From: "H.J. Lu" <hjl.tools@gmail.com>
To: GNU C Library <libc-alpha@sourceware.org>,
"Carlos O'Donell" <carlos@redhat.com>,
Florian Weimer <fweimer@redhat.com>
Subject: Re: PING^3: V8 [PATCH 2/2] x86: Install <sys/platform/x86.h> [BZ #26124]
Date: Thu, 10 Sep 2020 07:29:46 -0700 [thread overview]
Message-ID: <CAMe9rOqHfhKzYse-efaSrrMG-kg7p2KyaMQK=9a8zrA0uxYBqg@mail.gmail.com> (raw)
In-Reply-To: <CAMe9rOqu+V-EMXB80f=HrOSz+ZvxpNWO3+vAFmYbTxiKqNNQ4Q@mail.gmail.com>
On Mon, Sep 7, 2020 at 11:21 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Wed, Sep 2, 2020 at 5:55 AM H.J. Lu <hjl.tools@gmail.com> wrote:
> >
> > On Wed, Aug 19, 2020 at 5:52 AM H.J. Lu <hjl.tools@gmail.com> wrote:
> > >
> > > On Wed, Aug 12, 2020 at 7:00 AM H.J. Lu <hjl.tools@gmail.com> wrote:
> > > >
> > > > On Wed, Aug 5, 2020 at 4:01 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > > > >
> > > > > Install <sys/platform/x86.h> so that programmers can do
> > > > >
> > > > > #if __has_include(<sys/platform/x86.h>)
> > > > > #include <sys/platform/x86.h>
> > > > > #endif
> > > > > ...
> > > > >
> > > > > if (CPU_FEATURE_USABLE (SSE2))
> > > > > ...
> > > > > if (CPU_FEATURE_USABLE (AVX2))
> > > > > ...
> > > > >
> > > > > <sys/platform/x86.h> exports only:
> > > > >
> > > > > enum
> > > > > {
> > > > > COMMON_CPUID_INDEX_1 = 0,
> > > > > COMMON_CPUID_INDEX_7,
> > > > > COMMON_CPUID_INDEX_80000001,
> > > > > COMMON_CPUID_INDEX_D_ECX_1,
> > > > > COMMON_CPUID_INDEX_80000007,
> > > > > COMMON_CPUID_INDEX_80000008,
> > > > > COMMON_CPUID_INDEX_7_ECX_1,
> > > > > /* Keep the following line at the end. */
> > > > > COMMON_CPUID_INDEX_MAX
> > > > > };
> > > > >
> > > > > struct cpuid_features
> > > > > {
> > > > > struct cpuid_registers cpuid;
> > > > > struct cpuid_registers usable;
> > > > > };
> > > > >
> > > > > struct cpu_features
> > > > > {
> > > > > struct cpu_features_basic basic;
> > > > > struct cpuid_features features[COMMON_CPUID_INDEX_MAX];
> > > > > };
> > > > >
> > > > > /* Get a pointer to the CPU features structure. */
> > > > > extern const struct cpu_features *__x86_get_cpu_features
> > > > > (unsigned int max) __attribute__ ((const));
> > > > >
> > > > > Since all feature checks are done through macros, programs compiled with
> > > > > a newer <sys/platform/x86.h> are compatible with the older glibc binaries
> > > > > as long as the layout of struct cpu_features is identical. The features
> > > > > array can be expanded with backward binary compatibility for both .o and
> > > > > .so files. When COMMON_CPUID_INDEX_MAX is increased to support new
> > > > > processor features, __x86_get_cpu_features in the older glibc binaries
> > > > > returns NULL and HAS_CPU_FEATURE/CPU_FEATURE_USABLE return false on the
> > > > > new processor feature. No new symbol version is neeeded.
> > > > >
> > > > > Both CPU_FEATURE_USABLE and HAS_CPU_FEATURE are provided. HAS_CPU_FEATURE
> > > > > can be used to identify processor features.
> > > > >
> > > > > Note: Although GCC has __builtin_cpu_supports, it only supports a subset
> > > > > of <sys/platform/x86.h> and it is equivalent to CPU_FEATURE_USABLE. It
> > > > > doesn't support HAS_CPU_FEATURE.
> > >
> > > PING:
> > >
> > > https://sourceware.org/pipermail/libc-alpha/2020-August/116865.html
> > >
> >
> > If there are no more comments, I will check it next Friday,
> > Sept 11.
> >
>
> I am enclosing the rebased patch I am checking in this Friday.
>
I will check this in tomorrow:
https://sourceware.org/pipermail/libc-alpha/2020-September/117466.html
--
H.J.
prev parent reply other threads:[~2020-09-10 14:30 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-05 23:01 V8 [PATCH 1/2] x86: Clear some CPU usable feature bits H.J. Lu
2020-08-05 23:01 ` V8 [PATCH 2/2] x86: Install <sys/platform/x86.h> [BZ #26124] H.J. Lu
2020-08-12 14:00 ` PING: " H.J. Lu
2020-08-19 12:52 ` PING^2: " H.J. Lu
2020-09-02 12:55 ` PING^3: " H.J. Lu
2020-09-07 18:21 ` H.J. Lu
2020-09-10 14:29 ` H.J. Lu [this message]
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