Fix bug in test-code-stubs-x64 which meant not all registers were being checked.

test/cctest/test-code-stubs-x64.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 120 matching lines @@
 #if DEBUG
   // Verify that the tests actually work with the C version. In the release
   // code, the compiler optimizes it away because it's all constant, but does it
   // wrong, triggering an assert on gcc.
   RunAllTruncationTests(&ConvertDToICVersion);
 #endif
 
   Register source_registers[] = {rsp, rax, rbx, rcx, rdx, rsi, rdi, r8, r9};
   Register dest_registers[] = {rax, rbx, rcx, rdx, rsi, rdi, r8, r9};
 
-  for (size_t s = 0; s < sizeof(*source_registers); s++) {
-    for (size_t d = 0; d < sizeof(*dest_registers); d++) {
+  for (size_t s = 0; s < sizeof(source_registers) / sizeof(Register); s++) {
+    for (size_t d = 0; d < sizeof(dest_registers) / sizeof(Register); d++) {
       RunAllTruncationTests(
           MakeConvertDToIFuncTrampoline(isolate,
                                         source_registers[s],
                                         dest_registers[d]));
     }
   }
 }