https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64946
--- Comment #9 from vekumar at gcc dot gnu.org --- This match.pd pattern vectorizes the PR but works only with -fwrapv. (simplify ( convert (abs (convert@1 @0))) ( if (INTEGRAL_TYPE_P (type) /* We check for type compatibility between @0 and @1 below, so there's no need to check that @1/@3 are integral types. */ && INTEGRAL_TYPE_P (TREE_TYPE (@0)) && INTEGRAL_TYPE_P (TREE_TYPE (@1)) /* The precision of the type of each operand must match the precision of the mode of each operand, similarly for the result. */ && (TYPE_PRECISION (TREE_TYPE (@0)) == GET_MODE_PRECISION (TYPE_MODE (TREE_TYPE (@0)))) && (TYPE_PRECISION (TREE_TYPE (@1)) == GET_MODE_PRECISION (TYPE_MODE (TREE_TYPE (@1)))) && TYPE_PRECISION (type) == GET_MODE_PRECISION (TYPE_MODE (type)) /* The inner conversion must be a widening conversion. */ && TYPE_PRECISION (TREE_TYPE (@1)) > TYPE_PRECISION (TREE_TYPE (@0)) && ((GENERIC && (TYPE_MAIN_VARIANT (TREE_TYPE (@0)) == TYPE_MAIN_VARIANT (type))) || (GIMPLE && types_compatible_p (TREE_TYPE (@0), type)))) (if (TYPE_OVERFLOW_WRAPS (TREE_TYPE (@0))) (abs @0)))) For default cases (when no -fwrapv is given), doing ABSE_EXPR(shorttype) will invoke undefined behaviour when value is -32678. similarly for signed char min. As per Richard suggestion we need to move to a new tree code ABSU_EXPR to do this type of folding optimization.