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Re: [PATCH x86_64][BZ #20139] Don't allow configure with not supporting AVX512 assembler w/o --disable-avx512.
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: Andrew Senkevich <andrew dot n dot senkevich at gmail dot com>, libc-alpha <libc-alpha at sourceware dot org>
- Date: Mon, 27 Jun 2016 12:40:32 -0700
- Subject: Re: [PATCH x86_64][BZ #20139] Don't allow configure with not supporting AVX512 assembler w/o --disable-avx512.
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- References: <CAMXFM3tJkhW78PPe4=FUhbm=8HoOY4iouSqXxLObA0GEMTxoZA at mail dot gmail dot com> <20160627181631 dot GA4091 at vapier dot lan> <CAMe9rOqJsAQXJq767=zpLH=YFp0kixzDwLy8qJOB0qB-LaKL7g at mail dot gmail dot com> <20160627190450 dot GB4091 at vapier dot lan> <CAMe9rOozsdKcsfLbPn2oZQVPTDJD5H4_-1vik9AWdUWR+LjQFA at mail dot gmail dot com> <20160627191755 dot GD4091 at vapier dot lan>
On Mon, Jun 27, 2016 at 12:17 PM, Mike Frysinger <vapier@gentoo.org> wrote:
> On 27 Jun 2016 12:09, H.J. Lu wrote:
>> On Mon, Jun 27, 2016 at 12:04 PM, Mike Frysinger <vapier@gentoo.org> wrote:
>> > On 27 Jun 2016 11:25, H.J. Lu wrote:
>> >> On Mon, Jun 27, 2016 at 11:16 AM, Mike Frysinger <vapier@gentoo.org> wrote:
>> >> > On 27 Jun 2016 20:40, Andrew Senkevich wrote:
>> >> >> +'--disable-avx512'
>> >> >> + By default for x86_64, the GNU C Library is built with
>> >> >> + '--enable-avx512'. Configure with '--disable-avx512' if assembler
>> >> >> + doesn't support AVX512.
>> >> >
>> >> > people shouldn't have to pass configure flags like this to get a
>> >> > successful build. we have all the info in order to figure out a
>> >> > sane default. specifying enable/disable flags is purely to not
>> >> > use the default autodetection.
>> >>
>> >> We want to make sure that x86-64 glibc supports AVX512. Any
>> >> suggestions are welcome.
>> >
>> > i don't see how that's relevant to what i said. if the assembler can
>> > be probed to see if it supports AVX512, then do that. why do you need
>> > a configure flag at all in that case ?
>>
>> We want to REQUIRE AVX512 support for x86-64 glibc build.
>
> then why are you adding a configure flag ? why is AVX512 special
> compared to any other ISA feature ? if the majority of people are
> getting their builds from distros, is a flag really needed ?
See
https://sourceware.org/ml/libc-alpha/2016-06/msg01061.html
--
H.J.