https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109011
--- Comment #22 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:87c9bae4e32b54829dce0a93ff735412d5f684f8 commit r14-121-g87c9bae4e32b54829dce0a93ff735412d5f684f8 Author: Jakub Jelinek <ja...@redhat.com> Date: Thu Apr 20 19:44:27 2023 +0200 tree-vect-patterns: One small vect_recog_ctz_ffs_pattern tweak [PR109011] I've noticed I've made a typo, ifn in this function this late is always only IFN_CTZ or IFN_FFS, never IFN_CLZ. Due to this typo, we weren't using the originally intended .CTZ (X) = .POPCOUNT ((X - 1) & ~X) but .CTZ (X) = PREC - .POPCOUNT (X | -X) instead when we want to emit __builtin_ctz*/.CTZ using .POPCOUNT. Both compute the same value, both are defined at 0 with the same value (PREC), both have same number of GIMPLE statements, but I think the former ought to be preferred, because lots of targets have andn as a single operation rather than two, and also putting a -1 constant into a vector register is often cheaper than vector with broadcast PREC power of two value. 2023-04-20 Jakub Jelinek <ja...@redhat.com> PR tree-optimization/109011 * tree-vect-patterns.cc (vect_recog_ctz_ffs_pattern): Use .CTZ (X) = .POPCOUNT ((X - 1) & ~X) in preference to .CTZ (X) = PREC - .POPCOUNT (X | -X).
