[Mesa-dev] [PATCH v4 19/28] i965/vec4: fix SIMD-width lowering for VEC4_OPCODE_FROM_DOUBLE

[Francisco Jerez]

Samuel Iglesias Gonsálvez <siglesias at igalia.com> writes:

> On Wed, 2017-03-22 at 15:55 -0700, Francisco Jerez wrote:
>> Samuel Iglesias Gonsálvez <siglesias at igalia.com> writes:
>> 
>> > Now the VEC4_OPCODE_FROM_DOUBLE's destination data is written with
>> > stride 2. We need to take into account this when doing the split
>> > so we don't overwrite data.
>> > 
>> 
>> You should probably fix the destination type of your
>> VEC4_OPCODE_FROM_DOUBLE instructions in PATCH 17 instead so you don't
>> need to special-case VEC4_OPCODE_FROM_DOUBLE in this lowering pass.
>> 
>
> I don't think this would work. Do you mean to set the destination type
> to double, so horiz_offset() works fine here without any change?
>

Yes, double (or 64-bit integer) would be more appropriate than float,
because the opcode writes 64 bit-wide components, so using F as
destination type will inevitably confuse the optimizer.

> Then in the generator's code for VEC4_OPCODE_FROM_DOUBLE, I would need
> to retype the destination to... I don't know to which type because it
> was lost.
>
It would make a lot more sense to rename these after the destination
type (e.g. VEC4_OPCODE_TO_F32), since the conversion origin type is
fully determined by the source type encoded in the IR instruction, but
the destination type is not.

> Sam
>
>> > Signed-off-by: Samuel Iglesias Gonsálvez <siglesias at igalia.com>
>> > ---
>> >  src/intel/compiler/brw_vec4.cpp | 7 ++++++-
>> >  1 file changed, 6 insertions(+), 1 deletion(-)
>> > 
>> > diff --git a/src/intel/compiler/brw_vec4.cpp
>> > b/src/intel/compiler/brw_vec4.cpp
>> > index b26f8035811..f4eea954404 100644
>> > --- a/src/intel/compiler/brw_vec4.cpp
>> > +++ b/src/intel/compiler/brw_vec4.cpp
>> > @@ -2198,6 +2198,7 @@ vec4_visitor::lower_simd_width()
>> >           linst->group = channel_offset;
>> >           linst->size_written = size_written;
>> >  
>> > +         bool d2f_pass = (inst->opcode == VEC4_OPCODE_FROM_DOUBLE
>> > && n > 0);
>> >           /* Compute split dst region */
>> >           dst_reg dst;
>> >           if (needs_temp) {
>> > @@ -2212,7 +2213,11 @@ vec4_visitor::lower_simd_width()
>> >                 inst->insert_before(block, copy);
>> >              }
>> >           } else {
>> > -            dst = horiz_offset(inst->dst, channel_offset);
>> > +            /* d2x conversion is done with a destination's stride
>> > of 2. We need
>> > +             * to take into account when splitting it.
>> > +             */
>> > +            unsigned stride = d2f_pass ? 2 : 1;
>> > +            dst = horiz_offset(inst->dst, stride *
>> > channel_offset);
>> >           }
>> >           linst->dst = dst;
>> >  
>> > -- 
>> > 2.11.0
>> > 
>> > _______________________________________________
>> > mesa-dev mailing list
>> > mesa-dev at lists.freedesktop.org
>> > https://lists.freedesktop.org/mailman/listinfo/mesa-dev
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