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 [63.128.21.124]) by sourceware.org (Postfix) with ESMTP id 76D603850423 for ; Mon, 8 Feb 2021 10:55:47 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 76D603850423 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-454-cKk3GLmyMqymk3xBxyg3yA-1; Mon, 08 Feb 2021 05:55:45 -0500 X-MC-Unique: cKk3GLmyMqymk3xBxyg3yA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 6AEE3801962; Mon, 8 Feb 2021 10:55:44 +0000 (UTC) Received: from tucnak.zalov.cz (ovpn-112-197.ams2.redhat.com [10.36.112.197]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 00F2C5D9DD; Mon, 8 Feb 2021 10:55:43 +0000 (UTC) Received: from tucnak.zalov.cz (localhost [127.0.0.1]) by tucnak.zalov.cz (8.16.1/8.16.1) with ESMTPS id 118AteCu1143809 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Mon, 8 Feb 2021 11:55:41 +0100 Received: (from jakub@localhost) by tucnak.zalov.cz (8.16.1/8.16.1/Submit) id 118AteJD1143808; Mon, 8 Feb 2021 11:55:40 +0100 Date: Mon, 8 Feb 2021 11:55:40 +0100 From: Jakub Jelinek To: Richard Biener Cc: Naoki Shibata , GCC Development Subject: Re: Calls to auto-vectorized AVX512 functions Message-ID: <20210208105540.GM4020736@tucnak> Reply-To: Jakub Jelinek References: <03eaf35c-7c29-468d-5939-d2a6b530e221@gmail.com> MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Spam-Status: No, score=-6.5 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H4, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: gcc@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 08 Feb 2021 10:55:49 -0000 On Mon, Feb 08, 2021 at 11:42:13AM +0100, Richard Biener via Gcc wrote: > > I have a question as to the auto-vectorizer in GCC. > > > > When AVX512 instruction is available, the auto-vectorizer in gcc > > sometimes generates calls to AVX2 functions instead of AVX512 functions. > > > > > > $ cat vabitest.c > > #include > > #include > > > > _Pragma ("omp declare simd simdlen(8) notinbranch") > > __attribute__((const)) double myfunc(double x); > > > > #define N 1024 > > __attribute__ ((__aligned__(256))) double a[N], b[N], c[N]; > > > > int main(void) { > > for (int i = 0; i < N; i++) a[i] = myfunc(b[i]); > > for (int i = 0; i < N; i++) c[i] = sin(b[i]); > > } > > > > $ gcc-10 -ffast-math -O3 -mavx512f -fopenmp vabitest.c -S -o- | grep _ZGV > > call _ZGVdN8v_myfunc@PLT > > call _ZGVeN8v_sin@PLT > > > > > > Is there a way to force gcc to generate calls to AVX512 function in > > cases like this? > > Not sure, the sin function get's called with a %zmm argument but > myfunc is called with two %ymm arguments but returns a %zmm. > Something seems messed up somewhere. > > Can you open a bugreport? I'd guess it is -mprefer-vector-width=256 by default, though it surprises me %zmm is used for sin. In any case, I'd retry with mprefer-vector-width=512. Jakub