[Mesa-dev] [PATCH] st/mesa: Only enable depth writes if the function isn't EQUAL.

[Kenneth Graunke]

If the depth function is EQUAL, then we'll only write the depth value
when it already matches what's in the buffer, which is pointless.
Skipping these writes can save bandwidth.

The state tracker can easily take care of this, so all drivers benefit.
---
 src/mesa/state_tracker/st_atom_depth.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Not well tested, sorry.

diff --git a/src/mesa/state_tracker/st_atom_depth.c b/src/mesa/state_tracker/st_atom_depth.c
index 6ddb8f525cf..9e12361f881 100644
--- a/src/mesa/state_tracker/st_atom_depth.c
+++ b/src/mesa/state_tracker/st_atom_depth.c
@@ -107,8 +107,9 @@ st_update_depth_stencil_alpha(struct st_context *st)
    if (ctx->DrawBuffer->Visual.depthBits > 0) {
       if (ctx->Depth.Test) {
          dsa->depth.enabled = 1;
-         dsa->depth.writemask = ctx->Depth.Mask;
          dsa->depth.func = st_compare_func_to_pipe(ctx->Depth.Func);
+         if (dsa->depth.func != PIPE_FUNC_EQUAL)
+            dsa->depth.writemask = ctx->Depth.Mask;
       }
       if (ctx->Depth.BoundsTest) {
          dsa->depth.bounds_test = 1;
-- 
2.18.0