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

test/cctest/test-code-stubs-x87.cc

Index: test/cctest/test-code-stubs-x87.cc
diff --git a/test/cctest/test-code-stubs-x87.cc b/test/cctest/test-code-stubs-x87.cc
index efc39e9a2e2baa77b37331e8e83c7a0dafefa44e..5a420b1a8052ad053bf1870fad23e2256fa12ad1 100644
--- a/test/cctest/test-code-stubs-x87.cc
+++ b/test/cctest/test-code-stubs-x87.cc
@@ -72,8 +72,9 @@ ConvertDToIFunc MakeConvertDToIFuncTrampoline(Isolate* isolate,
   // Save registers make sure they don't get clobbered.
   int reg_num = 0;
   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(esp) && !reg.is(ebp) && !reg.is(destination_reg)) {
         __ push(reg);
         param_offset += kPointerSize;
@@ -92,8 +93,9 @@ ConvertDToIFunc MakeConvertDToIFuncTrampoline(Isolate* isolate,
 
   // Make sure no registers have been unexpectedly clobbered
   for (--reg_num; reg_num >= 0; --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(esp) && !reg.is(ebp) && !reg.is(destination_reg)) {
         __ cmp(reg, MemOperand(esp, 0));
         __ Assert(equal, kRegisterWasClobbered);