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

[Jason Ekstrand]

On Wed, Jul 1, 2015 at 11:44 PM, Iago Toral <itoral at igalia.com> wrote:
> 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?

Just pass the number of components into get_nir_src()?  That sounds fine to me.
--Jason

> 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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>