radeonsi: fix si_num_prims_for_vertices for PIPE_PRIM_POLYGON

Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8548>

diff --git a/src/gallium/drivers/radeonsi/si_state_draw.cpp b/src/gallium/drivers/radeonsi/si_state_draw.cpp
index 26598a1..7f9bdc6 100644 (file)
--- a/src/gallium/drivers/radeonsi/si_state_draw.cpp
+++ b/src/gallium/drivers/radeonsi/si_state_draw.cpp
@@ -341,7 +341,8 @@ static unsigned si_num_prims_for_vertices(enum pipe_prim_type prim,
    case PIPE_PRIM_PATCHES:
       return count / vertices_per_patch;
    case PIPE_PRIM_POLYGON:
-      return count >= 3;
+      /* It's a triangle fan with different edge flags. */
+      return count >= 3 ? count - 2 : 0;
    case SI_PRIM_RECTANGLE_LIST:
       return count / 3;
    default: