Mesa (main): radeonsi: fix issues with draw-level splitting for the prim discard CS

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Module: Mesa
Branch: main
Commit: 81365c86f95caa6bc966bf7b1e6884c83a73a148
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=81365c86f95caa6bc966bf7b1e6884c83a73a148

Author: Marek Olšák <marek.olsak at amd.com>
Date:   Mon May 31 21:58:37 2021 -0400

radeonsi: fix issues with draw-level splitting for the prim discard CS

- move the unreachable statement up by inlining u_decomposed_prims_for_vertices
- the last draw was not submitted after splitting
- move "count" to the non-multi draw path

Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer at amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11510>

---

 .../drivers/radeonsi/si_compute_prim_discard.c       | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/src/gallium/drivers/radeonsi/si_compute_prim_discard.c b/src/gallium/drivers/radeonsi/si_compute_prim_discard.c
index d2040b24f6a..ae043037ba0 100644
--- a/src/gallium/drivers/radeonsi/si_compute_prim_discard.c
+++ b/src/gallium/drivers/radeonsi/si_compute_prim_discard.c
@@ -577,9 +577,16 @@ si_prepare_prim_discard_or_split_draw(struct si_context *sctx, const struct pipe
 
    struct radeon_cmdbuf *gfx_cs = &sctx->gfx_cs;
    unsigned prim = info->mode;
-   unsigned count = total_count;
    unsigned instance_count = info->instance_count;
-   unsigned num_prims_per_instance = u_decomposed_prims_for_vertices(prim, count);
+
+   unsigned num_prims_per_instance;
+   if (prim == PIPE_PRIM_TRIANGLES)
+      num_prims_per_instance = total_count / 3;
+   else if (prim == PIPE_PRIM_TRIANGLE_STRIP)
+      num_prims_per_instance = total_count - 2; /* approximation ignoring multi draws */
+   else
+      unreachable("shouldn't get here");
+
    unsigned num_prims = num_prims_per_instance * instance_count;
    unsigned out_indexbuf_size = num_prims * 12;
    bool ring_full = !si_check_ring_space(sctx, out_indexbuf_size);
@@ -597,8 +604,6 @@ si_prepare_prim_discard_or_split_draw(struct si_context *sctx, const struct pipe
          vert_count_per_subdraw = PRIMS_PER_BATCH * 3;
       else if (prim == PIPE_PRIM_TRIANGLE_STRIP)
          vert_count_per_subdraw = PRIMS_PER_BATCH;
-      else
-         unreachable("shouldn't get here");
 
       /* Split multi draws first. */
       if (num_draws > 1) {
@@ -628,6 +633,12 @@ si_prepare_prim_discard_or_split_draw(struct si_context *sctx, const struct pipe
             count += draws[i].count;
             num_draws_split++;
          }
+
+         if (count) {
+            /* Submit the remaining draws.  */
+            assert(num_draws_split > 0);
+            sctx->b.draw_vbo(&sctx->b, info, drawid_offset, NULL, draws + first_draw, num_draws_split);
+         }
          return SI_PRIM_DISCARD_MULTI_DRAW_SPLIT;
       }
 
@@ -635,6 +646,7 @@ si_prepare_prim_discard_or_split_draw(struct si_context *sctx, const struct pipe
       struct pipe_draw_info split_draw = *info;
       struct pipe_draw_start_count_bias split_draw_range = draws[0];
       unsigned base_start = split_draw_range.start;
+      unsigned count = draws[0].count;
 
       if (prim == PIPE_PRIM_TRIANGLES) {
          assert(vert_count_per_subdraw < count);