From 5935564c3bd0d807327e94f916abf826f5c4bb70 Mon Sep 17 00:00:00 2001
From: Mike Pall <mike>
Date: Sun, 23 Jan 2022 19:13:53 +0100
Subject: [PATCH] Fix FOLD rule for BUFHDR append with intervening buffer use.

Reported by XmiliaH.
---
 src/lj_opt_fold.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/lj_opt_fold.c b/src/lj_opt_fold.c
index 0c5a4a6a..8200b240 100644
--- a/src/lj_opt_fold.c
+++ b/src/lj_opt_fold.c
@@ -598,7 +598,8 @@ LJFOLDF(bufput_bufstr)
     if (fleft->o == IR_BUFHDR && fleft->op2 == IRBUFHDR_RESET &&
 	fleft->prev == hdr &&
 	fleft->op1 == IR(hdr)->op1 &&
-	!(irt_isphi(fright->t) && IR(hdr)->prev)) {
+	!(irt_isphi(fright->t) && IR(hdr)->prev) &&
+	(!LJ_HASBUFFER || J->chain[IR_CALLA] < hdr)) {
       IRRef ref = fins->op1;
       IR(ref)->op2 = IRBUFHDR_APPEND;  /* Modify BUFHDR. */
       IR(ref)->op1 = fright->op1;