From 79fd6ae01b4191cba21a3cdb7ebe3d0248d38f18 Mon Sep 17 00:00:00 2001
From: Georg Lehmann <dadschoorse@gmail.com>
Date: Wed, 28 Feb 2024 17:34:59 +0100
Subject: [PATCH] aco/post-ra: assume scc is going to be overwritten by phis at
 end of blocks
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Cc: mesa-stable
Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27855>
(cherry picked from commit bd93e8372d0fdcbdfba66faf7d037b08a5efa473)
---
 .pick_status.json                         | 2 +-
 src/amd/compiler/aco_optimizer_postRA.cpp | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/.pick_status.json b/.pick_status.json
index 874a33c09c1..09e28145b86 100644
--- a/.pick_status.json
+++ b/.pick_status.json
@@ -984,7 +984,7 @@
         "description": "aco/post-ra: assume scc is going to be overwritten by phis at end of blocks",
         "nominated": true,
         "nomination_type": 0,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": null,
         "notes": null
diff --git a/src/amd/compiler/aco_optimizer_postRA.cpp b/src/amd/compiler/aco_optimizer_postRA.cpp
index 5ae59dad2ce..e56c36e0cce 100644
--- a/src/amd/compiler/aco_optimizer_postRA.cpp
+++ b/src/amd/compiler/aco_optimizer_postRA.cpp
@@ -748,6 +748,12 @@ optimize_postRA(Program* program)
 
       for (aco_ptr<Instruction>& instr : block.instructions)
          process_instruction(ctx, instr);
+
+      /* SCC might get overwritten by copies or swaps from parallelcopies
+       * inserted by SSA-elimination for linear phis.
+       */
+      if (!block.scc_live_out)
+         ctx.instr_idx_by_regs[block.index][scc] = overwritten_unknown_instr;
    }
 
    /* Cleanup pass