gallium: Add util_blend_factor_uses_dest helper
Drivers may be able to optimize cases where blending is enabled but the
destination colour is not used. This helps detect that case.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6407>
diff --git a/src/gallium/auxiliary/util/u_blend.h b/src/gallium/auxiliary/util/u_blend.h
index d5f9050..7fca2fa 100644
--- a/src/gallium/auxiliary/util/u_blend.h
+++ b/src/gallium/auxiliary/util/u_blend.h
@@ -114,4 +114,22 @@
}
}
+/* To determine if the destination needs to be read while blending */
+
+static inline bool
+util_blend_factor_uses_dest(enum pipe_blendfactor factor, bool alpha)
+{
+ switch (factor) {
+ case PIPE_BLENDFACTOR_DST_ALPHA:
+ case PIPE_BLENDFACTOR_DST_COLOR:
+ case PIPE_BLENDFACTOR_INV_DST_ALPHA:
+ case PIPE_BLENDFACTOR_INV_DST_COLOR:
+ return true;
+ case PIPE_BLENDFACTOR_SRC_ALPHA_SATURATE:
+ return !alpha;
+ default:
+ return false;
+ }
+}
+
#endif /* U_BLEND_H */
