Date: Wed, 25 Oct 2017 21:54:22 +0200
From: Natanael Copa <ncopa@alpinelinux.org>
To: "A. Wilcox" <awilfox@adelielinux.org>
Cc: alpine-devel@lists.alpinelinux.org
Subject: Re: [alpine-devel] force compile flag for musl?
Message-ID: <20171025215422.3c9ddcfd@ncopa-desktop.copa.dup.pw>
In-Reply-To: <59F0E348.6020807@adelielinux.org>
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	<59F0E348.6020807@adelielinux.org>
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On Wed, 25 Oct 2017 14:17:28 -0500
"A. Wilcox" <awilfox@adelielinux.org> wrote:

> On 25/10/17 09:46, Natanael Copa wrote:
> > Hi,
> >=20
> >=20
> > I wonder what you think about overriding the -Os compile flag for=20
> > musl, and hardcode it to -O2. =20
>=20
>=20
> Possibly.  Is there some benchmarks available, maybe using libc-test
> or such?
>=20
>=20
> > What do you think?
> >=20
> > +       # force -O2 compile flag for better performance +
> > CFLAGS=3D"-O2" \ =20
>=20
>=20
> No.  Stuff in abuild.conf needs to be preserved and -O2 tacked on the
> end (GCC will only honour last -O flag passed, so this is what you want).
>=20
> This is INCREDIBLY important to us at Ad=E9lie because for instance
> ppc64 BE requires -fno-inline-small-functions due to GCC bug elsewise
> it will cause ABI issues with long double.  We also use -march / -mcpu
> which would be discarded here as well, which would cause it to be
> slower on some platforms (-O2 won't help as much on x86_32 as it would
> on -march=3Dpentium4 x86_32, for instance).

Thanks. This is useful information.
=20
> I agree with the idea of using -O2 but not with the implementation of
> blowing away all other CFLAGS.

I was thinking about this, yes. I think something like:

  CFLAGS=3D"$CFLAGS -O2"

would be better. Alternatively we could have an optional performance opt, s=
omething like:

  CFLAGS=3D"${CFLAGS_OPT_PERFORMACE:-$CFLAGS}"

But I think we just keep it simple as it is, because I measured it and
-O2 was actually slightly slower for the specific use case.

Thanks!

-nc

>=20
> Best,
> --arw
>=20



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