The SIMD splitting pass does not handle wide force_writemask_all
instructions correctly at the moment. For example, a SIMD32 TXF
on pre-Xe2 would get split to a pair of SIMD16. But it will set
the groups to operate on channels 15:0 and 31:16. That's not what
we want for a NoMask instruction - both should be 15:0, i.e.
bld.group(inst->exec_size, 0).
We could (and perhaps should) fix the SIMD splitting pass to handle
this, but the pass already has subtle complexity in which builders
are used. Or we could alter fs_builder::group(), but that has broader
implications. As a stop-gap, just make opt_combine_covergent_txfs stop
relying on SIMD splitting. It's trivial to do and fixes the issue
without risking other breakage.
Fixes: 6341b3cd87 ("brw: Combine convergent texture buffer fetches into fewer loads")
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/32714>
cb756ae8a2