On July 21, 2015 11:38:31 AM GMT+02:00, Jakub Jelinek <ja...@redhat.com> wrote: >On Tue, Jul 21, 2015 at 09:15:31AM +0000, Hurugalawadi, Naveen wrote: >> Please find attached the patch which performs following patterns >folding >> in match.pd:- >> >> a ==/!= a p+ b to b ==/!= 0. >> a << N ==/!= 0 to a&(-1>>N) ==/!= 0. > >Not sure about this second one. Why do you think it is generally >beneficial? On many targets, shifts are as fast as bitwise and, and >-1>>N could be e.g. significantly more expensive constant (say require >3 instructions to construct).
And may set flags while shift not? Of course we do a very poor job of representing this kind of stuff on gimple. Richard. > Jakub
