From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 122184 invoked by alias); 12 Sep 2017 14:16:51 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Received: (qmail 122174 invoked by uid 89); 12 Sep 2017 14:16:51 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.1 required=5.0 tests=AWL,BAYES_00,KAM_LAZY_DOMAIN_SECURITY,RCVD_IN_DNSWL_LOW autolearn=no version=3.3.2 spammy=coherent X-HELO: mx0a-001b2d01.pphosted.com Subject: Re: [PATCH] powerpc: Use aligned stores in memset From: Steven Munroe Reply-To: munroesj@linux.vnet.ibm.com To: Florian Weimer Cc: Rajalakshmi Srinivasaraghavan , libc-alpha@sourceware.org In-Reply-To: <87wp54vwk4.fsf@mid.deneb.enyo.de> References: <1503033107-20047-1-git-send-email-raji@linux.vnet.ibm.com> <1505223476.12360.14.camel@oc7878010663> <87wp54vwk4.fsf@mid.deneb.enyo.de> Content-Type: text/plain; charset="UTF-8" Date: Tue, 12 Sep 2017 14:16:00 -0000 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 17091214-0004-0000-0000-000012E9458B X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007711; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000227; SDB=6.00915969; UDB=6.00459919; IPR=6.00696200; BA=6.00005587; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00017126; XFM=3.00000015; UTC=2017-09-12 14:16:43 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17091214-0005-0000-0000-0000840F3DC7 Message-Id: <1505225800.12360.28.camel@oc7878010663> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-09-12_04:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1707230000 definitions=main-1709120200 X-SW-Source: 2017-09/txt/msg00499.txt.bz2 On Tue, 2017-09-12 at 16:08 +0200, Florian Weimer wrote: > * Steven Munroe: > > >> This means that GCC introduced an unaligned store, no matter how memset > >> was implemented. > >> > > C will do what ever the programmer wants. We can not stop that. > > That's not true. If some specification says that for POWER, mem* must > behave in a certain way, and the GCC/glibc combiniation does not do > that, that's a bug on POWER. > What is the bug that you think we are not fixing? > The programmer only sees the entire toolchain, and it is our job to > make the whole thing compliant with applicable specifications, even if > this means coordinating among different projects. > > > And in user mode and cache coherent memory this is not a problem as > > Adhemerval explained. > > Obviously not, otherwise we wouldn't be changing glibc. > I was arguing against forcing GCC and compilers in general being forced to be aware of Cache Inhibited memory. Programmers do. What are you arguing? > > So we are not going to degrade the performance of general applications > > for a tiny subset of specialized device drivers. Those guy have to know > > what they are doing. > > > > But in the library (like libc) that might be called from a user mode > > device driver (Xorg for example) and access Cache inhibited memory the > > memcpy implementation has to check alignment and size and using the > > correct instructions for each case. > > > > That is what we are doing here. > > Sorry, but you are contradicting yourself. I very much doubt the > Xorg-compatible memcmp is an improvement across the board. >