[Mesa-dev] [PATCH 7/8] i965/gen7: Enable the features required for GL_ARB_sample_shading

[Paul Berry]

On 14 October 2013 10:12, Anuj Phogat <anuj.phogat at gmail.com> wrote:

> - Enable GEN7_WM_MSDISPMODE_PERSAMPLE, GEN7_WM_POSOFFSET_SAMPLE,
>   GEN7_WM_OMASK_TO_RENDER_TARGET as per extension's specification.
> - Don't enable GEN7_WM_16_DISPATCH_ENABLE when GEN7_WM_MSDISPMODE_PERSAMPLE
>   is enabled. Refer IVB PRM Vol. 2, Part 1, Page 288 for details.
>
> Signed-off-by: Anuj Phogat <anuj.phogat at gmail.com>
>

My comments on patch 6 apply here as well.


> ---
>  src/mesa/drivers/dri/i965/gen7_wm_state.c | 70
> +++++++++++++++++++++++++++++--
>  1 file changed, 67 insertions(+), 3 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/gen7_wm_state.c
> b/src/mesa/drivers/dri/i965/gen7_wm_state.c
> index a2046c3..0267e0e 100644
> --- a/src/mesa/drivers/dri/i965/gen7_wm_state.c
> +++ b/src/mesa/drivers/dri/i965/gen7_wm_state.c
> @@ -82,9 +82,15 @@ upload_wm_state(struct brw_context *brw)
>        GEN7_WM_BARYCENTRIC_INTERPOLATION_MODE_SHIFT;
>
>     /* _NEW_COLOR, _NEW_MULTISAMPLE */
> +   /* Enable if the pixel shader kernel generates and outputs oMask.
> +    */
>     if (fp->program.UsesKill || ctx->Color.AlphaEnabled ||
> -       ctx->Multisample.SampleAlphaToCoverage)
> +       ctx->Multisample.SampleAlphaToCoverage ||
> +       (ctx->Multisample.SampleShading &&
> +        (fp->program.Base.OutputsWritten &
> +         BITFIELD64_BIT(FRAG_RESULT_SAMPLE_MASK)))) {
>        dw1 |= GEN7_WM_KILL_ENABLE;
> +   }
>
>     /* _NEW_BUFFERS */
>     if (brw_color_buffer_write_enabled(brw) || writes_depth ||
> @@ -97,7 +103,25 @@ upload_wm_state(struct brw_context *brw)
>           dw1 |= GEN7_WM_MSRAST_ON_PATTERN;
>        else
>           dw1 |= GEN7_WM_MSRAST_OFF_PIXEL;
> -      dw2 |= GEN7_WM_MSDISPMODE_PERPIXEL;
> +      /* From arb_sample_shading specification:
> +       * "If MULTISAMPLE or SAMPLE_SHADING_ARB is disabled, sample shading
> +       *  has no effect."
> +       *
> +       * "Using gl_SampleID in a fragment shader causes the entire shader
> +       *  to be evaluated per-sample."
> +       * "Using gl_SamplePosition in a fragment shader causes the entire
> +       *  shader to be evaluated per-sample."
> +       *
> +       *  I interprate the above four lines as enable the sample shading
> +       *  if fragment shader uses gl_SampleID or gl_SamplePosition.
> +       */
> +      if (ctx->Multisample.Enabled &&
> +          (ctx->Multisample.SampleShading ||
> +           brw->fragment_program->Base.InputsRead & VARYING_BIT_SAMPLE_ID
> ||
> +           brw->fragment_program->Base.InputsRead &
> VARYING_BIT_SAMPLE_POS))
> +         dw2 |= GEN7_WM_MSDISPMODE_PERSAMPLE;
> +      else
> +         dw2 |= GEN7_WM_MSDISPMODE_PERPIXEL;
>     } else {
>        dw1 |= GEN7_WM_MSRAST_OFF_PIXEL;
>        dw2 |= GEN7_WM_MSDISPMODE_PERSAMPLE;
> @@ -129,6 +153,8 @@ upload_ps_state(struct brw_context *brw)
>     uint32_t dw2, dw4, dw5;
>     const int max_threads_shift = brw->is_haswell ?
>        HSW_PS_MAX_THREADS_SHIFT : IVB_PS_MAX_THREADS_SHIFT;
> +   bool msdispmode_persample = false;
> +   bool multisampled_fbo = ctx->DrawBuffer->Visual.samples > 1;
>
>     /* BRW_NEW_PS_BINDING_TABLE */
>     BEGIN_BATCH(2);
> @@ -169,6 +195,34 @@ upload_ps_state(struct brw_context *brw)
>     if (brw->wm.prog_data->nr_params > 0)
>        dw4 |= GEN7_PS_PUSH_CONSTANT_ENABLE;
>
> +   /* From the IVB PRM, volume 2 part 1, page 287:
> +    * "This bit is inserted in the PS payload header and made available to
> +    * the DataPort (either via the message header or via header bypass) to
> +    * indicate that oMask data (one or two phases) is included in Render
> +    * Target Write messages. If present, the oMask data is used to mask
> off
> +    * samples."
> +    */
> +   if (ctx->Extensions.ARB_sample_shading &&
> +       (brw->fragment_program->Base.OutputsWritten &
> +        BITFIELD64_BIT(FRAG_RESULT_SAMPLE_MASK)))
> +      dw4 |= GEN7_PS_OMASK_TO_RENDER_TARGET;
> +
> +   /* From the IVB PRM, volume 2 part 1, page 287:
> +    * "If the PS kernel does not need the Position XY Offsets to
> +    * compute a Position Value, then this field should be programmed
> +    * to POSOFFSET_NONE."
> +    * "SW Recommendation: If the PS kernel needs the Position Offsets
> +    * to compute a Position XY value, this field should match Position
> +    * ZW Interpolation Mode to ensure a consistent position.xyzw
> +    * computation."
> +    * We only require XY sample offsets. So, this recommendation doesn't
> +    * look useful at the moment. We might need this in future.
> +    */
> +   if (brw->fragment_program->Base.InputsRead & VARYING_BIT_SAMPLE_POS)
> +      dw4 |= GEN7_PS_POSOFFSET_SAMPLE;
> +   else
> +      dw4 |= GEN7_PS_POSOFFSET_NONE;
> +
>     /* CACHE_NEW_WM_PROG | _NEW_COLOR
>      *
>      * The hardware wedges if you have this bit set but don't turn on any
> dual
> @@ -185,7 +239,17 @@ upload_ps_state(struct brw_context *brw)
>        dw4 |= GEN7_PS_ATTRIBUTE_ENABLE;
>
>     dw4 |= GEN7_PS_8_DISPATCH_ENABLE;
> -   if (brw->wm.prog_data->prog_offset_16)
> +   msdispmode_persample =
> +      ctx->Multisample.Enabled &&
> +      (ctx->Multisample.SampleShading ||
> +       brw->fragment_program->Base.InputsRead & VARYING_BIT_SAMPLE_ID ||
> +       brw->fragment_program->Base.InputsRead & VARYING_BIT_SAMPLE_POS);
> +
> +   /* In case of non 1x (i.e 4x, 8x) multisampling with
> MDISPMODE_PERSAMPLE,
> +    * only one of SIMD8 and SIMD16 should be enabled.
> +    */
> +   if (brw->wm.prog_data->prog_offset_16 &&
> +       !(multisampled_fbo && msdispmode_persample))
>        dw4 |= GEN7_PS_16_DISPATCH_ENABLE;
>
>     dw5 |= (brw->wm.prog_data->first_curbe_grf <<
> --
> 1.8.1.4
>
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