From: "H.J. Lu" <hjl.tools@gmail.com>
To: Mark Wielaard <mark@klomp.org>
Cc: Florian Weimer <fweimer@redhat.com>,
GNU C Library <libc-alpha@sourceware.org>,
GCC Development <gcc@gcc.gnu.org>,
llvm-dev@lists.llvm.org,
x86-64-abi <x86-64-abi@googlegroups.com>,
"Mallappa, Premachandra" <Premachandra.Mallappa@amd.com>,
Michael Matz <matz@suse.de>, Tom Stellard <tstellar@redhat.com>,
Jeff Law <law@redhat.com>
Subject: Re: New x86-64 micro-architecture levels
Date: Wed, 15 Jul 2020 07:45:28 -0700 [thread overview]
Message-ID: <CAMe9rOq+SbMLM9H4U9spO_4OK0P-=vP-3YapPM3o8vo5QbvDjA@mail.gmail.com> (raw)
In-Reply-To: <ae608575d0b2d70dc8b6c06d49efe94edd4c7350.camel@klomp.org>
On Wed, Jul 15, 2020 at 7:38 AM Mark Wielaard <mark@klomp.org> wrote:
>
> Hi Florian,
>
> I understand you want to discuss the x86_64 micro-architecture levels
> only in this thread, but it would be nice to have a similar discussion
> for other architectures.
>
> One thing that wasn't clear to me from this proposal is how the glibc
> dynamic loader checks for the CPU feature flags. This is important for
> valgrind since it can communicate those through different means. cpuid
> interception, auxv AT_HWCAP/AT_HWCAP2 interception (but not AT_PLATFORM
> at the moment) and of course we can generate SIGILL for unsupported
> instructions. We currently don't intercept /proc/cpuinfo (but could).
In library, we can use <sys/platform/x86.h>:
https://sourceware.org/pipermail/libc-alpha/2020-June/115546.html
In GCC, we can use __builtin_cpu_supports.
<sys/platform/x86.h> supports all features and __builtin_cpu_supports in
GCC 11 supports all features which GCC has codegen for.
> I think it is important to be precise here, because in the past this
> has sometimes caused confusion. For example for how to check correctly
> for avx, lzcnt, or fma[4] support.
>
> Thanks,
>
> Mark
>
> P.S. I don't particular like the numbered names, but well, bike-shed...
--
H.J.
next prev parent reply other threads:[~2020-07-15 14:46 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-10 17:30 Florian Weimer
2020-07-10 19:14 ` Joseph Myers
2020-07-13 7:55 ` Florian Weimer
2020-07-10 21:42 ` H.J. Lu
2020-07-13 6:23 ` Richard Biener
2020-07-13 7:40 ` Florian Weimer
2020-07-13 7:47 ` Jan Beulich
2020-07-13 13:31 ` H.J. Lu
2020-07-13 13:53 ` Jakub Jelinek
2020-07-13 8:57 ` Richard Biener
2020-07-13 6:49 ` Florian Weimer
2020-07-13 13:30 ` H.J. Lu
2020-07-11 7:40 ` Allan Sandfeld Jensen
2020-07-13 6:58 ` Florian Weimer
2020-07-15 14:38 ` Mark Wielaard
2020-07-15 14:45 ` H.J. Lu [this message]
2020-07-15 14:56 ` Florian Weimer
2020-07-21 16:05 ` Mallappa, Premachandra
2020-07-21 18:04 ` Florian Weimer
2020-07-22 1:31 ` Dongsheng Song
2020-07-22 8:44 ` Florian Weimer
2020-07-22 9:26 ` Richard Biener
2020-07-22 10:16 ` Florian Weimer
2020-07-22 13:50 ` Richard Biener
2020-07-22 14:21 ` H.J. Lu
2020-07-31 13:06 ` Carlos O'Donell
2020-07-22 7:48 ` Jan Beulich
2020-07-22 10:34 ` Florian Weimer
2020-07-22 11:41 ` Jan Beulich
2020-07-31 13:20 ` Carlos O'Donell
2020-07-22 16:45 ` Mallappa, Premachandra
2020-07-23 12:44 ` Michael Matz
2020-07-23 13:21 ` H.J. Lu
2020-07-28 15:54 ` Florian Weimer
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