pan/bi: Don't terminate helper threads

Fixes our filtering fails. Roughly equivalent to the .kill texture
bit on Midgard. We'll need to port the dataflow analysis over along with
the .skip analysis, but for now this will suffice.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7081>

diff --git a/src/panfrost/bifrost/bi_pack.c b/src/panfrost/bifrost/bi_pack.c
index f2154c0..e1d0a4a 100644 (file)
--- a/src/panfrost/bifrost/bi_pack.c
+++ b/src/panfrost/bifrost/bi_pack.c
@@ -36,7 +36,7 @@
  * bits on the wire (as well as fixup branches) */
 
 static uint64_t
-bi_pack_header(bi_clause *clause, bi_clause *next_1, bi_clause *next_2, bool is_fragment)
+bi_pack_header(bi_clause *clause, bi_clause *next_1, bi_clause *next_2, bool tdd)
 {
         /* next_dependencies are the union of the dependencies of successors'
          * dependencies */
@@ -48,7 +48,7 @@ bi_pack_header(bi_clause *clause, bi_clause *next_1, bi_clause *next_2, bool is_
                 .flow_control =
                         (next_1 == NULL) ? BIFROST_FLOW_END :
                         clause->flow_control,
-                .terminate_discarded_threads = is_fragment,
+                .terminate_discarded_threads = tdd,
                 .next_clause_prefetch = clause->next_clause_prefetch,
                 .staging_barrier = clause->staging_barrier,
                 .staging_register = clause->staging_register,
@@ -992,20 +992,18 @@ bi_pack_constants(bi_context *ctx, bi_clause *clause,
 static void
 bi_pack_clause(bi_context *ctx, bi_clause *clause,
                 bi_clause *next_1, bi_clause *next_2,
-                struct util_dynarray *emission, gl_shader_stage stage)
+                struct util_dynarray *emission, gl_shader_stage stage,
+                bool tdd)
 {
         struct bi_packed_bundle ins_1 = bi_pack_bundle(clause, clause->bundles[0], clause->bundles[0], true, stage);
         assert(clause->bundle_count == 1);
 
-        /* Used to decide if we elide writes */
-        bool is_fragment = ctx->stage == MESA_SHADER_FRAGMENT;
-
         /* State for packing constants throughout */
         unsigned constant_index = 0;
 
         struct bifrost_fmt1 quad_1 = {
                 .tag = clause->constant_count ? BIFROST_FMT1_CONSTANTS : BIFROST_FMT1_FINAL,
-                .header = bi_pack_header(clause, next_1, next_2, is_fragment),
+                .header = bi_pack_header(clause, next_1, next_2, tdd),
                 .ins_1 = ins_1.lo,
                 .ins_2 = ins_1.hi & ((1 << 11) - 1),
                 .ins_0 = (ins_1.hi >> 11) & 0b111,
@@ -1045,9 +1043,25 @@ bi_next_clause(bi_context *ctx, pan_block *block, bi_clause *clause)
         return NULL;
 }
 
+/* We should terminate discarded threads if there may be discarded threads (a
+ * fragment shader) and helper invocations are not used. Further logic may be
+ * required for future discard/demote differentiation
+ */
+
+static bool
+bi_terminate_discarded_threads(bi_context *ctx)
+{
+        if (ctx->stage == MESA_SHADER_FRAGMENT)
+                return !ctx->nir->info.fs.needs_helper_invocations;
+        else
+                return false;
+}
+
 void
 bi_pack(bi_context *ctx, struct util_dynarray *emission)
 {
+        bool tdd = bi_terminate_discarded_threads(ctx);
+
         util_dynarray_init(emission, NULL);
 
         bi_foreach_block(ctx, _block) {
@@ -1065,7 +1079,7 @@ bi_pack(bi_context *ctx, struct util_dynarray *emission)
                         bi_clause *next = bi_next_clause(ctx, _block, clause);
                         bi_clause *next_2 = is_last ? succ_clause : NULL;
 
-                        bi_pack_clause(ctx, clause, next, next_2, emission, ctx->stage);
+                        bi_pack_clause(ctx, clause, next, next_2, emission, ctx->stage, tdd);
                 }
         }
 }

diff --git a/src/panfrost/bifrost/bifrost.h b/src/panfrost/bifrost/bifrost.h
index 8da1efb..3376022 100644 (file)
--- a/src/panfrost/bifrost/bifrost.h
+++ b/src/panfrost/bifrost/bifrost.h
@@ -134,7 +134,9 @@ struct bifrost_header {
         unsigned zero2 : 1;
 
         /* Terminate discarded threads, rather than continuing execution. Set
-         * for fragment shaders for standard GL behaviour of DISCARD. */
+         * for fragment shaders for standard GL behaviour of DISCARD. Also in a
+         * fragment shader, this disables helper invocations, so cannot be used
+         * in a shader that requires derivatives or texture LOD computation */
         unsigned terminate_discarded_threads : 1;
 
         /* If set, the hardware may prefetch the next clause. If false, the