diff mbox series

[v2,2/3] x86_64: Add glibc-hwcaps support

Message ID 54bcc4776d50207d54ca1eae32bdffaa6ffe3c01.1602515612.git.fweimer@redhat.com
State Superseded
Headers show
Series glibc-hwcaps support for LD_LIBRARY_PATH | expand

Commit Message

Florian Weimer Oct. 12, 2020, 3:21 p.m. UTC
The subdirectories match those in the x86-64 psABI:

https://gitlab.com/x86-psABIs/x86-64-ABI/-/commit/77566eb03bc6a326811cb7e9a6b9396884b67c7c
---
 sysdeps/x86_64/Makefile            | 36 +++++++++++++++-
 sysdeps/x86_64/dl-hwcaps-subdirs.c | 66 ++++++++++++++++++++++++++++++
 sysdeps/x86_64/tst-glibc-hwcaps.c  | 65 +++++++++++++++++++++++++++++
 3 files changed, 166 insertions(+), 1 deletion(-)
 create mode 100644 sysdeps/x86_64/dl-hwcaps-subdirs.c
 create mode 100644 sysdeps/x86_64/tst-glibc-hwcaps.c

Comments

H.J. Lu Oct. 12, 2020, 6:11 p.m. UTC | #1
On Mon, Oct 12, 2020 at 8:23 AM Florian Weimer via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> The subdirectories match those in the x86-64 psABI:
>
> https://gitlab.com/x86-psABIs/x86-64-ABI/-/commit/77566eb03bc6a326811cb7e9a6b9396884b67c7c
> ---
>  sysdeps/x86_64/Makefile            | 36 +++++++++++++++-
>  sysdeps/x86_64/dl-hwcaps-subdirs.c | 66 ++++++++++++++++++++++++++++++
>  sysdeps/x86_64/tst-glibc-hwcaps.c  | 65 +++++++++++++++++++++++++++++
>  3 files changed, 166 insertions(+), 1 deletion(-)
>  create mode 100644 sysdeps/x86_64/dl-hwcaps-subdirs.c
>  create mode 100644 sysdeps/x86_64/tst-glibc-hwcaps.c
>
> diff --git a/sysdeps/x86_64/Makefile b/sysdeps/x86_64/Makefile
> index 42b97c5cc7..16030715e7 100644
> --- a/sysdeps/x86_64/Makefile
> +++ b/sysdeps/x86_64/Makefile
> @@ -144,7 +144,41 @@ CFLAGS-tst-auditmod10b.c += $(AVX512-CFLAGS)
>  CFLAGS-tst-avx512-aux.c += $(AVX512-CFLAGS)
>  CFLAGS-tst-avx512mod.c += $(AVX512-CFLAGS)
>  endif
> -endif
> +
> +$(objpfx)tst-glibc-hwcaps: \
> +  $(objpfx)markermod2-1.so $(objpfx)markermod3-1.so $(objpfx)markermod4-1.so
> +$(objpfx)tst-glibc-hwcaps.out: \
> +  $(objpfx)markermod2.so \
> +    $(objpfx)glibc-hwcaps/x86-64-v2/markermod2.so \
> +  $(objpfx)markermod3.so \
> +    $(objpfx)glibc-hwcaps/x86-64-v2/markermod3.so \
> +    $(objpfx)glibc-hwcaps/x86-64-v3/markermod3.so \
> +  $(objpfx)markermod4.so \
> +    $(objpfx)glibc-hwcaps/x86-64-v2/markermod4.so \
> +    $(objpfx)glibc-hwcaps/x86-64-v3/markermod4.so \
> +    $(objpfx)glibc-hwcaps/x86-64-v4/markermod4.so \
> +
> +$(objpfx)glibc-hwcaps/x86-64-v2/markermod2.so: $(objpfx)markermod2-2.so
> +       $(make-target-directory)
> +       cp $< $@
> +$(objpfx)glibc-hwcaps/x86-64-v2/markermod3.so: $(objpfx)markermod3-2.so
> +       $(make-target-directory)
> +       cp $< $@
> +$(objpfx)glibc-hwcaps/x86-64-v3/markermod3.so: $(objpfx)markermod3-3.so
> +       $(make-target-directory)
> +       cp $< $@
> +$(objpfx)glibc-hwcaps/x86-64-v2/markermod4.so: $(objpfx)markermod4-2.so
> +       $(make-target-directory)
> +       cp $< $@
> +$(objpfx)glibc-hwcaps/x86-64-v3/markermod4.so: $(objpfx)markermod4-3.so
> +       $(make-target-directory)
> +       cp $< $@
> +$(objpfx)glibc-hwcaps/x86-64-v4/markermod4.so: $(objpfx)markermod4-4.so
> +       $(make-target-directory)
> +       cp $< $@
> +
> +
> +endif # $(subdir) == elf
>
>  ifeq ($(subdir),csu)
>  gen-as-const-headers += tlsdesc.sym rtld-offsets.sym
> diff --git a/sysdeps/x86_64/dl-hwcaps-subdirs.c b/sysdeps/x86_64/dl-hwcaps-subdirs.c
> new file mode 100644
> index 0000000000..c4d8b3a02a
> --- /dev/null
> +++ b/sysdeps/x86_64/dl-hwcaps-subdirs.c
> @@ -0,0 +1,66 @@
> +/* Architecture-specific glibc-hwcaps subdirectories.  x86 version.
> +   Copyright (C) 2020 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <dl-hwcaps.h>
> +#include <cpu-features.h>
>

Please use <sys/platform/x86.h>.

