https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102622
--- Comment #20 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The trunk branch has been updated by Andrew Pinski <pins...@gcc.gnu.org>: https://gcc.gnu.org/g:882d806c1a8f9d2d2ade1133de88d63e5d4fe40c commit r12-4276-g882d806c1a8f9d2d2ade1133de88d63e5d4fe40c Author: Andrew Pinski <apin...@marvell.com> Date: Sun Oct 10 01:28:59 2021 +0000 tree-optimization: [PR102622]: wrong code due to signed one bit integer and "a?-1:0" So it turns out this is kinda of a latent bug but not really latent. In GCC 9 and 10, phi-opt would transform a?-1:0 (even for signed 1-bit integer) to -(type)a but the type is an one bit integer which means the negation is undefined. GCC 11 fixed the problem by checking for a?pow2cst:0 transformation before a?-1:0 transformation. When I added the transformations to match.pd, I had swapped the order not paying attention and I didn't expect anything of it. Because there was no testcase failing due to this. Anyways this fixes the problem on the trunk by swapping the order in match.pd and adding a comment of why the order is this way. I will try to come up with a patch for GCC 9 and 10 series later on which fixes the problem there too. Note I didn't include the original testcase which requires the vectorizer and AVX-512f as I can't figure out the right dg options to restrict it to avx-512f but I did come up with a testcase which shows the problem and even more shows the problem with the 9/10 series as mentioned. OK? Bootstrapped and tested on x86_64-linux-gnu. PR tree-optimization/102622 gcc/ChangeLog: * match.pd: Swap the order of a?pow2cst:0 and a?-1:0 transformations. Swap the order of a?0:pow2cst and a?0:-1 transformations. gcc/testsuite/ChangeLog: * gcc.c-torture/execute/bitfld-10.c: New test.