on 2021/1/15 下午2:40, Kewen.Lin via Gcc-patches wrote: > Hi Segher, > > on 2021/1/15 上午8:50, Segher Boessenkool wrote: >> Hi! >> >> On Tue, Dec 22, 2020 at 04:08:26PM +0800, Kewen.Lin wrote: >>> This patch is to make unsigned int vector init go with >>> rldimi to merge two integers instead of shift and ior. >>> >>> I tried to use nonzero_bits in md file to make it more >>> general, but the testing shows it isn't doable. The >>> reason is that some passes would replace some pseudos >>> with other pseudos and do the recog again, but at that >>> time the nonzero_bits could get rough information and >>> lead the recog fails unexpectedly. >> >> Aha. So nonzero_bits is unusable for most purposes as well. Great :-/ >> >>> btw, the test case would reply on the combine patch[1]. >> >> Can you make a different testcase perhaps? This patch looks fine >> otherwise. >> > > Thanks! But I'm sorry that there is a typo, it should be "rely on" > rather than "reply on", without the patch[1] "combine: zeroing cost > for new copies", this test case doesn't get the desirable result. > I'll explain it more in that patch's thread. If your uncommitted > patch there with define_split and nonzero_bits works, this patch > can be discarded totally.
After the testing and the commit log shows, I realized that that patch can only work for three instruction combination, so this patch is still needed. BR, Kewen
