At 2022-11-08 22:58:34, "Richard Biener" <richard.guent...@gmail.com> wrote:
>On Sat, Nov 5, 2022 at 10:03 AM Zhongyunde via Gcc-patches ><gcc-patches@gcc.gnu.org> wrote: >> >> >> > -----Original Message----- >> > From: Andrew Pinski [mailto:pins...@gcc.gnu.org] >> > Sent: Saturday, November 5, 2022 2:34 PM >> > To: Zhongyunde <zhongyu...@huawei.com> >> > Cc: hongtao....@intel.com; gcc-patches@gcc.gnu.org; Zhangwen(Esan) >> > <zwzhangwen.zh...@huawei.com>; Weiwei (weiwei, Compiler) >> > <weiwe...@huawei.com>; zhong_1985...@163.com >> > Subject: Re: [PATCH] [PHIOPT] Add A ? B + CST : B match and simplify >> > optimizations >> > >> > On Fri, Nov 4, 2022 at 11:17 PM Zhongyunde <zhongyu...@huawei.com> >> > wrote: >> > > >> > > hi, >> > > This patch is try to fix the issue >> > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107190, >> > > would you like to give me some suggestion, thanks. >> > >> > This seems like a "simplified" version of >> > https://gcc.gnu.org/pipermail/gcc-patches/2021-November/584411.html >> > which just handles power of 2 constants where we know the cond will be >> > removed. >> > We could do even more "simplified" of 1 if needed really. >> > What is the IR before PHI-OPT? Is it just + 1? >> >> Thanks for your attention. It is + 4294967296 before PHI-OPT (See detail >> https://gcc.godbolt.org/z/6zEc6ja1z) >> So we should keep matching the power of 2 constants ? >> >> > Also your pattern can be simplified to use integer_pow2p in the match part >> > instead of INTEGER_CST. >> > >> Apply your comment, thanks > >How does the patch fix the mentioned bug? match.pd patterns should make things >"simpler" but x + (a << C') isn't simpler than a ? x + C : x. It >looks you are targeting >PHI-OPT here, so maybe instead extend value_replacement to handle this case, >it does look similar to the case with neutral/absorbing element there? > >Richard. Thanks. This patch try to fix the 1st issued mentioned in107090 – [aarch64] sequence logic should be combined with mul and umulh (gnu.org) Sure, I'll take a look at the function value_replacement. I have also noticed that the function of two_value_replacement is very close to patch I want to achieve, and it may be easy to extend. It seems can be expressed equally in match.pd (called by match_simplify_replacement), so how do we choose where to implement may be better? ``` | /* Do the replacement of conditional if it can be done. */if (!early_p && !diamond_p && two_value_replacement (bb, bb1, e2, phi, arg0, arg1)) cfgchanged = true; elseif (!diamond_p && match_simplify_replacement (bb, bb1, e1, e2, phi, arg0, arg1, early_p)) cfgchanged = true; | ``` >> > Thanks, >> > Andrew >> >>
