freedreno/a6xx: more early-z

Technically we only have to do late-z in the alpha-test or discard case
if depth-write is enabled.  If depth write is disabled, the depth read /
test / conditional-write interlock that we need to emulate is not a
problem, so we can still use early-z test.

There is a slightly weird case when there is no zsbuf attachment (see
dEQP-GLES31.functional.fbo.no_attachments.*) where the hw wants us to
use LATE_Z.. not entirely sure if this is an interaction with occlusion
query or just a pecularity of how the hw works when there is no depth
buffer.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5336>

diff --git a/src/gallium/drivers/freedreno/a6xx/fd6_emit.c b/src/gallium/drivers/freedreno/a6xx/fd6_emit.c
index a805872638fee550fed03134d35b1c672168524a..0853a9529b04f916b55b04af2cc5f010455324dd 100644 (file)
--- a/src/gallium/drivers/freedreno/a6xx/fd6_emit.c
+++ b/src/gallium/drivers/freedreno/a6xx/fd6_emit.c
@@ -584,12 +584,21 @@ build_vbo_state(struct fd6_emit *emit)
 static enum a6xx_ztest_mode
 compute_ztest_mode(struct fd6_emit *emit, bool lrz_valid)
 {
-       struct fd6_zsa_stateobj *zsa = fd6_zsa_stateobj(emit->ctx->zsa);
+       struct fd_context *ctx =  emit->ctx;
+       struct pipe_framebuffer_state *pfb = &ctx->batch->framebuffer;
+       struct fd6_zsa_stateobj *zsa = fd6_zsa_stateobj(ctx->zsa);
        const struct ir3_shader_variant *fs = emit->fs;
 
        if (fs->no_earlyz || fs->writes_pos) {
                return A6XX_LATE_Z;
-       } else if (fs->has_kill || zsa->alpha_test) {
+       } else if ((fs->has_kill || zsa->alpha_test) &&
+                       (zsa->base.depth.writemask || !pfb->zsbuf)) {
+               /* Slightly odd, but seems like the hw wants us to select
+                * LATE_Z mode if there is no depth buffer + discard.  Either
+                * that, or when occlusion query is enabled.  See:
+                *
+                * dEQP-GLES31.functional.fbo.no_attachments.*
+                */
                return lrz_valid ? A6XX_EARLY_LRZ_LATE_Z : A6XX_LATE_Z;
        } else {
                return A6XX_EARLY_Z;