From cfde0275e4afe7e48c4f4f9b97f1c85894e47d2f Mon Sep 17 00:00:00 2001
From: Alyssa Rosenzweig <alyssa@collabora.com>
Date: Tue, 22 Mar 2022 22:30:11 -0400
Subject: [PATCH] pan/bi: Model Valhall-style A(CMP)XCHG

Handled consistently with computational atomics.

Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15223>
---
 src/panfrost/bifrost/ISA.xml | 2 ++
 src/panfrost/bifrost/bir.c   | 4 ++--
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/panfrost/bifrost/ISA.xml b/src/panfrost/bifrost/ISA.xml
index d64b4c1..c4a8c94 100644
--- a/src/panfrost/bifrost/ISA.xml
+++ b/src/panfrost/bifrost/ISA.xml
@@ -8253,6 +8253,8 @@
       <opt>aand</opt>
       <opt>aor</opt>
       <opt>axor</opt>
+      <opt>axchg</opt> <!-- For Valhall -->
+      <opt>acmpxchg</opt> <!-- For Valhall -->
     </mod>
     <!-- not actually encoded, but used for IR -->
     <immediate name="sr_count" size="4" pseudo="true"/>
diff --git a/src/panfrost/bifrost/bir.c b/src/panfrost/bifrost/bir.c
index 45b34ba..86e42fa 100644
--- a/src/panfrost/bifrost/bir.c
+++ b/src/panfrost/bifrost/bir.c
@@ -86,9 +86,9 @@ bi_count_staging_registers(const bi_instr *ins)
 unsigned
 bi_count_read_registers(const bi_instr *ins, unsigned s)
 {
-        /* ATOM reads 1 but writes 2 */
+        /* ATOM reads 1 but writes 2. Exception for ACMPXCHG */
         if (s == 0 && ins->op == BI_OPCODE_ATOM_RETURN_I32)
-                return 1;
+                return (ins->atom_opc == BI_ATOM_OPC_ACMPXCHG) ? 2 : 1;
         else if (s == 0 && bi_opcode_props[ins->op].sr_read)
                 return bi_count_staging_registers(ins);
         else if (s == 4 && ins->op == BI_OPCODE_BLEND)
-- 
2.7.4