[Mesa-dev] [PATCH 03/10] intel/fs: Fix bug in lower_simd_width while splitting an instruction which was already split.

[Iago Toral]

On Mon, 2019-01-07 at 11:58 -0800, Francisco Jerez wrote:
> Iago Toral <itoral at igalia.com> writes:
> 
> > On Sat, 2018-12-29 at 12:38 -0800, Francisco Jerez wrote:
> > > This seems to be a problem in combination with the
> > > lower_regioning
> > > pass introduced by a future commit, which can modify a SIMD-split
> > > instruction causing its execution size to become illegal
> > > again.  A
> > > subsequent call to lower_simd_width() would hit this bug on a
> > > future
> > > platform.
> > > 
> > > Cc: mesa-stable at lists.freedesktop.org
> > > ---
> > >  src/intel/compiler/brw_fs.cpp | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/src/intel/compiler/brw_fs.cpp
> > > b/src/intel/compiler/brw_fs.cpp
> > > index 97544fdf465..4aacc72a1b7 100644
> > > --- a/src/intel/compiler/brw_fs.cpp
> > > +++ b/src/intel/compiler/brw_fs.cpp
> > > @@ -5666,7 +5666,7 @@ static fs_reg
> > >  emit_unzip(const fs_builder &lbld, fs_inst *inst, unsigned i)
> > >  {
> > >     /* Specified channel group from the source region. */
> > > -   const fs_reg src = horiz_offset(inst->src[i], lbld.group());
> > > +   const fs_reg src = horiz_offset(inst->src[i], lbld.group() -
> > > inst->group);
> > 
> > Should we assert that lbld.group >= inst->group? Same below.
> > 
> 
> The IR will fail validation anytime that's not the case.  But I can
> add
> the assertions in both places if that makes you feel more
> comfortable.

I guess you are referring to this assert at codegen time:

assert(inst->force_writemask_all || inst->group % inst->exec_size ==
0);

I guess that is probably enough, but I would still prefer to add the
asserts here too if that's okay.

> > >     if (needs_src_copy(lbld, inst, i)) {
> > >        /* Builder of the right width to perform the copy avoiding
> > > uninitialized
> > > @@ -5757,7 +5757,7 @@ emit_zip(const fs_builder &lbld_before,
> > > const
> > > fs_builder &lbld_after,
> > >     assert(lbld_before.group() == lbld_after.group());
> > >  
> > >     /* Specified channel group from the destination region. */
> > > -   const fs_reg dst = horiz_offset(inst->dst,
> > > lbld_after.group());
> > > +   const fs_reg dst = horiz_offset(inst->dst, lbld_after.group()
> > > -
> > > inst->group);
> > >     const unsigned dst_size = inst->size_written /
> > >        inst->dst.component_size(inst->exec_size);
> > >