https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81601
--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> --- The -Warray-bounds warning has false positives, so you can run into them and in that case using -Werror isn't really a good idea. The problem is that the same bitfield, tp->chrono_start, is accessed 2 different ways in the IL before vrp1: _5 = tp_2(D)->chrono_type; if (_5 == 0) in one spot, and _12 = BIT_FIELD_REF <*tp_2(D), 8, 128>; _13 = _12 & 3; if (_13 != 0) in another. The optimizers don't treat those two as the same thing, and we have thus _5 used in the first condition, _13 in second one and then again _5. >From the first condition it determines that _5 must be zero in that branch (that is the if (type > tp->chrono_type) condition, where you do nothing if tp->chrono_type is not 0), it doesn't know that also implies that _13 is 0 to optimize that as dead code, and finally sees array index of [_5 - 1], and when _5 is known to be 0, that means [-1], which is invalid. It is invalid, but in dead code.
