From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp-out2.suse.de (smtp-out2.suse.de [IPv6:2001:67c:2178:6::1d]) by sourceware.org (Postfix) with ESMTPS id ED4203858D35; Fri, 9 Jun 2023 12:53:00 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org ED4203858D35 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=suse.de Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=suse.de Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id 1D9771FDFA; Fri, 9 Jun 2023 12:53:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1686315180; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=QBpPKzBxGnsKcoLPHprb2OuYllxevYJ+vWm4Oi2B+Ok=; b=MXzTFtgTf55rpItYXgiMICClQum/f+lWOrpI9zVrUcRP+xAFECGmdtcoh8iikywN14BF3c AACc/IDdANi42EKiOM+61E48lhPDzIjRwitDQrwh/vDEIwP5pWgXAGBDFYHhRy4eGmlT/p svyY1PYMqVhCbT9n9Ailhpk/IiY3MPg= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1686315180; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=QBpPKzBxGnsKcoLPHprb2OuYllxevYJ+vWm4Oi2B+Ok=; b=+1T+LCL5mYhZnEvQFXw76LnpyUot0K7FqgE+T1gBgjrHrdgdOzWF7ySqh+i/Bfmplkmp4A 5IgSvzMrjbEZQDCw== Received: from wotan.suse.de (wotan.suse.de [10.160.0.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id F1B012C141; Fri, 9 Jun 2023 12:52:59 +0000 (UTC) Date: Fri, 9 Jun 2023 12:52:59 +0000 (UTC) From: Richard Biener To: Jiufu Guo cc: Richard Sandiford , gcc-patches@gcc.gnu.org, jeffreyalaw@gmail.com, segher@kernel.crashing.org, dje.gcc@gmail.com, linkw@gcc.gnu.org, bergner@linux.ibm.com Subject: Re: [PATCH] Make sure SCALAR_INT_MODE_P before invoke try_const_anchors In-Reply-To: <7no7lohklj.fsf@ltcden2-lp1.aus.stglabs.ibm.com> Message-ID: References: <20230609052847.2128612-1-guojiufu@linux.ibm.com> <56dbba43adda001d1668c29e8024c85d@linux.ibm.com> <7nwn0dgfvj.fsf@ltcden2-lp1.aus.stglabs.ibm.com> <7no7lohklj.fsf@ltcden2-lp1.aus.stglabs.ibm.com> User-Agent: Alpine 2.22 (LSU 394 2020-01-19) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Spam-Status: No, score=-4.9 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,KAM_SHORT,SPF_HELO_NONE,SPF_PASS,TXREP,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On Fri, 9 Jun 2023, Jiufu Guo wrote: > > Hi, > > Richard Biener writes: > > > On Fri, 9 Jun 2023, Jiufu Guo wrote: > > > >> > >> Hi, > >> > >> Richard Biener writes: > >> > >> > On Fri, 9 Jun 2023, Richard Sandiford wrote: > >> > > >> >> guojiufu writes: > >> >> > Hi, > >> >> > > >> >> > On 2023-06-09 16:00, Richard Biener wrote: > >> >> >> On Fri, 9 Jun 2023, Jiufu Guo wrote: > >> >> >> > >> >> >>> Hi, > >> >> >>> > ... > >> >> >>> > >> >> >>> This patch is raised when drafting below one. > >> >> >>> https://gcc.gnu.org/pipermail/gcc-patches/2022-October/603530.html. > >> >> >>> With that patch, "{[%1:DI]=0;} stack_tie" with BLKmode runs into > >> >> >>> try_const_anchors, and hits the assert/ice. > >> >> >>> > >> >> >>> Boostrap and regtest pass on ppc64{,le} and x86_64. > >> >> >>> Is this ok for trunk? > >> >> >> > >> >> >> Iff the correct fix at all (how can a CONST_INT have BLKmode?) then > >> >> >> I suggest to instead fix try_const_anchors to change > >> >> >> > >> >> >> /* CONST_INT is used for CC modes, but we should leave those alone. > >> >> >> */ > >> >> >> if (GET_MODE_CLASS (mode) == MODE_CC) > >> >> >> return NULL_RTX; > >> >> >> > >> >> >> gcc_assert (SCALAR_INT_MODE_P (mode)); > >> >> >> > >> >> >> to > >> >> >> > >> >> >> /* CONST_INT is used for CC modes, leave any non-scalar-int mode > >> >> >> alone. */ > >> >> >> if (!SCALAR_INT_MODE_P (mode)) > >> >> >> return NULL_RTX; > >> >> >> > >> >> > > >> >> > This is also able to fix this issue. there is a "Punt on CC modes" > >> >> > patch > >> >> > to return NULL_RTX in try_const_anchors. > >> >> > > >> >> >> but as said I wonder how we arrive at a BLKmode CONST_INT and whether > >> >> >> we should have fended this off earlier. Can you share more complete > >> >> >> RTL of that stack_tie? > >> >> > > >> >> > > >> >> > (insn 15 14 16 3 (parallel [ > >> >> > (set (mem/c:BLK (reg/f:DI 1 1) [1 A8]) > >> >> > (const_int 0 [0])) > >> >> > ]) "/home/guojiufu/temp/gdb.c":13:3 922 {stack_tie} > >> >> > (nil)) > >> >> > > >> >> > It is "set (mem/c:BLK (reg/f:DI 1 1) (const_int 0 [0])". > >> >> > >> >> I'm not convinced this is correct RTL. (unspec:BLK [(const_int 0)] ...) > >> >> would be though. It's arguably more accurate too, since the effect > >> >> on the stack locations is unspecified rather than predictable. > >> > > >> > powerpc seems to be the only port with a stack_tie that's not > >> > using an UNSPEC RHS. > >> In rs6000.md, it is > >> > >> ; This is to explain that changes to the stack pointer should > >> ; not be moved over loads from or stores to stack memory. > >> (define_insn "stack_tie" > >> [(match_parallel 0 "tie_operand" > >> [(set (mem:BLK (reg 1)) (const_int 0))])] > >> "" > >> "" > >> [(set_attr "length" "0")]) > >> > >> This would be just an placeholder insn, and acts as the comments. > >> UNSPEC_ would works like other targets. While, I'm wondering > >> the concerns on "set (mem:BLK (reg 1)) (const_int 0)". > >> MODEs between SET_DEST and SET_SRC? > > > > I don't think the issue is the mode but the issue is that > > the patter as-is says some memory is zeroed while that's not > > actually true (not specifying a size means we can't really do > > anything with this MEM, but still). Using an UNSPEC avoids > > implying anything for the stored value. > > > > Of course I think a MEM SET_DEST without a specified size is bougs > > as well, but there's larger precedent for this... > > Thanks for your kindly comments! > Using "(set (mem:BLK (reg 1)) (const_int 0))" here, may because this > insn does not generate real thing (not a real store and no asm code), > may like barrier. > > While I agree that, using UNSPEC may be more clear to avoid mis-reading. Btw, another way to avoid the issue in CSE is to make it not process (aka record anything for optimization) for SET from MEMs with !MEM_SIZE_KNOWN_P Richard.