From: "Francesco R." <vivo75@gmail.com>
To: gentoo-dev@lists.gentoo.org
Subject: Re: [gentoo-dev] New global use flags: 3dnowext, mmxext, ssse3, sse4_1, avx, avx2
Date: Mon, 16 Dec 2013 02:13:28 +0100 [thread overview]
Message-ID: <52AE53B8.6070809@gmail.com> (raw)
In-Reply-To: <CAEdQ38F31ZJvwEZKV+Y4w+yuhTmUvUAf7Ecjo5CvP06yg2tvwQ@mail.gmail.com>
Il 16/12/2013 01:30, Matt Turner ha scritto:
> On Sun, Dec 15, 2013 at 4:20 PM, Andreas K. Huettel
> <dilfridge@gentoo.org> wrote:
>> Am Montag, 16. Dezember 2013, 00:34:13 schrieb Matt Turner:
>>> 3dnow: Use the 3DNow! instruction set
>>> 3dnowext: Use the Enhanced 3DNow! instruction set
>>> mmx: Use the MMX instruction set
>>> mmxext: Use the Extended MMX instruction set (intersection of Enhanced
>>> 3DNow! and SSE instruction sets) (3dnowext or sse in cpuinfo)
>>> sse: Use the SSE instruction set
>>> sse2: Use the SSE2 instruction set
>>> sse3: Use the SSE3 instruction set (pni in cpuinfo)
>>> ssse3: Use the SSSE3 instruction set
>>> sse4_1: Use the SSE 4.1 instruction set
>>> avx: Use the AVX instruction set
>>> avx2: Use the AVX2 instruction set
>> What's the point of these flags?
>> (or to be more precise, are they really justified whenever they are used?)
>>
>> Usually the set of cpu instructions should be controlled by your CFLAGS, and
>> I've been actively patching packages (that do not do manually coded assembly)
>> to make such flags unnecessary.
> Often they're for enabling assembly code that uses these instruction
> sets. For pixman, a package that I'm very familiar with, they turn on
> code using these instruction sets using intrinsics in C. I believe
> they are justified.
>
> If the package simply uses the flag to add an -m<isa> flag to CFLAGS,
> then we should definitely remove it. If I recall correctly, I have
> only seen one instance of this.
>
another possible case are packages that do run-time checking of usable
instruction set.
The use flag could restrict the code to be compiled and installed from
the ebuild.
Probably never used like this tough
next prev parent reply other threads:[~2013-12-16 1:13 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-15 23:34 [gentoo-dev] New global use flags: 3dnowext, mmxext, ssse3, sse4_1, avx, avx2 Matt Turner
2013-12-16 0:20 ` Andreas K. Huettel
2013-12-16 0:30 ` Matt Turner
2013-12-16 1:13 ` Francesco R. [this message]
2013-12-16 12:07 ` Jeroen Roovers
2013-12-16 23:07 ` Rick "Zero_Chaos" Farina
2013-12-18 17:48 ` Jeroen Roovers
2013-12-16 10:44 ` [gentoo-dev] " Duncan
2013-12-16 15:38 ` Michael Orlitzky
2013-12-16 18:21 ` Alan McKinnon
2013-12-16 20:17 ` Michael Orlitzky
2013-12-16 20:48 ` Alan McKinnon
2013-12-18 18:49 ` Matt Turner
2013-12-19 12:11 ` [gentoo-dev] " Jan Matejka
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