https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94783
--- Comment #4 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:a0d732eea2e152fc51f7c5249abaa9ef56fc5121 commit r11-195-ga0d732eea2e152fc51f7c5249abaa9ef56fc5121 Author: Jakub Jelinek <ja...@redhat.com> Date: Fri May 8 09:35:41 2020 +0200 match.pd: Canonicalize (X + (X >> (prec - 1))) ^ (X >> (prec - 1)) to abs (X) [PR94783] The following patch canonicalizes M = X >> (prec - 1); (X + M) ^ M for signed integral types into ABS_EXPR (X). For X == min it is already UB because M is -1 and min + -1 is UB, so we can use ABS_EXPR rather than say ABSU_EXPR + cast. The backend might then emit the abs code back using the shift and addition and xor if it is the best sequence for the target, but could do something different that is better. 2020-05-08 Jakub Jelinek <ja...@redhat.com> PR tree-optimization/94783 * match.pd ((X + (X >> (prec - 1))) ^ (X >> (prec - 1)) to abs (X)): New simplification. * gcc.dg/tree-ssa/pr94783.c: New test.
