On 07/06/2012 03:29 PM, Paul Berry wrote:
> This patch updates the blorp engine to properly handle the case where
> the surface being textured from uses Gen7's CMS MSAA layout. The
> following changes were necessary:
>
> - Before reading color values from the surface, we need to read from
> the MCS buffer using the ld_mcs sampler message. This is done by
> the mcs_fetch() function, and the result is stored in the mcs_data
> register. This only needs to be done once per pixel, since the MCS
> value is shared between all samples belonging to a pixel.
>
> - When reading color values from the surface, we need to use the
> ld2dms sampler message instead of the ld2dss message, and we need to
> provide the value read from the MCS buffer as an argument.
> ---
> src/mesa/drivers/dri/i965/brw_blorp_blit.cpp | 45 ++++++++++++++++++++++++-
> 1 files changed, 43 insertions(+), 2 deletions(-)
I see an easy optimization that's suitable for a small follow-up patch. But this
code works and passes tests, so let's commit it as-is first.
This patch is
Reviewed-by: Chad Versace <chad.vers...@linux.intel.com>
> @@ -1126,8 +1148,13 @@ brw_blorp_blit_program::texel_fetch(struct brw_reg dst)
> break;
> case 7:
> if (key->tex_samples > 0) {
> - texture_lookup(dst, GEN7_SAMPLER_MESSAGE_SAMPLE_LD2DSS,
> - gen7_ld2dss_args, ARRAY_SIZE(gen7_ld2dss_args));
> + if (key->tex_layout == INTEL_MSAA_LAYOUT_CMS) {
> + texture_lookup(dst, GEN7_SAMPLER_MESSAGE_SAMPLE_LD2DMS,
> + gen7_ld2dms_args, ARRAY_SIZE(gen7_ld2dms_args));
> + } else {
> + texture_lookup(dst, GEN7_SAMPLER_MESSAGE_SAMPLE_LD2DSS,
> + gen7_ld2dss_args, ARRAY_SIZE(gen7_ld2dss_args));
> + }
The hw docs suggest here "a simple optimization with probable large return in
performance". If mcs_data == 0, which should be the common case for most
fragments, then only sample array slice 0 needs to be accessed. That is, when
tex_layout is CMS then we should emit code like this here:
if (mcs_data == 0) {
ld2dss(S, X, Y);
} else {
ld2dms(S, mcs_data, X, Y);
}
----
Chad Versace
chad.vers...@linux.intel.com
_______________________________________________
mesa-dev mailing list
mesa-dev@lists.freedesktop.org
http://lists.freedesktop.org/mailman/listinfo/mesa-dev
