https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125357
--- Comment #5 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <[email protected]>: https://gcc.gnu.org/g:daf225605e85d17f5c6c1a205918e44b3b1eccba commit r17-593-gdaf225605e85d17f5c6c1a205918e44b3b1eccba Author: Jakub Jelinek <[email protected]> Date: Tue May 19 10:11:08 2026 +0200 i386: Use vpermilps for some non-const permutations [PR125357] We don't use vpermilps insn for V4S[IF]mode variable permutations on TARGET_AVX without TARGET_AVX512*. For TARGET_AVX512* there are plenty of permutation instructions already. For TARGET_AVX2, the function has special cases for one_operand_shuffle for V8SImode/V8SFmode and emits reasonable code, but for V4SImode/V4SFmode with TARGET_AVX2 it handles those using V8SImode/V8SFmode as two operand shuffle, which requires 2 preparation instructions, vpermd and one finalization instruction. And for !TARGET_AVX2 && TARGET_AVX we just emit terrible code for these. So, the following patch uses vpermilps for V4S[IF]mode one_operand_shuffle. Trying to handle V8S[IF]mode is not worth it, for TARGET_AVX2 we already emit good code (see above) and for !TARGET_AVX2 && TARGET_AVX V8SImode mask is not valid vector mode, so we emit terrible code no matter what. 2026-05-19 Jakub Jelinek <[email protected]> PR target/125357 * config/i386/i386-expand.cc (ix86_expand_vec_perm): For one_operand_shuffle if TARGET_AVX and not TARGET_AVX512F use vpermilps for V4SImode/V4SFmode. Formatting fix. * gcc.target/i386/avx-pr125357.c: New test. * gcc.target/i386/avx2-pr125357.c: New test. Reviewed-by: Hongtao Liu <[email protected]>
