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Date: Fri, 9 Oct 2020 10:27:56 +0100
From: Ashley Dixon <ash@suugaku.co.uk>
To: gentoo-user@lists.gentoo.org
Subject: Re: [gentoo-user] Re: Multilib ABI specific CPU use flags?
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On Fri, Oct 09, 2020 at 12:26:17AM +0000, Jonathan Yong wrote:
> I'm open to fixing ebuild packages by myself in my own overlay, though I
> prefer not to due to eventual bit rot. Any hints on how to mask CPU USE
> flags based on multilib arch in the .ebuild file itself?
I suppose you could detect whether a CPU_FLAG is enabled for a x86_32 mult=
ilib,
although be wary that `MULTILIB_ABI_FLAG` is only exported for some mul=
tilib
functions, such as `multilib_src_configure` [1]:
if [[ ${MULTILIB_ABI_FLAG} =3D=3D abi_x86_32 ]] && use cpu_flags_x8=
6_avx2;
then
ewarn "Disabling AVX2 extensions for 32-bit build."
# circumvention measures
fi
I'm not sure of the best way to achieve the "circumvention measures", hence=
the
comment. You could run this conditional after GLOBALCMAKEARGS has been =
set,
omitting the CPU_BASELINE definition in the main block [2], or you could=
sed
through the USE flags and disable `cpu_flags_x86_avx2` there. You're pro=
bably
better asking on IRC for the best-practice way to achieve this.
As mentioned in the relevant bug report, this is not an issue caused by=
the
ebuild, so although this might prove to be a temporary fix, it will hopeful=
ly be
resolved by upstream very soon. Just be patient. ;-)
[1] https://wiki.gentoo.org/wiki/Project:Multilib/multilib-build#MULTILIB_A=
BI_FLAG
[2] https://github.com/opencv/opencv/wiki/CPU-optimizations-build-options#c=
ustomizing-cmake-options
[3] https://bugs.gentoo.org/747163#c15
--=20
Ashley Dixon
suugaku.co.uk
2A9A 4117
DA96 D18A
8A7B B0D2
A30E BF25
F290 A8AA
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