https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64946
--- Comment #17 from Shiva Chen <shiva0217 at gmail dot com> --- Hi, Richard Thanks for the explanation :) So the transformation (short)abs((int)short_var) -> abs (short_var) should guard by TYPE_OVERFLOW_WRAPS because when TYPE_OVERFLOW_WRAPS is true, signed operation could wrap around.(ABS_EXPR in gimple could wrap around and rtl abs already modulo) Therefore, the transformation is valid when TYPE_OVERFLOW_WRAPS is true. It seems the last update of Matthew's patch in https://gcc.gnu.org/ml/gcc-patches/2016-01/msg00433.html still make sense. Why would it be dropped, or there're still something we should consider ? If we implement ABSU_EXPR, when should transfer ABS_EXPR (x) -> (type of x) ABSU_EXPR (x) ? Could we define like if (!TYPE_OVERFLOW_WRAPS) then transfer ABS_EXPR (x) -> (type of x) ABSU_EXPR (x) in match.pd ? How to expand (type of x) ABSU_EXPR (x) to rtl ? Do we have to add a new naming pattern absu ?
