[Mesa-dev] [PATCH 2/2] blorp: Properly handle Z24X8 blits.

[Jason Ekstrand]

On August 10, 2018 04:18:51 Kenneth Graunke <kenneth at whitecape.org> wrote:

> One of the reasons we didn't notice that R24_UNORM_X8_TYPELESS
> destinations were broken was that an earlier layer was swapping it
> out for B8G8R8A8_UNORM.  That made Z24X8 -> Z24X8 blits work.
>
> However, R32_FLOAT -> R24_UNORM_X8_TYPELESS was still totally broken.
> The old code only considered one format at a time, without thinking
> that format conversion may need to occur.
>
> This patch moves the translation out to a place where it can consider
> both formats.  If both are Z24X8, we continue using B8G8R8A8_UNORM to
> avoid having to do shader math workarounds.  If we have a Z24X8
> destination, but a non-matching source, we use our shader hacks to
> actually render to it properly.

Is the hack even all that useful? It's one more blorp shader compile.  I 
could see scaled depth blits being a thing people care about.  In fact, I 
know they will fairly soon if you catch my drift. :-)  Mind just dropping 
it completely?

--Jason


> ---
> src/intel/blorp/blorp.c      | 12 ------------
> src/intel/blorp/blorp_blit.c | 11 +++++++++++
> 2 files changed, 11 insertions(+), 12 deletions(-)
>
> diff --git a/src/intel/blorp/blorp.c b/src/intel/blorp/blorp.c
> index c36ec703b18..ffe26076e16 100644
> --- a/src/intel/blorp/blorp.c
> +++ b/src/intel/blorp/blorp.c
> @@ -75,18 +75,6 @@ brw_blorp_surface_info_init(struct blorp_context *blorp,
>    if (format == ISL_FORMAT_UNSUPPORTED)
>       format = surf->surf->format;
>
> -   if (format == ISL_FORMAT_R24_UNORM_X8_TYPELESS) {
> -      /* Unfortunately, ISL_FORMAT_R24_UNORM_X8_TYPELESS it isn't supported as
> -       * a render target, which would prevent us from blitting to 24-bit
> -       * depth.  The miptree consists of 32 bits per pixel, arranged as 24-bit
> -       * depth values interleaved with 8 "don't care" bits.  Since depth
> -       * values don't require any blending, it doesn't matter how we interpret
> -       * the bit pattern as long as we copy the right amount of data, so just
> -       * map it as 8-bit BGRA.
> -       */
> -      format = ISL_FORMAT_B8G8R8A8_UNORM;
> -   }
> -
>    info->surf = *surf->surf;
>    info->addr = surf->addr;
>
> diff --git a/src/intel/blorp/blorp_blit.c b/src/intel/blorp/blorp_blit.c
> index 7b49f9afa35..3b84e634bd9 100644
> --- a/src/intel/blorp/blorp_blit.c
> +++ b/src/intel/blorp/blorp_blit.c
> @@ -2241,6 +2241,17 @@ blorp_blit(struct blorp_batch *batch,
>       }
>    }
>
> +   /* ISL_FORMAT_R24_UNORM_X8_TYPELESS it isn't supported as a render target,
> +    * which requires shader math to render to it.  Blitting Z24X8 to Z24X8
> +    * is fairly common though, so we'd like to avoid it.  Since we don't need
> +    * to blend depth values, we can simply pick a renderable format with the
> +    * right number of bits-per-pixel, like 8-bit BGRA.
> +    */
> +   if (dst_surf->surf->format == ISL_FORMAT_R24_UNORM_X8_TYPELESS &&
> +       src_surf->surf->format == ISL_FORMAT_R24_UNORM_X8_TYPELESS) {
> +      src_format = dst_format = ISL_FORMAT_B8G8R8A8_UNORM;
> +   }
> +
>    brw_blorp_surface_info_init(batch->blorp, &params.src, src_surf, src_level,
>                                src_layer, src_format, false);
>    brw_blorp_surface_info_init(batch->blorp, &params.dst, dst_surf, dst_level,
> --
> 2.18.0
>
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