From 44da356e97a159f5962f32a526525d14bcd13179 Mon Sep 17 00:00:00 2001
From: Mike Pall <mike>
Date: Sat, 9 Sep 2023 18:16:31 +0200
Subject: [PATCH] ARM: Fix stack check code generation.

Thanks to Peter Cawley. #1068
---
 src/lj_asm_arm.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/lj_asm_arm.h b/src/lj_asm_arm.h
index 20e57393..f53f708b 100644
--- a/src/lj_asm_arm.h
+++ b/src/lj_asm_arm.h
@@ -1947,6 +1947,7 @@ static void asm_hiop(ASMState *as, IRIns *ir)
 static void asm_stack_check(ASMState *as, BCReg topslot,
 			    IRIns *irp, RegSet allow, ExitNo exitno)
 {
+  int savereg = 0;
   Reg pbase;
   uint32_t k;
   if (irp) {
@@ -1957,12 +1958,14 @@ static void asm_stack_check(ASMState *as, BCReg topslot,
       pbase = rset_pickbot(allow);
     } else {
       pbase = RID_RET;
-      emit_lso(as, ARMI_LDR, RID_RET, RID_SP, 0);  /* Restore temp. register. */
+      savereg = 1;
     }
   } else {
     pbase = RID_BASE;
   }
   emit_branch(as, ARMF_CC(ARMI_BL, CC_LS), exitstub_addr(as->J, exitno));
+  if (savereg)
+    emit_lso(as, ARMI_LDR, RID_RET, RID_SP, 0);  /* Restore temp. register. */
   k = emit_isk12(0, (int32_t)(8*topslot));
   lua_assert(k);
   emit_n(as, ARMI_CMP^k, RID_TMP);
@@ -1974,7 +1977,7 @@ static void asm_stack_check(ASMState *as, BCReg topslot,
     if (ra_hasspill(irp->s))
       emit_lso(as, ARMI_LDR, pbase, RID_SP, sps_scale(irp->s));
     emit_lso(as, ARMI_LDR, RID_TMP, RID_TMP, (i & 4095));
-    if (ra_hasspill(irp->s) && !allow)
+    if (savereg)
       emit_lso(as, ARMI_STR, RID_RET, RID_SP, 0);  /* Save temp. register. */
     emit_loadi(as, RID_TMP, (i & ~4095));
   } else {