[Mesa-dev] [PATCH 13/78] i965/nir/vec4: Implement conditional statements (nir_cf_node_if)

[Iago Toral]

On Tue, 2015-06-30 at 09:30 -0700, Jason Ekstrand wrote:
> On Fri, Jun 26, 2015 at 1:06 AM, Eduardo Lima Mitev <elima at igalia.com> wrote:
> > From: Iago Toral Quiroga <itoral at igalia.com>
> >
> > The same we do in the FS NIR backend, only that here we need to consider
> > the number of components in the condition and adjust the swizzle
> > accordingly.
> >
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89580
> > ---
> >  src/mesa/drivers/dri/i965/brw_vec4_nir.cpp | 23 ++++++++++++++++++++++-
> >  1 file changed, 22 insertions(+), 1 deletion(-)
> >
> > diff --git a/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp b/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp
> > index 1ec75ee..d81b6a7 100644
> > --- a/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp
> > +++ b/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp
> > @@ -314,7 +314,28 @@ vec4_visitor::nir_emit_cf_list(exec_list *list)
> >  void
> >  vec4_visitor::nir_emit_if(nir_if *if_stmt)
> >  {
> > -   /* @TODO: Not yet implemented */
> > +   /* First, put the condition in f0 */
> > +   src_reg condition = get_nir_src(if_stmt->condition, BRW_REGISTER_TYPE_D);
> > +
> > +   int num_components = if_stmt->condition.is_ssa ?
> > +      if_stmt->condition.ssa->num_components :
> > +      if_stmt->condition.reg.reg->num_components;
> > +
> > +   condition.swizzle = brw_swizzle_for_size(num_components);
> > +
> > +   vec4_instruction *inst = emit(MOV(dst_null_d(), condition));
> > +   inst->conditional_mod = BRW_CONDITIONAL_NZ;
> 
> NIR if statements read only one component by definition.  There's no
> need to do this.

I see, we still need to do this explicitly though:

condition.swizzle = brw_swizzle_for_size(1);

Maybe we should just make get_nir_src() set the swizzle based on the
number of components instead so we don't have to do this kind of things
after calling that, does that sound better?

Iago

> 
> > +   emit(IF(BRW_PREDICATE_NORMAL));
> > +
> > +   nir_emit_cf_list(&if_stmt->then_list);
> > +
> > +   /* note: if the else is empty, dead CF elimination will remove it */
> > +   emit(BRW_OPCODE_ELSE);
> > +
> > +   nir_emit_cf_list(&if_stmt->else_list);
> > +
> > +   emit(BRW_OPCODE_ENDIF);
> >  }
> >
> >  void
> > --
> > 2.1.4
> >
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