radv: Disable NGG culling when conservative overestimation is used.

Even when small primitive culling is disabled, the face culling algorithm
in ac_nir_cull can delete tiny triangles when their area is almost zero.

Cc: mesa-stable
Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20987>
(cherry picked from commit 3508597aa1b88d1b5a6f78ad53d8abcc32cde2c9)

diff --git a/.pick_status.json b/.pick_status.json
index 1f71d51..6483be7 100644 (file)
--- a/.pick_status.json
+++ b/.pick_status.json
@@ -2560,7 +2560,7 @@
         "description": "radv: Disable NGG culling when conservative overestimation is used.",
         "nominated": true,
         "nomination_type": 0,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": null
     },

diff --git a/src/amd/vulkan/radv_cmd_buffer.c b/src/amd/vulkan/radv_cmd_buffer.c
index 4763e5e..3c58427 100644 (file)
--- a/src/amd/vulkan/radv_cmd_buffer.c
+++ b/src/amd/vulkan/radv_cmd_buffer.c
@@ -7510,6 +7510,12 @@ radv_get_ngg_culling_settings(struct radv_cmd_buffer *cmd_buffer, bool vp_y_inve
    const struct radv_graphics_pipeline *pipeline = cmd_buffer->state.graphics_pipeline;
    const struct radv_dynamic_state *d = &cmd_buffer->state.dynamic;
 
+   /* Disable shader culling entirely when conservative overestimate is used.
+    * The face culling algorithm can delete very tiny triangles (even if unintended).
+    */
+   if (d->conservative_rast_mode == VK_CONSERVATIVE_RASTERIZATION_MODE_OVERESTIMATE_EXT)
+      return radv_nggc_none;
+
    /* Cull every triangle when rasterizer discard is enabled. */
    if (d->rasterizer_discard_enable)
       return radv_nggc_front_face | radv_nggc_back_face;
@@ -7531,12 +7537,10 @@ radv_get_ngg_culling_settings(struct radv_cmd_buffer *cmd_buffer, bool vp_y_inve
    if (d->cull_mode & VK_CULL_MODE_BACK_BIT)
       nggc_settings |= radv_nggc_back_face;
 
-   /* Small primitive culling is only valid when conservative overestimation is not used. It's also
-    * disabled for user sample locations because small primitive culling assumes a sample
-    * position at (0.5, 0.5). */
-   bool uses_conservative_overestimate =
-      d->conservative_rast_mode == VK_CONSERVATIVE_RASTERIZATION_MODE_OVERESTIMATE_EXT;
-   if (!uses_conservative_overestimate && !pipeline->uses_user_sample_locations) {
+   /* Small primitive culling assumes a sample position at (0.5, 0.5)
+    * so don't enable it with user sample locations.
+    */
+   if (!pipeline->uses_user_sample_locations) {
       nggc_settings |= radv_nggc_small_primitives;
 
       /* small_prim_precision = num_samples / 2^subpixel_bits