Thanks to Sergey Kaplun. #1430
#if LJ_GC64
#define LJ_ALLOC_MBITS 47 /* 128 TB in LJ_GC64 mode. */
-#elif LJ_TARGET_X64 && LJ_HASJIT
-/* Due to limitations in the x64 compiler backend. */
+#elif LJ_TARGET_X64
+/* Due to limitations in the x64 non-GC64 VM. */
#define LJ_ALLOC_MBITS 31 /* 2 GB on x64 with !LJ_GC64. */
#else
#define LJ_ALLOC_MBITS 32 /* 4 GB on other archs with !LJ_GC64. */