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 78E7C3858C2C for ; Mon, 27 Sep 2021 20:27:34 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 78E7C3858C2C 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 18RKQXdZ029289; Mon, 27 Sep 2021 15:26:33 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 18RKQWT8029286; Mon, 27 Sep 2021 15:26:32 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Mon, 27 Sep 2021 15:26:32 -0500 From: Segher Boessenkool To: Jonathan Wakely Cc: L A Walsh , gcc-help , unlvsur unlvsur Subject: Re: how to get -march=native's value? Message-ID: <20210927202632.GB8185@gate.crashing.org> References: <5b4a11b1a9a3945256d298cd355991dcffa1d806.camel@mengyan1223.wang> <20210917175325.GS1583@gate.crashing.org> <20210927125528.GA3789484@cventin.lip.ens-lyon.fr> <20210927171344.GA8185@gate.crashing.org> <61520A1E.9050900@tlinx.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i X-Spam-Status: No, score=-3.4 required=5.0 tests=BAYES_00, JMQ_SPF_NEUTRAL, KAM_DMARC_STATUS, SPF_HELO_PASS, SPF_PASS, TXREP autolearn=no autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: gcc-help@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-help mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 27 Sep 2021 20:27:36 -0000 On Mon, Sep 27, 2021 at 07:25:58PM +0100, Jonathan Wakely wrote: > On Mon, 27 Sept 2021 at 19:16, L A Walsh wrote: > > On 2021/09/27 10:13, Segher Boessenkool wrote: > > > On Mon, Sep 27, 2021 at 02:55:28PM +0200, Vincent Lefevre wrote: > > >> On 2021-09-17 12:53:25 -0500, Segher Boessenkool wrote: > > >> > > >>> For x86 -march=something is the same as -march=native, _if_ the compiler > > >>> knows about your CPU. > > >>> > > ---- > > I have a question, as someone reading this conversation .... > > > > If one is using cross-compilation -- as it sounded like the original > > author might be doing, what could the compiler know about the target > > machine? > > Only what you tell it. > > > Is there some sort of "profile-this-cpu-for-pertinent-options" binary > > or compiler-option that one should(or could) run on the target > > machine in order that the correct compiler switches be set? > > > > Otherwise, it would seem that -march=native would only be useful for > > the (probably majority of) cases where one is compiling for their own > > machine (?). > > Yes, -march=native is for native compilation, not cross compilation. > The clue is in the name :-) And in fact you get something like $ x86_64-linux-gcc-12.0.0 -Wall -W -O2 -S at.c -march=native cc1: error: bad value ('native') for '-march=' switch cc1: note: valid arguments to '-march=' switch are: nocona core2 nehalem corei7 westmere sandybridge corei7-avx ivybridge core-avx-i haswell core-avx2 broadwell skylake skylake-avx512 cannonlake icelake-client rocketlake icelake-server cascadelake tigerlake cooperlake sapphirerapids alderlake bonnell atom silvermont slm goldmont goldmont-plus tremont knl knm x86-64 x86-64-v2 x86-64-v3 x86-64-v4 eden-x2 nano nano-1000 nano-2000 nano-3000 nano-x2 eden-x4 nano-x4 k8 k8-sse3 opteron opteron-sse3 athlon64 athlon64-sse3 athlon-fx amdfam10 barcelona bdver1 bdver2 bdver3 bdver4 znver1 znver2 znver3 btver1 btver2 when you try. Not the friendliest error message perhaps, but it is a pretty silly thing to try as well :-) (This has been the same since at least 5.4.1 (but the note is newer)). Segher