Mesa (master): mesa/st: Don't set alpha if ALPHA_TEST is lowered

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Module: Mesa
Branch: master
Commit: c601e730b298c5bdd34bc4335f203d46c5cdf9b3
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=c601e730b298c5bdd34bc4335f203d46c5cdf9b3

Author: Alyssa Rosenzweig <alyssa.rosenzweig at collabora.com>
Date:   Mon Aug 31 07:09:30 2020 -0400

mesa/st: Don't set alpha if ALPHA_TEST is lowered

When PIPE_CAP_ALPHA_TEST is zero, the driver does not support alpha
testing, so alpha shouldn't be set. In particular, alpha.enable should
be zero, since logically alpha testing is not used in the ZSA CSO when
it's lowered in the fragment shader key.

Fixes failing asserts in kicad, rvgl, etc with Panfrost since 6afd4ad.
(We could remove the assert in panfrost instead, but logically setting
alpha.enabled on top of lowering the shader seems wrong?)

As Erik pointed out, this should improve CSO cache behaviour.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig at collabora.com>
Reported-by: Icecream95 <ixn at keemail.me>
Tested-by: Urja Rannikko <urjaman at gmail.com>
Tested-by: Robin Murphy <robin.murphy at arm.com>
Reviewed-by: Erik Faye-Lund <erik.faye-lund at collabora.com>
Fixes: 6afd4addefa ("panfrost: Simplify depth/stencil/alpha")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6523>

---

 src/mesa/state_tracker/st_atom_depth.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/mesa/state_tracker/st_atom_depth.c b/src/mesa/state_tracker/st_atom_depth.c
index 9e12361f881..c6995812e4e 100644
--- a/src/mesa/state_tracker/st_atom_depth.c
+++ b/src/mesa/state_tracker/st_atom_depth.c
@@ -149,7 +149,7 @@ st_update_depth_stencil_alpha(struct st_context *st)
       }
    }
 
-   if (ctx->Color.AlphaEnabled &&
+   if (ctx->Color.AlphaEnabled && !st->lower_alpha_test &&
        !(ctx->DrawBuffer->_IntegerBuffers & 0x1)) {
       dsa->alpha.enabled = 1;
       dsa->alpha.func = st_compare_func_to_pipe(ctx->Color.AlphaFunc);