From 724a2e26387b3a5f34939fa24a6eb16b218ebf73 Mon Sep 17 00:00:00 2001
From: "Yukihiro \"Matz\" Matsumoto" <matz@ruby.or.jp>
Date: Mon, 19 Jan 2026 14:15:28 +0900
Subject: [PATCH] vm: add OP_RETSELF instruction for returning self

Fuse LOADSELF + RETURN sequence into single RETSELF instruction.
Saves 2 bytes per occurrence (3 bytes -> 1 byte).

Found 25 occurrences in mrblib, saving 50 bytes total.

Co-authored-by: Claude <noreply@anthropic.com>
---
 include/mruby/ops.h                   | 1 +
 mrbgems/mruby-compiler/core/codegen.c | 7 ++++++-
 src/codedump.c                        | 3 +++
 src/vm.c                              | 4 ++++
 4 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/include/mruby/ops.h b/include/mruby/ops.h
index f8b91728b..9602dc51b 100644
--- a/include/mruby/ops.h
+++ b/include/mruby/ops.h
@@ -71,6 +71,7 @@ OPCODE(KEYEND,     Z)        /* raise unless kdict.empty? */
 OPCODE(KARG,       BB)       /* R[a] = kdict[Syms[b]]; kdict.delete(Syms[b]) */
 OPCODE(RETURN,     B)        /* return R[a] (normal) */
 OPCODE(RETURN_BLK, B)        /* return R[a] (in-block return) */
+OPCODE(RETSELF,    Z)        /* return self */
 OPCODE(BREAK,      B)        /* break R[a] */
 OPCODE(BLKPUSH,    BS)       /* R[a] = block (16=m5:r1:m5:d1:lv4) */
 OPCODE(ADD,        B)        /* R[a] = R[a]+R[a+1] */
diff --git a/mrbgems/mruby-compiler/core/codegen.c b/mrbgems/mruby-compiler/core/codegen.c
index 36a60b1d1..9a0c2d257 100644
--- a/mrbgems/mruby-compiler/core/codegen.c
+++ b/mrbgems/mruby-compiler/core/codegen.c
@@ -1141,7 +1141,12 @@ gen_return(codegen_scope *s, uint8_t op, uint16_t src)
       rewind_pc(s);
       genop_1(s, op, data.b);
     }
-    else if (data.insn != OP_RETURN) {
+    else if (data.insn == OP_LOADSELF && src == data.a && op == OP_RETURN) {
+      /* LOADSELF + RETURN -> RETSELF */
+      rewind_pc(s);
+      genop_0(s, OP_RETSELF);
+    }
+    else if (data.insn != OP_RETURN && data.insn != OP_RETSELF) {
       genop_1(s, op, src);
     }
   }
diff --git a/src/codedump.c b/src/codedump.c
index 2bc3c9110..58962c83d 100644
--- a/src/codedump.c
+++ b/src/codedump.c
@@ -390,6 +390,9 @@ codedump(mrb_state *mrb, const mrb_irep *irep, FILE *out)
       fprintf(out, "RETURN_BLK\tR%d\t", a);
       print_lv_a(mrb, irep, a, out);
       break;
+    CASE(OP_RETSELF, Z):
+      fprintf(out, "RETSELF\n");
+      break;
     CASE(OP_BREAK, B):
       fprintf(out, "BREAK\t\tR%d\t", a);
       print_lv_a(mrb, irep, a, out);
diff --git a/src/vm.c b/src/vm.c
index 21d5d3907..5568ff54b 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -2661,6 +2661,10 @@ RETRY_TRY_BLOCK:
       RAISE_LIT(mrb, E_LOCALJUMP_ERROR, "unexpected return");
       /* not reached */
     }
+    CASE(OP_RETSELF, Z) {
+      a = 0;
+      goto NORMAL_RETURN;
+    }
     CASE(OP_RETURN, B) {
       mrb_int acc;
       mrb_value v;