From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) by sourceware.org (Postfix) with ESMTP id 126A038532F7; Fri, 25 Nov 2022 14:44:11 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 126A038532F7 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=kernel.crashing.org Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 2APEhAof025086; Fri, 25 Nov 2022 08:43:10 -0600 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 2APEh9Nn025079; Fri, 25 Nov 2022 08:43:09 -0600 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Fri, 25 Nov 2022 08:43:09 -0600 From: Segher Boessenkool To: "Kewen.Lin" Cc: Jiufu Guo , dje.gcc@gmail.com, linkw@gcc.gnu.org, gcc-patches@gcc.gnu.org Subject: Re: [PATCH V2] rs6000: Support to build constants by li/lis+oris/xoris Message-ID: <20221125144309.GG25951@gate.crashing.org> References: <20221026114052.17713-1-guojiufu@linux.ibm.com> <9331dba8-f346-37e5-3340-055f2c4d9245@linux.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9331dba8-f346-37e5-3340-055f2c4d9245@linux.ibm.com> User-Agent: Mutt/1.4.2.3i X-Spam-Status: No, score=-3.0 required=5.0 tests=BAYES_00,JMQ_SPF_NEUTRAL,KAM_DMARC_STATUS,KAM_SHORT,SPF_HELO_PASS,SPF_PASS,TXREP autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: Hi guys, On Fri, Nov 25, 2022 at 04:11:49PM +0800, Kewen.Lin wrote: > on 2022/10/26 19:40, Jiufu Guo wrote: > for "li/lis + oris/xoris", I interpreted it into four combinations: > > li + oris, lis + oris, li + xoris, lis + xoris. > > not sure just me interpreting like that, but the actual combinations > which this patch adopts are: > > li + oris, li + xoris, lis + xoris. > > It's a bit off, but not a big deal, up to you to reword it or not. :) The first two are obvious, but the last one is almost never a good idea, there usually are better ways to do the same. I cannot even think of any case where this is best? A lis;rl* is always prefered (it can optimise better, be combined with other insns). > > + HOST_WIDE_INT orig_c = c; If you ever feel you need a variable to hold an "orig" value, that is a good hint that you should restructure the code a bit, perhaps even factor it. That often is overdue (like here), not caused by you, but you could help solve it ;-) (This is what made this patch hard to review, btw). > > gen_rtx_IOR (DImode, copy_rtx (temp), > > GEN_INT (ud1))); > > } > > + else if ((ud4 == 0xffff && ud3 == 0xffff) > > + && ((ud1 & 0x8000) || (ud1 == 0 && !(ud2 & 0x8000)))) > > + { > > + temp = !can_create_pseudo_p () ? dest : gen_reg_rtx (DImode); > > + > > + HOST_WIDE_INT imm = (ud1 & 0x8000) ? ((ud1 ^ 0x8000) - 0x8000) > > + : ((ud2 << 16) - 0x80000000); We really should have some "hwi::sign_extend (ud1, 16)" helper function, heh. Maybe there already is? Ah, "sext_hwi". Fixing that up everywhere in this function is preapproved. > > + else > > + { > > + emit_move_insn (temp, > > + GEN_INT (((ud2 << 16) ^ 0x80000000) - 0x80000000)); > > + if (ud1 != 0) > > + emit_move_insn (temp, gen_rtx_IOR (DImode, temp, GEN_INT (ud1))); > > + emit_move_insn (dest, > > + gen_rtx_ZERO_EXTEND (DImode, > > + gen_lowpart (SImode, temp))); > > + } Why this? Please just write it in DImode, do not go via SImode? > > --- /dev/null > > +++ b/gcc/testsuite/gcc.target/powerpc/pr106708.h > > @@ -0,0 +1,9 @@ > > +/* Test constants which can be built by li/lis + oris/xoris */ > > +void __attribute__ ((__noinline__, __noclone__)) foo (long long *arg) > > +{ > > + *arg++ = 0x98765432ULL; > > + *arg++ = 0xffffffff7cdeab55ULL; > > + *arg++ = 0xffffffff65430000ULL; > > +} Use noipa please (it is shorter, simpler, and covers more :-) ) Could you comment what exact instructions are expected? li;xoris and li;xoris and lis;xoris I guess? It helps if you just tell the reader here. The li;oris and li;xoris parts look good. Segher