Mesa (main): pan/bi: Don't allow spilling coverage mask writes

[GitLab Mirror]

Module: Mesa
Branch: main
Commit: 42a4a123a6f5436537e2689472db8c68da18c5d9
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=42a4a123a6f5436537e2689472db8c68da18c5d9

Author: Alyssa Rosenzweig <alyssa at collabora.com>
Date:   Fri May 27 11:36:01 2022 -0400

pan/bi: Don't allow spilling coverage mask writes

The register precolouring logic assumes that coverage masks are always in R60,
so spilling them causes incorrect results. We could do better. Fixes on Valhall:

   dEQP-GLES3.functional.ubo.random.all_per_block_buffers.28

Fixes: 3df5446cbd4 ("pan/bi: Simplify register precolouring in the IR")
Signed-off-by: Alyssa Rosenzweig <alyssa at collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16748>

---

 src/panfrost/bifrost/bi_ra.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/panfrost/bifrost/bi_ra.c b/src/panfrost/bifrost/bi_ra.c
index 253ac85c789..87f5ab1b35f 100644
--- a/src/panfrost/bifrost/bi_ra.c
+++ b/src/panfrost/bifrost/bi_ra.c
@@ -497,8 +497,21 @@ bi_choose_spill_node(bi_context *ctx, struct lcra_state *l)
                 bi_foreach_dest(ins, d) {
                         unsigned node = bi_get_node(ins->dest[d]);
 
-                        if (node < l->node_count && ins->no_spill)
+                        if (node >= l->node_count)
+                                continue;
+
+                        /* Don't allow spilling coverage mask writes because the
+                         * register preload logic assumes it will stay in R60.
+                         * This could be optimized.
+                         */
+                        if (ins->no_spill ||
+                            ins->op == BI_OPCODE_ATEST ||
+                            ins->op == BI_OPCODE_ZS_EMIT ||
+                            (ins->op == BI_OPCODE_MOV_I32 &&
+                             ins->src[0].type == BI_INDEX_REGISTER &&
+                             ins->src[0].value == 60)) {
                                 BITSET_SET(no_spill, node);
+                        }
                 }
         }