[RegisterConfiguration] Streamline access to arch defaults, simplify Registers.

test/cctest/test-code-stubs-mips.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Rrdistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Rrdistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Rrdistributions 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 64 matching lines @@
   }
   // Push the double argument.
   __ Subu(sp, sp, Operand(kDoubleSize));
   __ sdc1(f12, MemOperand(sp));
   __ Move(source_reg, sp);
 
   // Save registers make sure they don't get clobbered.
   int source_reg_offset = kDoubleSize;
   int reg_num = 2;
   for (; reg_num < Register::kNumRegisters; ++reg_num) {
-    Register reg = Register::from_code(reg_num);
-    if (reg.IsAllocatable()) {
+    if (RegisterConfiguration::Crankshaft()->IsAllocatableGeneralCode(
+            reg_num)) {
+      Register reg = Register::from_code(reg_num);
       if (!reg.is(destination_reg)) {
         __ push(reg);
         source_reg_offset += kPointerSize;
       }
     }
   }
 
   // Re-push the double argument.
   __ Subu(sp, sp, Operand(kDoubleSize));
   __ sdc1(f12, MemOperand(sp));
 
   // Call through to the actual stub
   if (inline_fastpath) {
     __ ldc1(f12, MemOperand(source_reg));
     __ TryInlineTruncateDoubleToI(destination_reg, f12, &done);
     if (destination_reg.is(source_reg) && !source_reg.is(sp)) {
       // Restore clobbered source_reg.
       __ Addu(source_reg, sp, Operand(source_reg_offset));
     }
   }
   __ Call(start, RelocInfo::EXTERNAL_REFERENCE);
   __ bind(&done);
 
   __ Addu(sp, sp, Operand(kDoubleSize));
 
   // Make sure no registers have been unexpectedly clobbered
   for (--reg_num; reg_num >= 2; --reg_num) {
-    Register reg = Register::from_code(reg_num);
-    if (reg.IsAllocatable()) {
+    if (RegisterConfiguration::Crankshaft()->IsAllocatableGeneralCode(
+            reg_num)) {
+      Register reg = Register::from_code(reg_num);
       if (!reg.is(destination_reg)) {
         __ lw(at, MemOperand(sp, 0));
         __ Assert(eq, kRegisterWasClobbered, reg, Operand(at));
         __ Addu(sp, sp, Operand(kPointerSize));
       }
     }
   }
 
   __ Addu(sp, sp, Operand(kDoubleSize));
 
@@ skipping 68 matching lines @@
                                         false));
       RunAllTruncationTests(
           RunGeneratedCodeCallWrapper,
           MakeConvertDToIFuncTrampoline(isolate,
                                         source_registers[s],
                                         dest_registers[d],
                                         true));
     }
   }
 }