[Bug tree-optimization/91198] GCC not generating AVX-512 compress/expand instructions

[raghesh.aloor at amd dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91198

--- Comment #9 from Raghesh Aloor <raghesh.aloor at amd dot com> ---
Updated patch available at the patch series starting from:
https://gcc.gnu.org/pipermail/gcc-patches/2026-June/722142.html

Richard had the following suggestion to perform the recognition of
compress pattern:

"We already have code to recognize a scatter with special
offset as "strided store" (for RISC-V IIRC), so one option is
to go with that approach, keep the scatter but recognize
the special offset and use a "compress-scatter" case here?"

This is again a prototype patch series to perfrom the above
suggestion. Please have a look at it and let us know if we are
in the right direction.

Please note that we tried to do only the first two phases mentioned
in the RFC: https://gcc.gnu.org/pipermail/gcc/2026-May/248167.html

Please note that there may be formatting issues in the patch, which
will be addressed once the approach is finalized.