Mesa (master): gallium/util: Add helpers to determine if z/s is written

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Module: Mesa
Branch: master
Commit: 7277342b5e8a0a83045621ac77d2c54f9861353f
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=7277342b5e8a0a83045621ac77d2c54f9861353f

Author: Rob Clark <robdclark at chromium.org>
Date:   Wed Jan 20 10:27:55 2021 -0800

gallium/util: Add helpers to determine if z/s is written

For drivers that must control various 'early-z'-like state, it is easy
enough to get this wrong.  So add helpers so we don't have to duplicate
the logic in each driver.

Signed-off-by: Rob Clark <robdclark at chromium.org>
Reviewed-by: Eric Anholt <eric at anholt.net>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig at collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8598>

---

 src/gallium/auxiliary/util/u_inlines.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/src/gallium/auxiliary/util/u_inlines.h b/src/gallium/auxiliary/util/u_inlines.h
index e79e977a441..c5aadc7ca18 100644
--- a/src/gallium/auxiliary/util/u_inlines.h
+++ b/src/gallium/auxiliary/util/u_inlines.h
@@ -763,6 +763,26 @@ util_logicop_reads_dest(enum pipe_logicop op)
    unreachable("bad logicop");
 }
 
+static inline bool
+util_writes_stencil(const struct pipe_stencil_state *s)
+{
+   return s->enabled && s->writemask &&
+        ((s->fail_op != PIPE_STENCIL_OP_KEEP) ||
+         (s->zpass_op != PIPE_STENCIL_OP_KEEP) ||
+         (s->zfail_op != PIPE_STENCIL_OP_KEEP));
+}
+
+static inline bool
+util_writes_depth_stencil(const struct pipe_depth_stencil_alpha_state *zsa)
+{
+   if (zsa->depth_enabled && zsa->depth_writemask &&
+       (zsa->depth_func != PIPE_FUNC_NEVER))
+      return true;
+
+   return util_writes_stencil(&zsa->stencil[0]) ||
+          util_writes_stencil(&zsa->stencil[1]);
+}
+
 static inline struct pipe_context *
 pipe_create_multimedia_context(struct pipe_screen *screen)
 {