
     int offset = -2 * kPointerSize;
-    const RegisterConfiguration* config = RegisterConfiguration::ArchDefault();
+    const RegisterConfiguration* config =
+        RegisterConfiguration::ArchDefault(RegisterConfiguration::CRANKSHAFT);
     for (int i = 0; i < config->num_allocatable_double_registers(); ++i) {
       DoubleRegister reg =
           DoubleRegister::from_code(config->GetAllocatableDoubleCode(i));
       Movsd(reg, Operand(rbp, offset - ((i + 1) * kDoubleSize)));
     }
   }
 
   if (pop_arguments) {
     // Get the return address from the stack and restore the frame pointer.
     movp(rcx, Operand(rbp, kFPOnStackSize));
@@ skipping 1225 matching lines @@
   movl(rax, dividend);
   shrl(rax, Immediate(31));
   addl(rdx, rax);
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64