From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id 573C2395BC5F for ; Fri, 13 May 2022 12:55:33 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 573C2395BC5F Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-193-30LwZak4MA6QO96XioogOg-1; Fri, 13 May 2022 08:55:30 -0400 X-MC-Unique: 30LwZak4MA6QO96XioogOg-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id B0E38185A7BA; Fri, 13 May 2022 12:55:29 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.192.147]) by smtp.corp.redhat.com (Postfix) with ESMTPS id AA3F2C27E84; Fri, 13 May 2022 12:55:28 +0000 (UTC) From: Florian Weimer To: Siddhesh Poyarekar Cc: libc-alpha@sourceware.org, dickey@his.com Subject: Re: [PATCH v3] wcrtomb: Make behavior POSIX compliant References: <20220505184348.3357550-3-siddhesh@sourceware.org> <20220512131503.764504-1-siddhesh@sourceware.org> <4ffe566a-8002-b574-daee-d6927b8ceaef@cs.ucla.edu> <02979241-ff47-ef76-0c77-268aca00c4b8@sourceware.org> <87ilq9d5n2.fsf@oldenburg.str.redhat.com> <07456c63-a1e9-2a1e-bdb1-1f1c438992e0@sourceware.org> Date: Fri, 13 May 2022 14:55:26 +0200 In-Reply-To: <07456c63-a1e9-2a1e-bdb1-1f1c438992e0@sourceware.org> (Siddhesh Poyarekar's message of "Fri, 13 May 2022 17:21:48 +0530") Message-ID: <875ym9d22p.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.85 on 10.11.54.8 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-3.6 required=5.0 tests=BAYES_00, BODY_8BITS, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_LOW, SPF_HELO_NONE, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 13 May 2022 12:55:34 -0000 * Siddhesh Poyarekar: > On 13/05/2022 17:08, Florian Weimer via Libc-alpha wrote: >> * Siddhesh Poyarekar: >>=20 >>> On 13/05/2022 10:58, Paul Eggert wrote: >>>> On 5/12/22 21:56, Paul Eggert wrote: >>>>> Hope you don't mind my bikeshedding. >>>> Better yet, this: >>>> =C2=A0 s[0] =3D buf[0]; >>>> =C2=A0 if (2 <=3D result && result <=3D 4) >>>> =C2=A0=C2=A0=C2=A0 { >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 s[1] =3D buf[1]; >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 memcpy (&s[result - 2], &buf[result -= 2], 2); >>>> =C2=A0=C2=A0=C2=A0 } >>>> =C2=A0 else >>>> =C2=A0=C2=A0=C2=A0 memcpy (s, buf, result); >>>> On x86-64 with GCC 12.1 -O2 and a glibc-supplied charmap, this is >>>> only 9 straight-line instructions, counting the compare insn and the >>>> conditional-branch insn that is never taken. >>>> >>> >>> Sorry I missed this one. I tried it and with gcc 11 it seems to >>> produce worse code, merging the two memcpys instead of inlining the >>> first one. >> Can we please use the simplified code? > > So just a memcpy call? I could push that and attempt to > micro-optimize if there are reports of slowdown due to this. Yes, I would prefer that. Thanks, Florian