[Mesa-stable] [Mesa-dev] [PATCH] nvc0: don't make use of push hint if there are no non-const user vbos

[Samuel Pitoiset]

I don't know if you remember, but I suggested exactly the same patch few 
days ago when I was looking at the Talos issue, but I was not really 
sure if this was the "correct" fix.

Anyways, this patch looks fine to me (even if we don't exactly know why 
it works this way).

This will also improve performance in Talos because the manual push path 
is sometimes slow and that arbitrary limit should be improved.

We still need to fix the remaining issue (ie. the green wall thing) but 
this one is most likely totally unrelated to the push path.

Reviewed-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>

On 06/19/2016 06:34 AM, Ilia Mirkin wrote:
> This makes the check match up what we do on nv50 as well - there's no
> point in switching over the push path if everything's in managed
> buffers. This can happen when a shader uses a vertex without an enabled
> array - we end up passing it a constant attribute.
>
> This also has the effect of "fixing" some flickering in Talos. I have no
> idea why. I've stared at the push logic forwards, backwards, and
> sideways. By always forcing the push path (which is slow), the
> flickering also goes away, but other rendering is still wrong
> (specifically draw 383068 as identified in the bug). However by not
> switching over to the push path, draw 383068 is correct.
>
> Note that other flickering remains in Talos, like the red/green
> walls/floors. This takes care of the shadow flickering though.
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=90513
> Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
> Cc: "12.0" <mesa-stable at lists.freedesktop.org>
> ---
>  src/gallium/drivers/nouveau/nvc0/nvc0_vbo.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/src/gallium/drivers/nouveau/nvc0/nvc0_vbo.c b/src/gallium/drivers/nouveau/nvc0/nvc0_vbo.c
> index 7662bdd..cae621c 100644
> --- a/src/gallium/drivers/nouveau/nvc0/nvc0_vbo.c
> +++ b/src/gallium/drivers/nouveau/nvc0/nvc0_vbo.c
> @@ -441,8 +441,10 @@ nvc0_vertex_arrays_validate(struct nvc0_context *nvc0)
>     if (unlikely(vertex->need_conversion) ||
>         unlikely(nvc0->vertprog->vp.edgeflag < PIPE_MAX_ATTRIBS)) {
>        vbo_mode = 3;
> +   } else if (nvc0->vbo_user & ~nvc0->constant_vbos) {
> +      vbo_mode = nvc0->vbo_push_hint ? 1 : 0;
>     } else {
> -      vbo_mode = (nvc0->vbo_user && nvc0->vbo_push_hint) ? 1 : 0;
> +      vbo_mode = 0;
>     }
>     const_vbos = vbo_mode ? 0 : nvc0->constant_vbos;
>
>