From 316af8c965142c3879f90ed85b6fd92aefa8b322 Mon Sep 17 00:00:00 2001
From: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Date: Mon, 14 Aug 2023 10:41:23 -0400
Subject: [PATCH] nir: Assert the nir_src union is used safely

It is undefined behaviour in C to read a different member of a union than was
written. Nothing in-tree should be using this behaviour with the nir_src union:
nir_if should never be read as nir_instr and vice versa. Assert this.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Acked-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24671>
---
 src/compiler/nir/nir.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index 0c936401458..0597cddcd8e 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -1018,12 +1018,14 @@ nir_src_is_if(const nir_src *src)
 static inline nir_instr *
 nir_src_parent_instr(const nir_src *src)
 {
+   assert(!nir_src_is_if(src));
    return src->renamed_parent_instr;
 }
 
 static inline struct nir_if *
 nir_src_parent_if(const nir_src *src)
 {
+   assert(nir_src_is_if(src));
    return src->parent_if;
 }