Mesa (main): pan/bi: Report whether workgroups can be merged

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Module: Mesa
Branch: main
Commit: ccdec68aee284243e722e89830800afb99cf2688
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=ccdec68aee284243e722e89830800afb99cf2688

Author: Alyssa Rosenzweig <alyssa at collabora.com>
Date:   Wed Mar 30 16:31:39 2022 -0400

pan/bi: Report whether workgroups can be merged

This flag gates a Valhall hardware optimization for compute shaders.

Signed-off-by: Alyssa Rosenzweig <alyssa at collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15793>

---

 src/panfrost/bifrost/bifrost_compile.c | 12 ++++++++++++
 src/panfrost/util/pan_ir.h             |  9 +++++++++
 2 files changed, 21 insertions(+)

diff --git a/src/panfrost/bifrost/bifrost_compile.c b/src/panfrost/bifrost/bifrost_compile.c
index 27f7ae6e8d6..bcc8e0c7031 100644
--- a/src/panfrost/bifrost/bifrost_compile.c
+++ b/src/panfrost/bifrost/bifrost_compile.c
@@ -4798,6 +4798,18 @@ bifrost_compile_shader_nir(nir_shader *nir,
                 bi_compile_variant(nir, inputs, binary, sysval_to_id, info, BI_IDVS_NONE);
         }
 
+        if (gl_shader_stage_is_compute(nir->info.stage)) {
+                /* Workgroups may be merged if the structure of the workgroup is
+                 * not software visible. This is true if neither shared memory
+                 * nor barriers are used. The hardware may be able to optimize
+                 * compute shaders that set this flag.
+                 */
+                info->cs.allow_merging_workgroups =
+                        (nir->info.shared_size == 0) &&
+                        !nir->info.uses_control_barrier &&
+                        !nir->info.uses_memory_barrier;
+        }
+
         info->ubo_mask &= (1 << nir->info.num_ubos) - 1;
 
         _mesa_hash_table_u64_destroy(sysval_to_id);
diff --git a/src/panfrost/util/pan_ir.h b/src/panfrost/util/pan_ir.h
index 5b5a0019c94..0ae68b70bf6 100644
--- a/src/panfrost/util/pan_ir.h
+++ b/src/panfrost/util/pan_ir.h
@@ -309,6 +309,15 @@ struct pan_shader_info {
                          */
                         uint64_t secondary_preload;
                 } vs;
+
+                struct {
+                        /* Is it legal to merge workgroups? This is true if the
+                         * shader uses neither barriers nor shared memory.
+                         *
+                         * Used by the Valhall hardware.
+                         */
+                        bool allow_merging_workgroups;
+                } cs;
         };
 
         /* Does the shader contains a barrier? or (for fragment shaders) does it