zink: clear null image surfaces to 0

GL Spec says that imageLoad from incomplete images must return 0.
This is not really spec compliant as for proper behavior nullDescriptor
and robustImageAccess2 is needed.
A workaround for lack of either of these requires a shader variant.
Clearing the null surface and hoping the app doesn't write to the image
is closer to spec, while avoiding a shader recompile.

KHR-GL46.shader_image_load_store.incomplete_textures tests this.

cc: mesa-stable

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21135>
(cherry picked from commit 22e91af1a77361249b9c71ee609b67ec187e612c)

diff --git a/.pick_status.json b/.pick_status.json
index 6127275..1b818c5 100644 (file)
--- a/.pick_status.json
+++ b/.pick_status.json
@@ -1174,7 +1174,7 @@
         "description": "zink: clear null image surfaces to 0",
         "nominated": true,
         "nomination_type": 0,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": null
     },

diff --git a/src/gallium/drivers/zink/zink_context.c b/src/gallium/drivers/zink/zink_context.c
index 3360ae9..ba11566 100644 (file)
--- a/src/gallium/drivers/zink/zink_context.c
+++ b/src/gallium/drivers/zink/zink_context.c
@@ -4685,6 +4685,13 @@ zink_get_dummy_pipe_surface(struct zink_context *ctx, int samples_index)
 {
    if (!ctx->dummy_surface[samples_index]) {
       ctx->dummy_surface[samples_index] = zink_surface_create_null(ctx, PIPE_TEXTURE_2D, 1024, 1024, BITFIELD_BIT(samples_index));
+      /* This is possibly used with imageLoad which according to GL spec must return 0 */
+      if (!samples_index) {
+         union pipe_color_union color = {0};
+         struct pipe_box box;
+         u_box_2d(0, 0, 1024, 1024, &box);
+         ctx->base.clear_texture(&ctx->base, ctx->dummy_surface[samples_index]->texture, 0, &box, &color);
+      }
    }
    return ctx->dummy_surface[samples_index];
 }