https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109964
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> --- So the bug in the vectorizer is that it does t.ii:14:5: note: can narrow to signed:16 without loss of precision: _31 = 1 >> _30; t.ii:14:5: note: only the low 16 bits of _30 are significant while that's correct that's not the proper constraint to check for in vect_recog_over_widening_pattern I think. That has code to deal with overflow for plus/minus/mult but no defense against shifts (that's also not a vect_truncatable_operation_p, so maybe it should simply check that)
