[PATCH, rs6000] Fold vector absolutes in GIMPLE

[Richard Biener]

On May 29, 2017 12:24:44 PM GMT+02:00, Segher Boessenkool <segher@kernel.crashing.org> wrote:
>On Mon, May 29, 2017 at 10:32:18AM +0200, Richard Biener wrote:
>> On Fri, May 26, 2017 at 7:19 PM, Will Schmidt
><will_schmidt@vnet.ibm.com> wrote:
>> > Add support for early expansion of vector absolute built-ins.
>> >
>> > Bootstraps currently running (p7,p8le,p8be).
>> >
>> > OK for trunk?
>> 
>> What's the documented behavior for vec_abs with respect to an
>argument
>> of value INT_MIN?
>
>The documentation says:
>
>	"For integer vectors, the arithmetic is modular."

This means that folding as ABS_EXPR is not safe for !TYPE_OVERFLOW_WRAPS
Integral vector types.

Richard.

>http://openpowerfoundation.org/wp-content/uploads/resources/leabi-prd/
>(appendix A; the PDF is easier to read).
>
>
>Segher