zink: fix flat shading on filled quads

Quads emulated by zink will now have the correct provoking vertex.

Also outputs of the previous shader stage that would normally
not be passed down to the FS (when no GS is bound) will now be skipped.

Different provoking vertex modes are not handled yet.

Acked-by: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Reviewed-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21238>

diff --git a/src/gallium/drivers/zink/zink_compiler.c b/src/gallium/drivers/zink/zink_compiler.c
index e869c10..a2afd76 100644 (file)
--- a/src/gallium/drivers/zink/zink_compiler.c
+++ b/src/gallium/drivers/zink/zink_compiler.c
@@ -913,7 +913,7 @@ zink_create_quads_emulation_gs(const nir_shader_compiler_options *options,
    nir->info.gs.input_primitive = SHADER_PRIM_LINES_ADJACENCY;
    nir->info.gs.output_primitive = SHADER_PRIM_TRIANGLE_STRIP;
    nir->info.gs.vertices_in = 4;
-   nir->info.gs.vertices_out = 4;
+   nir->info.gs.vertices_out = 6;
    nir->info.gs.invocations = 1;
    nir->info.gs.active_stream_mask = 1;
 
@@ -959,9 +959,10 @@ zink_create_quads_emulation_gs(const nir_shader_compiler_options *options,
       out_vars[num_vars++] = out;
    }
 
-   for (unsigned i = 0; i < 4; ++i) {
+   int mapping[] = {0, 1, 2, 0, 2, 3};
+   for (unsigned i = 0; i < 6; ++i) {
       /* swap indices 2 and 3 */
-      int idx = i == 2 ? 3 : (i == 3 ? 2 : i);
+      int idx = mapping[i];
       /* Copy inputs to outputs. */
       for (unsigned j = 0; j < num_vars; ++j) {
          if (in_vars[j]->data.location == VARYING_SLOT_EDGE) {
@@ -973,6 +974,8 @@ zink_create_quads_emulation_gs(const nir_shader_compiler_options *options,
                        (1u << value->num_components) - 1);
       }
       nir_emit_vertex(&b, 0);
+      if (i == 2)
+        nir_end_primitive(&b, 0);
    }
 
    nir_end_primitive(&b, 0);