https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78726
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Most likely one of the endless reassoc bugs not properly updating or invalidating range information. Before reassoc1 we have: # RANGE [4294967040, 4294967295] a_11 = (unsigned int) _3; c.1_4 = c; # RANGE [0, 255] NONZERO 255 _5 = (unsigned int) c.1_4; # RANGE ~[1, 4294902015] _6 = _5 * a_11; # RANGE ~[1, 4278320895] _7 = _5 * _6; which looks correct, a_11 is int [-256, 1] converted to unsigned int, and c is unsigned char. But reassoc1 turns this into: # RANGE [4294967040, 4294967295] a_11 = (unsigned int) _3; c.1_4 = c; # RANGE [0, 255] NONZERO 255 _5 = (unsigned int) c.1_4; # RANGE ~[1, 4278320895] _7 = _5 * _5; _13 = _7 + 1023094746; _14 = _13 * a_11; It should have reused the SSA_NAME (_7) for something different, _5 * _5 has a range of [0, 65025] and could have been used in debug stmts later on.