https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107195
--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Aldy Hernandez <al...@gcc.gnu.org>: https://gcc.gnu.org/g:c4d15dddf6b9eacb36f535807ad2ee364af46e04 commit r13-3217-gc4d15dddf6b9eacb36f535807ad2ee364af46e04 Author: Aldy Hernandez <al...@redhat.com> Date: Mon Oct 10 20:42:10 2022 +0200 [PR107195] Set range to zero when nonzero mask is 0. When solving 0 = _15 & 1, we calculate _15 as: [irange] int [-INF, -2][0, +INF] NONZERO 0xfffffffe The known value of _15 is [0, 1] NONZERO 0x1 which is intersected with the above, yielding: [0, 1] NONZERO 0x0 This eventually gets copied to a _Bool [0, 1] NONZERO 0x0. This is problematic because here we have a bool which is zero, but returns false for irange::zero_p, since the latter does not look at nonzero bits. This causes logical_combine to assume the range is not-zero, and all hell breaks loose. I think we should just normalize a nonzero mask of 0 to [0, 0] at creation, thus avoiding all this. PR tree-optimization/107195 gcc/ChangeLog: * value-range.cc (irange::set_range_from_nonzero_bits): Set range to [0,0] when nonzero mask is 0. gcc/testsuite/ChangeLog: * gcc.dg/tree-ssa/pr107195-1.c: New test. * gcc.dg/tree-ssa/pr107195-2.c: New test.
