From acb223497d84c65139a7eaaac395b42f112249ac Mon Sep 17 00:00:00 2001
From: Mike Pall <mike>
Date: Tue, 7 Jul 2026 11:07:19 +0200
Subject: x64/ARM64/MIPS64: Fix constant bit shift code generation.

Reported by Sergey Kaplun. #1480
---
 src/lj_asm_arm64.h | 3 ++-
 src/lj_asm_mips.h  | 3 ++-
 src/lj_asm_x86.h   | 5 +++--
 3 files changed, 7 insertions(+), 4 deletions(-)

(limited to 'src')

diff --git a/src/lj_asm_arm64.h b/src/lj_asm_arm64.h
index dfc5490fa..d068b153a 100644
--- a/src/lj_asm_arm64.h
+++ b/src/lj_asm_arm64.h
@@ -1549,7 +1549,8 @@ static void asm_bitshift(ASMState *as, IRIns *ir, A64Ins ai, A64Shift sh)
   int32_t shmask = irt_is64(ir->t) ? 63 : 31;
   if (irref_isk(ir->op2)) {  /* Constant shifts. */
     Reg left, dest = ra_dest(as, ir, RSET_GPR);
-    int32_t shift = (IR(ir->op2)->i & shmask);
+    IRIns *irr = IR(ir->op2);
+    int32_t shift = ((irr->o == IR_KINT ? irr->i : (int32_t)ir_kint64(irr)->u64) & shmask);
     IRIns *irl = IR(ir->op1);
     if (shmask == 63) ai += A64I_UBFMx - A64I_UBFMw;
 
diff --git a/src/lj_asm_mips.h b/src/lj_asm_mips.h
index a54af233f..7565f442e 100644
--- a/src/lj_asm_mips.h
+++ b/src/lj_asm_mips.h
@@ -2089,7 +2089,8 @@ static void asm_bitshift(ASMState *as, IRIns *ir, MIPSIns mi, MIPSIns mik)
 {
   Reg dest = ra_dest(as, ir, RSET_GPR);
   if (irref_isk(ir->op2)) {  /* Constant shifts. */
-    uint32_t shift = (uint32_t)IR(ir->op2)->i;
+    IRIns *irr = IR(ir->op2);
+    uint32_t shift = (uint32_t)(LJ_32 || irr->o == IR_KINT) ? (uint32_t)irr->i : (uint32_t)ir_kint64(irr)->u64;
     if (LJ_64 && irt_is64(ir->t)) mik |= (shift & 32) ? MIPSI_D32 : MIPSI_D;
     emit_dta(as, mik, dest, ra_hintalloc(as, ir->op1, dest, RSET_GPR),
 	     (shift & 31));
diff --git a/src/lj_asm_x86.h b/src/lj_asm_x86.h
index 3d68baefd..943cf2b77 100644
--- a/src/lj_asm_x86.h
+++ b/src/lj_asm_x86.h
@@ -2318,9 +2318,10 @@ static void asm_bitshift(ASMState *as, IRIns *ir, x86Shift xs, x86Op xv)
   IRIns *irr = IR(rref);
   Reg dest;
   if (irref_isk(rref)) {  /* Constant shifts. */
-    int shift;
+    int32_t shift;
     dest = ra_dest(as, ir, RSET_GPR);
-    shift = irr->i & (irt_is64(ir->t) ? 63 : 31);
+    shift = (LJ_32 || irr->o == IR_KINT) ? irr->i : (int32_t)ir_kint64(irr)->u64;
+    shift &= (irt_is64(ir->t) ? 63 : 31);
     if (!xv && shift && (as->flags & JIT_F_BMI2)) {
       Reg left = asm_fuseloadm(as, ir->op1, RSET_GPR, irt_is64(ir->t));
       if (left != dest) {  /* BMI2 rotate right by constant. */
-- 
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