[Mesa-dev] [PATCH v2 4/5] i965/clear: Simplify updating the indirect depth value

[Nanley Chery]

On Wed, Apr 25, 2018 at 04:50:11PM -0700, Jason Ekstrand wrote:
> On Tue, Apr 24, 2018 at 5:48 PM, Nanley Chery <nanleychery at gmail.com> wrote:
> 
> > Determine the predicate for updating the indirect depth value in the
> > loop which inspects whether or not we need to resolve any slices.
> > ---
> >  src/mesa/drivers/dri/i965/brw_clear.c | 43 +++++++++++++-----------------
> > -----
> >  1 file changed, 16 insertions(+), 27 deletions(-)
> >
> > diff --git a/src/mesa/drivers/dri/i965/brw_clear.c
> > b/src/mesa/drivers/dri/i965/brw_clear.c
> > index 6521141d7f6..e372d28926e 100644
> > --- a/src/mesa/drivers/dri/i965/brw_clear.c
> > +++ b/src/mesa/drivers/dri/i965/brw_clear.c
> > @@ -108,7 +108,6 @@ brw_fast_clear_depth(struct gl_context *ctx)
> >     struct intel_mipmap_tree *mt = depth_irb->mt;
> >     struct gl_renderbuffer_attachment *depth_att =
> > &fb->Attachment[BUFFER_DEPTH];
> >     const struct gen_device_info *devinfo = &brw->screen->devinfo;
> > -   bool same_clear_value = true;
> >
> >     if (devinfo->gen < 6)
> >        return false;
> > @@ -174,9 +173,16 @@ brw_fast_clear_depth(struct gl_context *ctx)
> >     const uint32_t num_layers = depth_att->Layered ?
> > depth_irb->layer_count : 1;
> >
> >     /* If we're clearing to a new clear value, then we need to resolve any
> > clear
> > -    * flags out of the HiZ buffer into the real depth buffer.
> > +    * flags out of the HiZ buffer into the real depth buffer and update
> > the
> > +    * miptree's clear value.
> >      */
> >     if (mt->fast_clear_color.f32[0] != clear_value) {
> > +      /* BLORP updates the indirect clear color buffer when we do fast
> > clears.
> > +       * If we won't do a fast clear, we'll have to update it ourselves.
> > Start
> > +       * off assuming we won't perform a fast clear.
> > +       */
> > +      bool blorp_will_update_indirect_color = false;
> >
> 
> This boolean is rather awkward.
> 
> 

Why's that?

> > +
> >        for (uint32_t level = mt->first_level; level <= mt->last_level;
> > level++) {
> >           if (!intel_miptree_level_has_hiz(mt, level))
> >              continue;
> > @@ -184,16 +190,20 @@ brw_fast_clear_depth(struct gl_context *ctx)
> >           const unsigned level_layers = brw_get_num_logical_layers(mt,
> > level);
> >
> >           for (uint32_t layer = 0; layer < level_layers; layer++) {
> > +            const enum isl_aux_state aux_state =
> > +               intel_miptree_get_aux_state(mt, level, layer);
> > +
> >              if (level == depth_irb->mt_level &&
> >                  layer >= depth_irb->mt_layer &&
> >                  layer < depth_irb->mt_layer + num_layers) {
> > +
> > +               if (aux_state != ISL_AUX_STATE_CLEAR)
> > +                  blorp_will_update_indirect_color = true;
> > +
> >                 /* We're going to clear this layer anyway.  Leave it
> > alone. */
> >                 continue;
> >              }
> >
> > -            enum isl_aux_state aux_state =
> > -               intel_miptree_get_aux_state(mt, level, layer);
> > -
> >              if (aux_state != ISL_AUX_STATE_CLEAR &&
> >                  aux_state != ISL_AUX_STATE_COMPRESSED_CLEAR) {
> >                 /* This slice doesn't have any fast-cleared bits. */
> > @@ -214,29 +224,8 @@ brw_fast_clear_depth(struct gl_context *ctx)
> >        }
> >
> >        intel_miptree_set_depth_clear_value(brw, mt, clear_value);
> > -      same_clear_value = false;
> > -   }
> > -
> > -   bool need_clear = false;
> > -   for (unsigned a = 0; a < num_layers; a++) {
> > -      enum isl_aux_state aux_state =
> > -         intel_miptree_get_aux_state(mt, depth_irb->mt_level,
> > -                                     depth_irb->mt_layer + a);
> > -
> > -      if (aux_state != ISL_AUX_STATE_CLEAR) {
> > -         need_clear = true;
> > -         break;
> > -      }
> > -   }
> > -
> > -   if (!need_clear) {
> > -      if (!same_clear_value) {
> > -         /* BLORP updates the indirect clear color buffer when performing
> > a
> > -          * fast clear. Since we are skipping the fast clear here, we
> > need to
> > -          * do the update ourselves.
> > -          */
> > +      if (!blorp_will_update_indirect_color)
> >           intel_miptree_update_indirect_color(brw, mt);
> > -      }
> >
> 
> I think we can do this even better.  We could do
> 
> bool blorp_updated_indirect_clear_color = false;
> 
> and then set it to true if we call intel_hiz_exec below.  Then, after the
> loop below we would do
> 
> if (!blorp_updated_indirect_clear_color)
>    intel_miptree_update_indirect_color(brw, mt);
> 
> after we've done the clears.
> 
> 

I had something like that originally and I think that solution would
have marginally better performance. I went with doing it this way
because it allows us to:

* Do all the clear color updates in one place.
* Place blorp_will_update_indirect_color in a scope smaller
  than the function.
* Delete more code.

If we wait until the loop below to assign
blorp_updated_indirect_clear_color, we have to keep the same_clear_value
variable around and then do:

if (!blorp_updated_indirect_clear_color && !same_clear_value)
   intel_miptree_update_indirect_color(brw, mt);

-Nanley

> >     }
> >
> >     for (unsigned a = 0; a < num_layers; a++) {
> > --
> > 2.16.2
> >
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> >