Refactor rb_vm_insn_addr2insn calls

It's been a way too much amount of ifdefs.

compile.c

@@ -1383,11 +1383,7 @@ update_catch_except_flags(struct rb_iseq_constant_body *body)
        BREAK/NEXT/REDO catch table entries are used only when `throw` insn is used in the block. */
     pos = 0;
     while (pos < body->iseq_size) {
-#if OPT_DIRECT_THREADED_CODE || OPT_CALL_THREADED_CODE
-        insn = rb_vm_insn_addr2insn((void *)body->iseq_encoded[pos]);
-#else
-        insn = (int)body->iseq_encoded[pos];
-#endif
+        insn = rb_vm_insn_decode(body->iseq_encoded[pos]);
         if (insn == BIN(throw)) {
             set_catch_except_p(body);
             break;

internal/compile.h

@@ -23,6 +23,7 @@ VALUE rb_insns_name_array(void);
 
 /* iseq.c */
 int rb_vm_insn_addr2insn(const void *);
+int rb_vm_insn_decode(const VALUE encoded);
 
 MJIT_SYMBOL_EXPORT_BEGIN
 /* iseq.c (export) */

iseq.c

@@ -3192,6 +3192,18 @@ rb_vm_insn_addr2insn(const void *addr)
     rb_bug("rb_vm_insn_addr2insn: invalid insn address: %p", addr);
 }
 
+// Decode `iseq->body->iseq_encoded[i]` to an insn.
+int
+rb_vm_insn_decode(const VALUE encoded)
+{
+#if OPT_DIRECT_THREADED_CODE || OPT_CALL_THREADED_CODE
+    int insn = rb_vm_insn_addr2insn((void *)encoded);
+#else
+    int insn = (int)encoded;
+#endif
+    return insn;
+}
+
 static inline int
 encoded_iseq_trace_instrument(VALUE *iseq_encoded_insn, rb_event_flag_t turnon, bool remain_current_trace)
 {

mjit_compile.c

@@ -222,18 +222,13 @@ static void
 compile_insns(FILE *f, const struct rb_iseq_constant_body *body, unsigned int stack_size,
               unsigned int pos, struct compile_status *status)
 {
-    int insn;
     struct compile_branch branch;
 
     branch.stack_size = stack_size;
     branch.finish_p = false;
 
     while (pos < body->iseq_size && !ALREADY_COMPILED_P(status, pos) && !branch.finish_p) {
-#if OPT_DIRECT_THREADED_CODE || OPT_CALL_THREADED_CODE
-        insn = rb_vm_insn_addr2insn((void *)body->iseq_encoded[pos]);
-#else
-        insn = (int)body->iseq_encoded[pos];
-#endif
+        int insn = rb_vm_insn_decode(body->iseq_encoded[pos]);
         status->stack_size_for_pos[pos] = (int)branch.stack_size;
 
         fprintf(f, "\nlabel_%d: /* %s */\n", pos, insn_name(insn));
@@ -406,11 +401,7 @@ inlinable_iseq_p(const struct rb_iseq_constant_body *body)
 
     unsigned int pos = 0;
     while (pos < body->iseq_size) {
-#if OPT_DIRECT_THREADED_CODE || OPT_CALL_THREADED_CODE
-        int insn = rb_vm_insn_addr2insn((void *)body->iseq_encoded[pos]);
-#else
-        int insn = (int)body->iseq_encoded[pos];
-#endif
+        int insn = rb_vm_insn_decode(body->iseq_encoded[pos]);
         // All insns in the ISeq except `leave` (to be overridden in the inlined code)
         // should meet following strong assumptions:
         //   * Do not require `cfp->sp` motion
@@ -468,11 +459,7 @@ init_ivar_compile_status(const struct rb_iseq_constant_body *body, struct compil
     status->ivar_serial = 0;
 
     while (pos < body->iseq_size) {
-#if OPT_DIRECT_THREADED_CODE || OPT_CALL_THREADED_CODE
-        int insn = rb_vm_insn_addr2insn((void *)body->iseq_encoded[pos]);
-#else
-        int insn = (int)body->iseq_encoded[pos];
-#endif
+        int insn = rb_vm_insn_decode(body->iseq_encoded[pos]);
         if (insn == BIN(getinstancevariable) || insn == BIN(setinstancevariable)) {
             IVC ic = (IVC)body->iseq_encoded[pos+2];
             IVC ic_copy = &(status->is_entries + ((union iseq_inline_storage_entry *)ic - body->is_entries))->iv_cache;
@@ -527,11 +514,7 @@ precompile_inlinable_iseqs(FILE *f, const rb_iseq_t *iseq, struct compile_status
     const struct rb_iseq_constant_body *body = iseq->body;
     unsigned int pos = 0;
     while (pos < body->iseq_size) {
-#if OPT_DIRECT_THREADED_CODE || OPT_CALL_THREADED_CODE
-        int insn = rb_vm_insn_addr2insn((void *)body->iseq_encoded[pos]);
-#else
-        int insn = (int)body->iseq_encoded[pos];
-#endif
+        int insn = rb_vm_insn_decode(body->iseq_encoded[pos]);
         if (insn == BIN(opt_send_without_block)) { // `compile_inlined_cancel_handler` supports only `opt_send_without_block`
             CALL_DATA cd = (CALL_DATA)body->iseq_encoded[pos + 1];
             const struct rb_callinfo *ci = cd->ci;

mjit_worker.c

@@ -734,11 +734,7 @@ set_compiling_iseqs(const rb_iseq_t *iseq)
 
     unsigned int pos = 0;
     while (pos < iseq->body->iseq_size) {
-#if OPT_DIRECT_THREADED_CODE || OPT_CALL_THREADED_CODE
-        int insn = rb_vm_insn_addr2insn((void *)iseq->body->iseq_encoded[pos]);
-#else
-        int insn = (int)iseq->body->iseq_encoded[pos];
-#endif
+        int insn = rb_vm_insn_decode(iseq->body->iseq_encoded[pos]);
         if (insn == BIN(opt_send_without_block)) {
             CALL_DATA cd = (CALL_DATA)iseq->body->iseq_encoded[pos + 1];
             extern const rb_iseq_t *rb_mjit_inlinable_iseq(const struct rb_callinfo *ci, const struct rb_callcache *cc);