Re-reland: 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 8f40c9052ace2117ba7538d8e73a533ee020d7ec..c7a6cdb4be0e5f94a01c710fa884d2bee9666f4b 100644
--- a/test/cctest/test-code-stubs-arm64.cc
+++ b/test/cctest/test-code-stubs-arm64.cc
@@ -72,11 +72,13 @@ ConvertDToIFunc MakeConvertDToIFuncTrampoline(Isolate* isolate,
   // Save registers make sure they don't get clobbered.
   int source_reg_offset = kDoubleSize;
   int reg_num = 0;
-  for (; reg_num < Register::NumAllocatableRegisters(); ++reg_num) {
+  for (; reg_num < Register::kNumRegisters; ++reg_num) {
     Register reg = Register::from_code(reg_num);
-    if (!reg.is(destination_reg)) {
-      queue.Queue(reg);
-      source_reg_offset += kPointerSize;
+    if (reg.IsAllocatable()) {
+      if (!reg.is(destination_reg)) {
+        queue.Queue(reg);
+        source_reg_offset += kPointerSize;
+      }
     }
   }
   // Re-push the double argument.
@@ -101,10 +103,12 @@ 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.is(destination_reg)) {
-      __ Pop(ip0);
-      __ cmp(reg, ip0);
-      __ Assert(eq, kRegisterWasClobbered);
+    if (reg.IsAllocatable()) {
+      if (!reg.is(destination_reg)) {
+        __ Pop(ip0);
+        __ cmp(reg, ip0);
+        __ Assert(eq, kRegisterWasClobbered);
+      }
     }
   }