From 231a4774024d6397839b9ee26afde59b328d8636 Mon Sep 17 00:00:00 2001
From: Emma Anholt <emma@anholt.net>
Date: Tue, 13 Jan 2026 17:27:30 -0800
Subject: [PATCH] nir/opcodes: Define udiv_aligned_4 to return poison for
 not-aligned-4.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/39369>
---
 src/compiler/nir/nir_opcodes.py | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/compiler/nir/nir_opcodes.py b/src/compiler/nir/nir_opcodes.py
index cdce76462b4..5a9e2e6a49f 100644
--- a/src/compiler/nir/nir_opcodes.py
+++ b/src/compiler/nir/nir_opcodes.py
@@ -958,8 +958,11 @@ opcode("ushr", 0, tuint, [0, 0], [tuint, tuint32], False, "",
        "src0 >> (src1 & (sizeof(src0) * 8 - 1))",
        description = "Unsigned right-shift." + shift_note)
 
-opcode("udiv_aligned_4", 0, tuint, [0], [tuint], False, "",
-       "src0 >> 2", description = "Divide a multiple of 4 by 4")
+opcode("udiv_aligned_4", 0, tuint, [0], [tuint], False, "", """
+dst = src0 >> 2;
+if (src0 & 3)
+   poison = true;
+""", description = "Divide a multiple of 4 by 4")
 
 opcode("urol", 0, tuint, [0, 0], [tuint, tuint32], False, "", """
    uint32_t rotate_mask = sizeof(src0) * 8 - 1;