Avoid defining DISPATCH_ARCH_DEPEND_WAY macro

when it's not used. This macro is not used when it's direct threaded code.

This patch is purely for readability and has no impact for any behavior.

vm_exec.h

@@ -90,16 +90,6 @@ error !
   LABEL(insn): \
   INSN_ENTRY_SIG(insn); \
 
-/* dispatcher */
-#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__)) && __GNUC__ == 3
-#define DISPATCH_ARCH_DEPEND_WAY(addr) \
-  __asm__ __volatile__("jmp *%0;\t# -- inserted by vm.h\t[length = 2]" : : "r" (addr))
-
-#else
-#define DISPATCH_ARCH_DEPEND_WAY(addr) \
-				/* do nothing */
-#endif
-
 /**********************************/
 #if OPT_DIRECT_THREADED_CODE
 
@@ -112,14 +102,22 @@ error !
 #else
 /* token threaded code */
 
+/* dispatcher */
+#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__)) && __GNUC__ == 3
+#define DISPATCH_ARCH_DEPEND_WAY(addr) \
+  __asm__ __volatile__("jmp *%0;\t# -- inserted by vm.h\t[length = 2]" : : "r" (addr))
+
+#else
+#define DISPATCH_ARCH_DEPEND_WAY(addr) \
+                                /* do nothing */
+#endif
 #define TC_DISPATCH(insn)  \
   DISPATCH_ARCH_DEPEND_WAY(insns_address_table[GET_CURRENT_INSN()]); \
   INSN_DISPATCH_SIG(insn); \
   RB_GNUC_EXTENSION_BLOCK(goto *insns_address_table[GET_CURRENT_INSN()]); \
   rb_bug("tc error");
 
-
-#endif /* DISPATCH_DIRECT_THREADED_CODE */
+#endif /* OPT_DIRECT_THREADED_CODE */
 
 #define END_INSN(insn)      \
   DEBUG_END_INSN();         \