Revert of Remove register index/code indirection

test/cctest/test-code-stubs-arm64.cc

Index: test/cctest/test-code-stubs-arm64.cc
diff --git a/test/cctest/test-code-stubs-arm64.cc b/test/cctest/test-code-stubs-arm64.cc
index c7a6cdb4be0e5f94a01c710fa884d2bee9666f4b..ecb8819345378667c3ae774954c4185c07e600e4 100644
--- a/test/cctest/test-code-stubs-arm64.cc
+++ b/test/cctest/test-code-stubs-arm64.cc
@@ -72,13 +72,11 @@
   // Save registers make sure they don't get clobbered.
   int source_reg_offset = kDoubleSize;
   int reg_num = 0;
-  for (; reg_num < Register::kNumRegisters; ++reg_num) {
+  for (;reg_num < Register::NumAllocatableRegisters(); ++reg_num) {
     Register reg = Register::from_code(reg_num);
-    if (reg.IsAllocatable()) {
-      if (!reg.is(destination_reg)) {
-        queue.Queue(reg);
-        source_reg_offset += kPointerSize;
-      }
+    if (!reg.is(destination_reg)) {
+      queue.Queue(reg);
+      source_reg_offset += kPointerSize;
     }
   }
   // Re-push the double argument.
@@ -103,12 +101,10 @@
   // // 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 (!reg.is(destination_reg)) {
-        __ Pop(ip0);
-        __ cmp(reg, ip0);
-        __ Assert(eq, kRegisterWasClobbered);
-      }
+    if (!reg.is(destination_reg)) {
+      __ Pop(ip0);
+      __ cmp(reg, ip0);
+      __ Assert(eq, kRegisterWasClobbered);
     }
   }