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From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Oleksandr Natalenko <oleksandr@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] Kconfig: default to CC_OPTIMIZE_FOR_PERFORMANCE_O3 for gcc >= 10
Date: Fri, 8 May 2020 06:07:02 -0600	[thread overview]
Message-ID: <CAHmME9p7Hri-vHfwR9GY1gPo91jVx4-hTqsZVRHiioUENRHibA@mail.gmail.com> (raw)
In-Reply-To: <CAK8P3a0dJ0vNnktcoWFiPKB4NJbeyf7nvwWf0YLyeUyxT5pvQg@mail.gmail.com>

On Fri, May 8, 2020 at 5:56 AM Arnd Bergmann <arnd@arndb.de> wrote:
>
> On Fri, May 8, 2020 at 1:33 PM Oleksandr Natalenko <oleksandr@redhat.com> wrote:
> >
> > On Fri, May 08, 2020 at 05:21:47AM -0600, Jason A. Donenfeld wrote:
> > > > Should we untangle -O3 from depending on ARC first maybe?
> > >
> > > Oh, hah, good point. Yes, I'll do that for a v2, but will wait another
> > > day for feedback first.
> >
> > Just keep in mind that my previous attempt [1] failed because of too
> > many false positive warnings despite -O3 really uncovered a couple of
> > bugs in the codebase.
>
> I think my warning fixes were mostly picked up in the meantime, but
> if there are any remaining, they would be mixed in with random other
> fixes in my testing tree, so it's hard to know for sure.
>
> I also want to hear the feedback from the gcc developers about what
> the general recommendations are between O2 and O3, and how
> they may have changed over time. According to the gcc-10 documentation,
> the difference between -O2 and -O3 is exactly this set of options:
>
> -fgcse-after-reload
> -fipa-cp-clone
> -floop-interchange
> -floop-unroll-and-jam
> -fpeel-loops
> -fpredictive-commoning
> -fsplit-loops
> -fsplit-paths
> -ftree-loop-distribution
> -ftree-loop-vectorize
> -ftree-partial-pre
> -ftree-slp-vectorize
> -funswitch-loops
> -fvect-cost-model
> -fvect-cost-model=dynamic
> -fversion-loops-for-strides

The other significant thing -- and what prompted this patchset -- is
it looks like gcc 10 has lowered the inlining degree for -O2, and put
gcc 9's inlining parameters from -O2 into gcc-10's -O3.

  reply	other threads:[~2020-05-08 12:07 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-07 22:45 Jason A. Donenfeld
2020-05-08  8:35 ` Peter Zijlstra
2020-05-08  9:02 ` Oleksandr Natalenko
2020-05-08 11:21   ` Jason A. Donenfeld
2020-05-08 11:33     ` Oleksandr Natalenko
2020-05-08 11:49       ` Arnd Bergmann
2020-05-08 12:07         ` Jason A. Donenfeld [this message]
2020-05-08 13:04           ` Arnd Bergmann
2020-05-08 15:06         ` Joe Perches
2020-05-08 15:09           ` Arnd Bergmann
2020-05-10 12:47           ` David Laight
2020-05-10 17:45             ` Joe Perches
2020-05-10 18:58               ` David Laight
2020-05-12  1:10             ` Masahiro Yamada
2020-05-11 21:57   ` [PATCH v2] " Jason A. Donenfeld
2020-05-12  0:04     ` Linus Torvalds
2020-05-12  0:09       ` Linus Torvalds
2020-05-12  0:43       ` Jason A. Donenfeld
2020-05-12  8:44       ` Richard Biener
2020-05-13 11:27 ` [PATCH] " Artem S. Tashkinov

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