On Mon, May 23, 2022 at 10:59 AM Roger Sayle <ro...@nextmovesoftware.com> wrote: > > > Hi Uros, > > Thanks for the speedy review. The point of this patch is that (with > pending changes to STV) the pand;pxor sequence isn't created until > after combine, and hence doesn't/won't get caught by any of the > current pre-reload/combine splitters.
IMO this happens due to inconsistencies between integer and vector set, where integer andn is absent without BMI. However, we don't re-run the combine after reload, and I don't think it is worth to reimplement it via peephole2 patterns. Please note that AVX allows much more combinations that are not catched by your patch, and considering that combine already does the transformation, I don't see a compelling reason for this very specialized peephole2. Let's keep the patch shelved until a testcase shows the benefits of the patch. Uros. > > > > -----Original Message----- > > From: Uros Bizjak <ubiz...@gmail.com> > > Sent: 23 May 2022 09:51 > > To: Roger Sayle <ro...@nextmovesoftware.com> > > Cc: gcc-patches@gcc.gnu.org > > Subject: Re: [x86 PING] Peephole pand;pxor into pandn > > > > On Mon, May 23, 2022 at 10:44 AM Roger Sayle > > <ro...@nextmovesoftware.com> wrote: > > > > > > > > > This is a ping of a patch from April (a dependency of another stage1 > > > patch): > > > https://gcc.gnu.org/pipermail/gcc-patches/2022-April/593123.html > > > > > > This patch has been refreshed/retested against gcc 13 trunk on > > > x86_64-pc-linux-gnu with make bootstrap and make -k check, both with > > > and without --target_board=unix{-m32}, with no new failures. > > > Ok for mainline? > > > > I think this should be handled in a pre-reload splitter (or perhaps combine > > splitter). We have so many variants of SSE/AVX logic instructions that the > > transform after reload barely makes sense (please see the number of regno > > checks in the proposed patch). > > > > Uros. > > > > > 2022-05-23 Roger Sayle <ro...@nextmovesoftware.com> > > > > > > gcc/ChangeLog > > > * config/i386/sse.md (peephole2): Convert suitable pand followed > > > by pxor into pandn, i.e. (X&Y)^X into X & ~Y. > > > > > > Many thanks in advance, > > > Roger > > > -- > > > >
