https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103037
--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> --- We have: var_3.2_4 = var_3; iftmp.1_14 = (int) var_3.2_4; var_11_lsm.14_8 = _7(D); <bb 3> [local count: 955630225]: # RANGE [0, 24] NONZERO 31 # a_20 = PHI <a_18(10), 0(9)> _19 = MEM <short unsigned int[23]> [(short unsigned int &)&arr_4][a_20]; if (_19 > 1) goto <bb 5>; [50.00%] else goto <bb 4>; [50.00%] <bb 4> [local count: 477815112]: # RANGE [0, 1] NONZERO 1 _3 = (int) _19; if (_19 != 0) goto <bb 5>; [20.00%] else goto <bb 6>; [80.00%] <bb 5> [local count: 477815112]: # RANGE [0, 1] NONZERO 1 # _24 = PHI <_3(4), 1(3)> # RANGE [1, 65535] NONZERO 65535 iftmp.1_15 = (int) _19; goto <bb 7>; [100.00%] <bb 6> [local count: 477815112]: <bb 7> [local count: 955630225]: # RANGE [-32768, 65535] # iftmp.1_10 = PHI <iftmp.1_15(5), iftmp.1_14(6)> # RANGE [0, 1] NONZERO 1 # _25 = PHI <_24(5), 0(6)> # RANGE [-1, 1] _5 = _25 / iftmp.1_10; and seems PRE is trying top simplify 1 / _3 and _3 / _3. _3 has correctly range of [0, 1] - in that bb _19 can't be anything but 0 or 1 given the condition, but iftmp.1_15 = (int) _19; isn't equivalent to that, because it is reachable from other bbs, even when it is also (int) _19. So, does PRE need to temporarily reset_flow_sensitive_info in such cases and restore if it didn't succeed?