commit 3d51c27de5576b9a62761726f33b0cc7a66da1d2
author Juan A. Suarez Romero <jasuarez@igalia.com> Wed Oct 21 11:45:08 2020 +0200
committer Marge Bot <eric+marge@anholt.net> Wed Oct 21 16:33:43 2020 +0000
tree 27ec947e0eb7c8162f23ca1d2241e990a2d813cf
parent 33ccf0e9bc5cdfbc9b2bd821c7a31d48043a8cf8

st/mesa: initialize lower alpha func to ALWAYS

The lower_alpha_func is initialized as COMPARE_FUNC_NEVER, and the
nir_lower_alpha_test() only executed if the alpha_func has changed.

This means when user runs an alpha test with GL_NEVER function the
lowering is never executed, and no fragment is discarded.

Rather, we would like to initialize the function as COMPARE_FUNC_ALWAYS,
and run the lowering when the alpha_func is different. If user runs the
alpha test with GL_ALWAYS, indeed the lowering is never executed; but
using GL_ALWAYS makes no fragment is discarded, so it is like not
executing the testing.

Signed-off-by: Juan A. Suarez Romero <jasuarez@igalia.com>
Reviewed-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7251>

src/mesa/state_tracker/st_atom_shader.c

diff --git a/src/mesa/state_tracker/st_atom_shader.c b/src/mesa/state_tracker/st_atom_shader.c
index d92a542..18acc30 100644
--- a/src/mesa/state_tracker/st_atom_shader.c
+++ b/src/mesa/state_tracker/st_atom_shader.c
@@ -125,7 +125,7 @@
                             st->ctx->Light.ShadeModel == GL_FLAT;
 
       /* _NEW_COLOR */
-      key.lower_alpha_func = COMPARE_FUNC_NEVER;
+      key.lower_alpha_func = COMPARE_FUNC_ALWAYS;
       if (st->lower_alpha_test && _mesa_is_alpha_test_enabled(st->ctx))
          key.lower_alpha_func = st->ctx->Color.AlphaFunc;
 

src/mesa/state_tracker/st_cb_bitmap.c

diff --git a/src/mesa/state_tracker/st_cb_bitmap.c b/src/mesa/state_tracker/st_cb_bitmap.c
index fcdf26e..11976da 100644
--- a/src/mesa/state_tracker/st_cb_bitmap.c
+++ b/src/mesa/state_tracker/st_cb_bitmap.c
@@ -179,6 +179,7 @@
    key.bitmap = GL_TRUE;
    key.clamp_color = st->clamp_frag_color_in_shader &&
                      ctx->Color._ClampFragmentColor;
+   key.lower_alpha_func = COMPARE_FUNC_ALWAYS;
 
    fpv = st_get_fp_variant(st, st->fp, &key);
 

src/mesa/state_tracker/st_cb_drawpixels.c

diff --git a/src/mesa/state_tracker/st_cb_drawpixels.c b/src/mesa/state_tracker/st_cb_drawpixels.c
index 0fad2fb..4b8242c 100644
--- a/src/mesa/state_tracker/st_cb_drawpixels.c
+++ b/src/mesa/state_tracker/st_cb_drawpixels.c
@@ -1148,6 +1148,7 @@
    key.pixelMaps = ctx->Pixel.MapColorFlag;
    key.clamp_color = st->clamp_frag_color_in_shader &&
                      ctx->Color._ClampFragmentColor;
+   key.lower_alpha_func = COMPARE_FUNC_ALWAYS;
 
    fpv = st_get_fp_variant(st, st->fp, &key);
 
@@ -1177,6 +1178,7 @@
    key.pixelMaps = 0;
    key.clamp_color = st->clamp_frag_color_in_shader &&
                      ctx->Color._ClampFragmentColor;
+   key.lower_alpha_func = COMPARE_FUNC_ALWAYS;
 
    fpv = st_get_fp_variant(st, st->fp, &key);
 

src/mesa/state_tracker/st_program.c

diff --git a/src/mesa/state_tracker/st_program.c b/src/mesa/state_tracker/st_program.c
index 2f9bba8..c6a96c8 100644
--- a/src/mesa/state_tracker/st_program.c
+++ b/src/mesa/state_tracker/st_program.c
@@ -1247,7 +1247,7 @@
          finalize = true;
       }
 
-      if (key->lower_alpha_func != COMPARE_FUNC_NEVER) {
+      if (key->lower_alpha_func != COMPARE_FUNC_ALWAYS) {
          _mesa_add_state_reference(params, alpha_ref_state);
          NIR_PASS_V(state.ir.nir, nir_lower_alpha_test, key->lower_alpha_func,
                     false, alpha_ref_state);
@@ -1943,6 +1943,7 @@
       memset(&key, 0, sizeof(key));
 
       key.st = st->has_shareable_shaders ? NULL : st;
+      key.lower_alpha_func = COMPARE_FUNC_ALWAYS;
       st_get_fp_variant(st, p, &key);
       break;
    }