[Mesa-dev] [PATCH] i965: Fix predicated-send-based discards with MRT.

[Tapani Pälli]

On 03/05/2014 03:20 AM, Eric Anholt wrote:
> We need the header setup to not be predicated on which pixels are
> undiscarded.  I'm not sure originally if I had thought that the mask
> disable implied predicate disable, or if I had just misread the mask
> disable as predicate disable.  Either way, I know I had spent more time
> thinking about this in the gen8 generator than the gen7 generator.
>
> Plus, it turns out that I had mis-implemented the "the GPU will use the
> predicate unless this header is present" comment, by skipping setting up
> the pixel mask when the header was present.
>
> Fixes GPU hangs in piglit glsl-fs-discard-mrt, Trine, Trine 2 and
> preusmably MLL.
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=75207
> ---
>   src/mesa/drivers/dri/i965/brw_fs_generator.cpp | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
> index 748a2e2..e590bdf 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
> @@ -103,14 +103,14 @@ fs_generator::generate_fb_write(fs_inst *inst)
>       */
>      brw_push_insn_state(p);
>      brw_set_mask_control(p, BRW_MASK_DISABLE);
> +   brw_set_predicate_control(p, BRW_PREDICATE_NONE);
>      brw_set_compression_control(p, BRW_COMPRESSION_NONE);
>   
>      if (inst->header_present) {
>         /* On HSW, the GPU will use the predicate on SENDC, unless the header is
>          * present.
>          */
> -      if (!brw->is_haswell && ((fp && fp->UsesKill) ||
> -                               c->key.alpha_test_func)) {
> +      if ((fp && fp->UsesKill) || c->key.alpha_test_func) {
>            struct brw_reg pixel_mask;
>   
>            if (brw->gen >= 6)

Yep just tested and GPU hangs with Metro LL get fixed with this patch.

Tested-by: Tapani Pälli <tapani.palli at intel.com>

// Tapani