Hi Jakub, on 2019/7/15 下午4:59, Jakub Jelinek wrote: > On Mon, Jul 15, 2019 at 04:50:13PM +0800, Kewen.Lin wrote: >> In match.pd and expmed.c, we have some codes to transform lrotate to >> rrotate if rotation count is const. But they don't consider the target >> whether supports the rrotate. It leads to some suboptimal generated >> code since some optimization can't get expected result by querying >> target optab. One typical case is that we miss some rotation >> vectorization opportunity on Power. > > This will not do the right thing if neither lrotate nor rrotate is > supported, you want to canonicalize in that case IMHO. > The code formatting is wrong (|| at the end of line, overly long lines). > > Finally, what is the reason why Power doesn't support one of the rotates? > Especially for rotates by constant, you can transform those in the > define_expand. > > Canonicalizing code is highly desirable during GIMPLE, it means if you have > say left rotate by 23 in one spot and right rotate by bitsize - 23 in > another spot, e.g. SCCVN can merge that code. > > So, IMNSHO, just improve the backend. >
OK, I see. Thanks for the explanation. I'll try to fix it in the backend. Thanks, Kewen
