From e84f7bb3b0f213bddf1026d5f48cf07506a4ec26 Mon Sep 17 00:00:00 2001
From: "Yukihiro \"Matz\" Matsumoto" <matz@ruby.or.jp>
Date: Fri, 19 Dec 2025 22:26:36 +0900
Subject: [PATCH] mruby-compiler: remove unnecessary MOVE/APOST in simple masgn

For simple parallel assignment like `a,b = 1,2` without rest or post
variables, skip generating APOST instruction and unnecessary MOVE.
The values are already extracted via AREF.

Before (27 bytes):
    LOADI_1 R3
    LOADI_2 R4
    ARRAY   R3 2
    AREF    R1 R3 0
    AREF    R2 R3 1
    MOVE    R4 R3
    APOST   R4 2 0
    MOVE    R4 R3
    RETURN  R3

After (18 bytes):
    LOADI_1 R3
    LOADI_2 R4
    ARRAY   R3 2
    AREF    R1 R3 0
    AREF    R2 R3 1
    RETURN  R3

Co-authored-by: Claude <noreply@anthropic.com>
---
 mrbgems/mruby-compiler/core/codegen.c | 34 +++++++++++++--------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/mrbgems/mruby-compiler/core/codegen.c b/mrbgems/mruby-compiler/core/codegen.c
index 527e92de9..de52f87af 100644
--- a/mrbgems/mruby-compiler/core/codegen.c
+++ b/mrbgems/mruby-compiler/core/codegen.c
@@ -5086,24 +5086,24 @@ codegen_masgn(codegen_scope *s, node *varnode, node *rhs, int sp, int val)
       }
     }
 
-    gen_move(s, cursp(), rhs_reg, val);
-    push_n(post+1);
-    pop_n(post+1);
-    genop_3(s, OP_APOST, cursp(), n, post);
-    int nn = 1;
-    if (masgn_n->rest && (intptr_t)masgn_n->rest != -1) { /* rest */
-      gen_assignment(s, masgn_n->rest, NULL, cursp(), NOVAL);
-    }
-    if (masgn_n->post) {
-      node *post_part = masgn_n->post;
-      while (post_part) {
-        gen_assignment(s, post_part->car, NULL, cursp()+nn, NOVAL);
-        post_part = post_part->cdr;
-        nn++;
+    /* Only generate APOST if there's rest or post variables */
+    if ((masgn_n->rest && (intptr_t)masgn_n->rest != -1) || masgn_n->post) {
+      gen_move(s, cursp(), rhs_reg, val);
+      push_n(post+1);
+      pop_n(post+1);
+      genop_3(s, OP_APOST, cursp(), n, post);
+      int nn = 1;
+      if (masgn_n->rest && (intptr_t)masgn_n->rest != -1) { /* rest */
+        gen_assignment(s, masgn_n->rest, NULL, cursp(), NOVAL);
+      }
+      if (masgn_n->post) {
+        node *post_part = masgn_n->post;
+        while (post_part) {
+          gen_assignment(s, post_part->car, NULL, cursp()+nn, NOVAL);
+          post_part = post_part->cdr;
+          nn++;
+        }
       }
-    }
-    if (val) {
-      gen_move(s, cursp(), rhs_reg, 0);
     }
 
     if (!val && t) {