[Mesa-dev] [PATCH 8/9] i965/vec4: Handle saturated constants in opt_vector_float

[Jason Ekstrand]

On Thu, Mar 17, 2016 at 11:18 AM, Matt Turner <mattst88 at gmail.com> wrote:

> On Thu, Mar 17, 2016 at 10:21 AM, Jason Ekstrand <jason at jlekstrand.net>
> wrote:
> > ---
> >  src/mesa/drivers/dri/i965/brw_vec4.cpp | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/src/mesa/drivers/dri/i965/brw_vec4.cpp
> b/src/mesa/drivers/dri/i965/brw_vec4.cpp
> > index 155a550..02a00b3 100644
> > --- a/src/mesa/drivers/dri/i965/brw_vec4.cpp
> > +++ b/src/mesa/drivers/dri/i965/brw_vec4.cpp
> > @@ -384,7 +384,13 @@ vec4_visitor::opt_vector_float()
> >           continue;
> >        }
> >
> > -      int vf = brw_float_to_vf(inst->src[0].f);
> > +      float f = inst->src[0].f;
> > +      if (inst->saturate) {
> > +         assert(inst->dst.type == BRW_REGISTER_TYPE_F);
> > +         f = CLAMP(f, 0.0f, 1.0f);
> > +      }
> > +
> > +      int vf = brw_float_to_vf(f);
> >        if (vf == -1)
> >           continue;
>
> Presumably the previous patch is to allow this to happen without
> thinking about types.
>
> This does look like a legitimate bug fix, but what does this fix or enable?
>

Patch 9 removes the mov.sat optimization from opt_algebraic which was
fixing up saturated constants before opt_vector_float ever saw them.  When
I removed it, I got a bunch of piglit fails from things that were writing
out-of-bounds constant values to auto-clampped outputs.  The problem was
that opt_vector_float was just throwing the .sat away.
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