A64: Use a scope utility to allocate scratch registers.

test/cctest/test-utils-a64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 305 matching lines @@
   } else {
     UNREACHABLE();
   }
 }
 
 
 void RegisterDump::Dump(MacroAssembler* masm) {
   ASSERT(__ StackPointer().Is(csp));
 
   // Ensure that we don't unintentionally clobber any registers.
-  Register old_tmp0 = __ Tmp0();
-  Register old_tmp1 = __ Tmp1();
-  FPRegister old_fptmp0 = __ FPTmp0();
-  __ SetScratchRegisters(NoReg, NoReg);
-  __ SetFPScratchRegister(NoFPReg);
+  UseScratchRegisterScope temps(masm);
+  temps.ExcludeAll();
 
   // Preserve some temporary registers.
   Register dump_base = x0;
   Register dump = x1;
   Register tmp = x2;
   Register dump_base_w = dump_base.W();
   Register dump_w = dump.W();
   Register tmp_w = tmp.W();
 
   // Offsets into the dump_ structure.
@@ skipping 70 matching lines @@
 
   __ Add(dump2, dump2_base, x_offset);
   __ Str(dump_base, MemOperand(dump2, dump_base.code() * kXRegSizeInBytes));
   __ Str(dump, MemOperand(dump2, dump.code() * kXRegSizeInBytes));
   __ Str(tmp, MemOperand(dump2, tmp.code() * kXRegSizeInBytes));
 
   // Finally, restore dump2_base and dump2.
   __ Ldr(dump2_base, MemOperand(dump2, dump2_base.code() * kXRegSizeInBytes));
   __ Ldr(dump2, MemOperand(dump2, dump2.code() * kXRegSizeInBytes));
 
-  // Restore the MacroAssembler's scratch registers.
-  __ SetScratchRegisters(old_tmp0, old_tmp1);
-  __ SetFPScratchRegister(old_fptmp0);
-
   completed_ = true;
 }