[Mesa-dev] [PATCH] i965: fix the constant interp bitmask for flat mode

[Eric Anholt]

On Mon,  5 Sep 2011 15:59:32 +0800, Yuanhan Liu <yuanhan.liu at linux.intel.com> wrote:
> Fix the constant interpolation enable bit mask for flat light mode.
> FRAG_BIT_COL0 attribute bit might be 0, in which case we need to
> shift one more bit right.
> 
> This would fix the oglc specularColor test fail on both Sandybridge and
> Ivybridge.
> 
> Signed-off-by: Yuanhan Liu <yuanhan.liu at linux.intel.com>
> Signed-off-by: Xiang, Haihao <haihao.xiang at intel.com>
> ---
>  src/mesa/drivers/dri/i965/gen6_sf_state.c |   14 ++++++++++++--
>  src/mesa/drivers/dri/i965/gen7_sf_state.c |   14 ++++++++++++--
>  2 files changed, 24 insertions(+), 4 deletions(-)
> 
> diff --git a/src/mesa/drivers/dri/i965/gen6_sf_state.c b/src/mesa/drivers/dri/i965/gen6_sf_state.c
> index 5bb731d..2c954d8 100644
> --- a/src/mesa/drivers/dri/i965/gen6_sf_state.c
> +++ b/src/mesa/drivers/dri/i965/gen6_sf_state.c
> @@ -233,8 +233,18 @@ upload_sf_state(struct brw_context *brw)
>  
>     /* flat shading */
>     if (ctx->Light.ShadeModel == GL_FLAT) {
> -       dw17 |= ((brw->fragment_program->Base.InputsRead & (FRAG_BIT_COL0 | FRAG_BIT_COL1)) >>
> -                ((brw->fragment_program->Base.InputsRead & FRAG_BIT_WPOS) ? 0 : 1));
> +      /*
> +       * Setup the Constant Interpolation Enable bit mask for each
> +       * corresponding attribute(currently, we only care two attrs:
> +       * FRAG_BIT_COL0 and FRAG_BIT_COL1).
> +       *
> +       * FIXME: should we care other attributes?
> +       */
> +      dw17 = brw->fragment_program->Base.InputsRead & (FRAG_BIT_COL0 | FRAG_BIT_COL1);
> +      if ((brw->fragment_program->Base.InputsRead & FRAG_BIT_WPOS) == 0)
> +         dw17 >>= 1;
> +      if ((brw->fragment_program->Base.InputsRead & FRAG_BIT_COL0) == 0)
> +         dw17 >>= 1;
>     }

Seems like the code would be a lot more understandable if constant
interpolation was set up in the "for (attr = 0; attr < FRAG_ATTRIB_MAX;
attr++)" loop.  Plus then it would be obviously extendable when we do
the flat keyword support.
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