From: Jonathan Wakely <jwakely.gcc@gmail.com>
To: Tom Kacvinsky <tkacvins@gmail.com>
Cc: Andrew Haley <aph@redhat.com>, gcc-help <gcc-help@gcc.gnu.org>
Subject: Re: -march=x86_64 -mtune=generic question
Date: Thu, 26 May 2022 12:05:27 +0100 [thread overview]
Message-ID: <CAH6eHdTQmEfAOVSmH-zFOVOydhVUBrF8ArCP_VPqU5TCc_WHxA@mail.gmail.com> (raw)
In-Reply-To: <CAG_eJLd3hPam3GHXA+7Maj1McNW=JoMMC9PaW2+sCn5OL063sQ@mail.gmail.com>
On Thu, 26 May 2022 at 11:15, Tom Kacvinsky via Gcc-help
<gcc-help@gcc.gnu.org> wrote:
> A colleague of mine reminded me of this thread:
>
> slowdown with -std=gnu18 with respect to -std=c99
>
> So I checked what the default C standard for GCC 8.3.0 is (gnu11) and 12.1.0
> (gnu17). So I used -std=c99 with the GCC 12.1 build of our code, and things
> went back to normal (and sometimes a teensy bit better).
N.B. the issue in that thread was the difference between -std=cNN and
-std=gnuNN, not the changes in the value of NN.
So you should be able to use -std=c17 and get the same performance as -std=c99.
prev parent reply other threads:[~2022-05-26 11:05 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-25 18:58 Tom Kacvinsky
2022-05-26 7:11 ` Andrew Haley
2022-05-26 10:13 ` Tom Kacvinsky
2022-05-26 11:05 ` Jonathan Wakely [this message]
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