[Mesa-dev] [PATCH V2] i965: fix alpha test for MRT

[Ian Romanick]

On 07/02/2013 01:42 AM, Chris Forbes wrote:
> Include src0 alpha in the RT write message when using MRT, so it is used
> for the alpha test instead of the normal per-RT alpha value.
>
> Fixes broken rendering in Dota2 under Wine [FDO #62647].

Could you use the normative bugzilla reference, and add a note for the 
stable branches. :)

> No Piglit regressions on Ivybridge.
>
> V2: reuse (and simplify) existing sample_alpha_to_coverage flag in
> the FS key, rather than adding another redundant one.
>
> Signed-off-by: Chris Forbes <chrisf at ijw.co.nz>
> ---
>   src/mesa/drivers/dri/i965/brw_fs_emit.cpp    |  4 +---
>   src/mesa/drivers/dri/i965/brw_fs_visitor.cpp |  3 +--
>   src/mesa/drivers/dri/i965/brw_wm.c           | 10 ++++++----
>   src/mesa/drivers/dri/i965/brw_wm.h           |  2 +-
>   4 files changed, 9 insertions(+), 10 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_fs_emit.cpp b/src/mesa/drivers/dri/i965/brw_fs_emit.cpp
> index f390989..c158016 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs_emit.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs_emit.cpp
> @@ -127,9 +127,7 @@ fs_generator::generate_fb_write(fs_inst *inst)
>   		 retype(brw_vec8_grf(0, 0), BRW_REGISTER_TYPE_UD));
>   	 brw_set_compression_control(p, BRW_COMPRESSION_NONE);
>
> -         if (inst->target > 0 &&
> -	     c->key.nr_color_regions > 1 &&
> -	     c->key.sample_alpha_to_coverage) {
> +         if (inst->target > 0 && c->key.replicate_alpha) {
>               /* Set "Source0 Alpha Present to RenderTarget" bit in message
>                * header.
>                */
> diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
> index a67b6ed..3353f55 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
> @@ -2254,8 +2254,7 @@ fs_visitor::emit_fb_writes()
>      if (header_present) {
>         src0_alpha_to_render_target = intel->gen >= 6 &&
>   				    !do_dual_src &&
> -				    c->key.nr_color_regions > 1 &&
> -				    c->key.sample_alpha_to_coverage;
> +                                    c->key.replicate_alpha;
>         /* m2, m3 header */
>         nr += 2;
>      }
> diff --git a/src/mesa/drivers/dri/i965/brw_wm.c b/src/mesa/drivers/dri/i965/brw_wm.c
> index 6eb4a1d..5f681f6 100644
> --- a/src/mesa/drivers/dri/i965/brw_wm.c
> +++ b/src/mesa/drivers/dri/i965/brw_wm.c
> @@ -277,8 +277,8 @@ brw_wm_debug_recompile(struct brw_context *brw,
>                         old_key->flat_shade, key->flat_shade);
>      found |= key_debug(intel, "number of color buffers",
>                         old_key->nr_color_regions, key->nr_color_regions);
> -   found |= key_debug(intel, "sample alpha to coverage",
> -                      old_key->sample_alpha_to_coverage, key->sample_alpha_to_coverage);
> +   found |= key_debug(intel, "MRT alpha test or alpha-to-coverage",
> +                      old_key->replicate_alpha, key->replicate_alpha);
>      found |= key_debug(intel, "rendering to FBO",
>                         old_key->render_to_fbo, key->render_to_fbo);
>      found |= key_debug(intel, "fragment color clamping",
> @@ -461,8 +461,10 @@ static void brw_wm_populate_key( struct brw_context *brw,
>
>      /* _NEW_BUFFERS */
>      key->nr_color_regions = ctx->DrawBuffer->_NumColorDrawBuffers;
> -  /* _NEW_MULTISAMPLE */
> -   key->sample_alpha_to_coverage = ctx->Multisample.SampleAlphaToCoverage;
> +
> +   /* _NEW_MULTISAMPLE, _NEW_COLOR, _NEW_BUFFERS */
> +   key->replicate_alpha = ctx->DrawBuffer->_NumColorDrawBuffers > 1 &&
> +      (ctx->Multisample.SampleAlphaToCoverage || ctx->Color.AlphaEnabled);
>
>      /* BRW_NEW_VUE_MAP_GEOM_OUT */
>      if (intel->gen < 6)
> diff --git a/src/mesa/drivers/dri/i965/brw_wm.h b/src/mesa/drivers/dri/i965/brw_wm.h
> index 28e8734..57db27f 100644
> --- a/src/mesa/drivers/dri/i965/brw_wm.h
> +++ b/src/mesa/drivers/dri/i965/brw_wm.h
> @@ -62,7 +62,7 @@ struct brw_wm_prog_key {
>      GLuint stats_wm:1;
>      GLuint flat_shade:1;
>      GLuint nr_color_regions:5;
> -   GLuint sample_alpha_to_coverage:1;
> +   GLuint replicate_alpha:1;
>      GLuint render_to_fbo:1;
>      GLuint clamp_fragment_color:1;
>      GLuint line_aa:2;
>