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

[Iago Toral]

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.

>     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);
>