https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96928
--- Comment #2 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:576714b309b330df0e80e34114bcdf0bba35e146 commit r11-6472-g576714b309b330df0e80e34114bcdf0bba35e146 Author: Jakub Jelinek <ja...@redhat.com> Date: Tue Jan 5 16:35:22 2021 +0100 phiopt: Optimize x < 0 ? ~y : y to (x >> 31) ^ y [PR96928] As requested in the PR, the one's complement abs can be done more efficiently without cmov or branching. Had to change the ifcvt-onecmpl-abs-1.c testcase, we no longer optimize it in ifcvt, on x86_64 with -m32 we generate in the end the exact same code, but with -m64: movl %edi, %eax - notl %eax - cmpl %edi, %eax - cmovl %edi, %eax + sarl $31, %eax + xorl %edi, %eax ret 2021-01-05 Jakub Jelinek <ja...@redhat.com> PR tree-optimization/96928 * tree-ssa-phiopt.c (xor_replacement): New function. (tree_ssa_phiopt_worker): Call it. * gcc.dg/tree-ssa/pr96928.c: New test. * gcc.target/i386/ifcvt-onecmpl-abs-1.c: Remove -fdump-rtl-ce1, instead of scanning rtl dump for ifcvt message check assembly for xor instruction.
