From: Xi Ruoyao <xry111@mengyan1223.wang>
To: NightStrike <nightstrike@gmail.com>,
Jonathan Wakely <jwakely.gcc@gmail.com>
Cc: gcc-help <gcc-help@gcc.gnu.org>, unlvsur unlvsur <unlvsur@live.com>
Subject: Re: how to get -march=native's value?
Date: Fri, 17 Sep 2021 16:29:17 +0800 [thread overview]
Message-ID: <5b4a11b1a9a3945256d298cd355991dcffa1d806.camel@mengyan1223.wang> (raw)
In-Reply-To: <CAF1jjLvPXz-Wfc5F2e0-5VhefpPPD1oY1H+2YvTy6sc5e8oxkg@mail.gmail.com>
On Thu, 2021-09-16 at 22:46 -0400, NightStrike via Gcc-help wrote:
> On Tue, Sep 7, 2021 at 3:57 AM Jonathan Wakely via Gcc-help
> <gcc-help@gcc.gnu.org> wrote:
> >
> > On Tue, 7 Sep 2021, 08:03 unlvsur unlvsur via Gcc-help, <
> > gcc-help@gcc.gnu.org> wrote:
> >
> > > I try to cross compile to another slower machine. -march=native
> > > works on
> > > that architectures, but I would like to know what is the value of
> > > -march=??? For -march=native. Is there a way to print march value
> > > out??
> > >
> >
> > It doesn't choose a single value. It enables all the individual
> > options
> > like -msse and that combination of options might not correspond to any
> > particular -march value.
>
> Is that true? I mean, in principle, I know I've reported a bug where
> -march=native scanned /proc/cpuinfo (or however it got the info) and
> came up with a different result than -march=k8 (or whatever I was
> reporting at the time), but that was a bug that some helpful people
> fixed. If gcc doesn't have an -march for a particular esoteric arch,
> then fine, but if it does, I'd think that this would be a bug similar
> to what I experienced previously.
It's documented clearly:
native
This selects the CPU to generate code for at compilation time
by determining the processor type of the compiling machine.
Using -march=native enables all instruction subsets supported
by the local machine (hence the result might not run on
different machines). Using -mtune=native produces code
optimized for the local machine under the constraints of the
selected instruction set.
However if it produce something can't run on your machine,
this is a bug.
--
Xi Ruoyao <xry111@mengyan1223.wang>
School of Aerospace Science and Technology, Xidian University
next prev parent reply other threads:[~2021-09-17 8:29 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-07 7:02 unlvsur unlvsur
2021-09-07 7:56 ` Jonathan Wakely
2021-09-17 2:46 ` NightStrike
2021-09-17 8:29 ` Xi Ruoyao [this message]
2021-09-17 10:26 ` Jonathan Wakely
2021-09-17 10:38 ` Jonathan Wakely
2021-09-17 17:53 ` Segher Boessenkool
2021-09-27 12:55 ` Vincent Lefevre
2021-09-27 17:13 ` Segher Boessenkool
2021-09-27 18:14 ` L A Walsh
2021-09-27 18:25 ` Jonathan Wakely
2021-09-27 20:26 ` Segher Boessenkool
2021-09-27 20:30 ` NightStrike
2021-09-27 18:26 ` Florian Weimer
2021-09-07 7:59 ` Hongtao Liu
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