From c65afe541b764a75da68b6bf83aca60d72f88916 Mon Sep 17 00:00:00 2001
From: Icecream95 <ixn@disroot.org>
Date: Fri, 10 Dec 2021 23:51:06 +1300
Subject: [PATCH] pan/mdg: Fix multiple spilt writes in the same bundle

If two instructions in a single bundle both write to a spilt
destination, then we need to reuse the fill and spill instructions,
otherwise the value will be overwritten.

This and the rest of this set of Midgard bug fixes were found from a
vertex shader in Firefox WebRender that is used when a video is
clipped, for example by setting the border-radius CSS property.

CC: mesa-stable
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16382>
---
 src/panfrost/midgard/midgard_ra.c | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/src/panfrost/midgard/midgard_ra.c b/src/panfrost/midgard/midgard_ra.c
index dea96086948..d493f4219e3 100644
--- a/src/panfrost/midgard/midgard_ra.c
+++ b/src/panfrost/midgard/midgard_ra.c
@@ -922,6 +922,11 @@ mir_spill_register(
                 if (is_special_w)
                         spill_slot = spill_index++;
 
+                unsigned last_id = ~0;
+                unsigned last_fill = ~0;
+                unsigned last_spill_index = ~0;
+                midgard_instruction *last_spill = NULL;
+
                 mir_foreach_block(ctx, _block) {
                 midgard_block *block = (midgard_block *) _block;
                 mir_foreach_instr_in_block_safe(block, ins) {
@@ -944,17 +949,19 @@ mir_spill_register(
 
                                 mir_insert_instruction_after_scheduled(ctx, block, ins, st);
                         } else {
-                                unsigned dest = spill_index++;
+                                unsigned bundle = ins->bundle_id;
+                                unsigned dest = (bundle == last_id)? last_spill_index : spill_index++;
 
                                 unsigned bytemask = mir_bytemask(ins);
                                 unsigned write_mask = mir_from_bytemask(mir_round_bytemask_up(
                                                                            bytemask, 32), 32);
 
-                                if (write_count > 1 && bytemask != 0xFFFF) {
+                                if (write_count > 1 && bytemask != 0xFFFF && bundle != last_fill) {
                                         midgard_instruction read =
                                                 v_load_store_scratch(dest, spill_slot, false, 0xF);
                                         mir_insert_instruction_before_scheduled(ctx, block, ins, read);
                                         write_mask = 0xF;
+                                        last_fill = bundle;
                                 }
 
                                 ins->dest = dest;
@@ -966,7 +973,7 @@ mir_spill_register(
                                  * of the spilt instruction need to be direct */
                                 midgard_instruction *it = ins;
                                 while ((it = list_first_entry(&it->link, midgard_instruction, link))
-                                       && (it->bundle_id == ins->bundle_id)) {
+                                       && (it->bundle_id == bundle)) {
 
                                         if (!mir_has_arg(it, spill_node)) continue;
 
@@ -981,9 +988,15 @@ mir_spill_register(
                                 if (move)
                                         dest = spill_index++;
 
-                                midgard_instruction st =
-                                        v_load_store_scratch(dest, spill_slot, true, write_mask);
-                                mir_insert_instruction_after_scheduled(ctx, block, ins, st);
+                                if (last_id == bundle) {
+                                        last_spill->mask |= write_mask;
+                                        u_foreach_bit(c, write_mask)
+                                                last_spill->swizzle[0][c] = c;
+                                } else {
+                                        midgard_instruction st =
+                                                v_load_store_scratch(dest, spill_slot, true, write_mask);
+                                        last_spill = mir_insert_instruction_after_scheduled(ctx, block, ins, st);
+                                }
 
                                 if (move) {
                                         midgard_instruction mv = v_mov(ins->dest, dest);
@@ -991,6 +1004,9 @@ mir_spill_register(
 
                                         mir_insert_instruction_after_scheduled(ctx, block, ins, mv);
                                 }
+
+                                last_id = bundle;
+                                last_spill_index = ins->dest;
                         }
 
                         if (!is_special)