> +const char _dl_hwcaps_subdirs[] = "x86-64-v4:x86-64-v3:x86-64-v2";
> +enum { subdirs_count = 3 };
> +
> +uint32_t
> +_dl_hwcaps_subdirs_active (void)
> +{
> +  int active = 0;
> +
> +  /* Test in reverse preference order.  */
> +
> +  /* x86-64-v2.  */
> +  if (!(CPU_FEATURE_USABLE (CMPXCHG16B)
> +        && CPU_FEATURE_USABLE (LAHF64_SAHF64)
> +        && CPU_FEATURE_USABLE (POPCNT)
> +        && CPU_FEATURE_USABLE (SSE3)
> +        && CPU_FEATURE_USABLE (SSE4_1)
> +        && CPU_FEATURE_USABLE (SSE4_2)
> +        && CPU_FEATURE_USABLE (SSSE3)))
> +    return _dl_hwcaps_subdirs_build_bitmask (subdirs_count, active);
> +  ++active;
> +
> +  /* x86-64-v3.  */
> +  if (!(CPU_FEATURE_USABLE (AVX)
> +        && CPU_FEATURE_USABLE (AVX2)
> +        && CPU_FEATURE_USABLE (BMI1)
> +        && CPU_FEATURE_USABLE (BMI2)
> +        && CPU_FEATURE_USABLE (F16C)
> +        && CPU_FEATURE_USABLE (FMA)
> +        && CPU_FEATURE_USABLE (LZCNT)
> +        && CPU_FEATURE_USABLE (MOVBE)
> +        && CPU_FEATURE_USABLE (OSXSAVE)))
> +    return _dl_hwcaps_subdirs_build_bitmask (subdirs_count, active);
> +  ++active;
> +
> + /* x86-64-v4.  */
> +  if (!(CPU_FEATURE_USABLE (AVX512F)
> +        && CPU_FEATURE_USABLE (AVX512BW)
> +        && CPU_FEATURE_USABLE (AVX512CD)
> +        && CPU_FEATURE_USABLE (AVX512DQ)
> +        && CPU_FEATURE_USABLE (AVX512VL)))
> +    return _dl_hwcaps_subdirs_build_bitmask (subdirs_count, active);
> +  ++active;
> +
> +  return _dl_hwcaps_subdirs_build_bitmask (subdirs_count, active);
> +}
> diff --git a/sysdeps/x86_64/tst-glibc-hwcaps.c b/sysdeps/x86_64/tst-glibc-hwcaps.c
> new file mode 100644
> index 0000000000..b46e7cb236
> --- /dev/null
> +++ b/sysdeps/x86_64/tst-glibc-hwcaps.c
> @@ -0,0 +1,65 @@
> +/* glibc-hwcaps subdirectory test.  x86_64 version.
> +   Copyright (C) 2020 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <stdio.h>
> +#include <support/check.h>
> +#include <sys/param.h>

Please include <sys/platform/x86.h>.

> +extern int marker2 (void);
> +extern int marker3 (void);
> +extern int marker4 (void);
> +
> +/* Return the x86-64-vN level, 1 for the baseline.  */
> +static int
> +compute_level (void)
> +{
> +  /* These checks are not entirely accurate because they are limited
> +     by GCC capabilities.  But wrong results will only result from
> +     inconsistent CPU models involving virtualization.  */

Please use

  const struct cpu_features *cpu_features
    = __x86_get_cpu_features (COMMON_CPUID_INDEX_MAX);

 if (CPU_FEATURE_USABLE_P (cpu_features, CMPXCHG16B)
      && CPU_FEATURE_USABLE_P (cpu_features, LAHF64_SAHF64)
      && CPU_FEATURE_USABLE_P (cpu_features, POPCNT)
      && CPU_FEATURE_USABLE_P (cpu_features, MMX)
      && CPU_FEATURE_USABLE_P (cpu_features, SSE)
      && CPU_FEATURE_USABLE_P (cpu_features, SSE2)
      && CPU_FEATURE_USABLE_P (cpu_features, SSE3)
      && CPU_FEATURE_USABLE_P (cpu_features, SSSE3)
      && CPU_FEATURE_USABLE_P (cpu_features, SSE4_1)
      && CPU_FEATURE_USABLE_P (cpu_features, SSE4_2))
...

> +  if (!(__builtin_cpu_supports ("sse3")
> +        && __builtin_cpu_supports ("sse4.1")
> +        && __builtin_cpu_supports ("sse4.2")
> +        && __builtin_cpu_supports ("ssse3")))
> +    return 1;
> +  if (!(__builtin_cpu_supports ("avx")
> +        && __builtin_cpu_supports ("avx2")
> +        && __builtin_cpu_supports ("bmi")
> +        && __builtin_cpu_supports ("bmi2")
> +        && __builtin_cpu_supports ("fma")))
> +    return 2;
> +  if (!(__builtin_cpu_supports ("avx512f")
> +        && __builtin_cpu_supports ("avx512bw")
> +        && __builtin_cpu_supports ("avx512cd")
> +        && __builtin_cpu_supports ("avx512dq")
> +        && __builtin_cpu_supports ("avx512vl")))
> +    return 3;
> +  return 4;
> +}
> +
> +static int
> +do_test (void)
> +{
> +  int level = compute_level ();
> +  printf ("info: detected x86-64 micro-architecture level: %d\n", level);
> +  TEST_COMPARE (marker2 (), MIN (level, 2));
> +  TEST_COMPARE (marker3 (), MIN (level, 3));
> +  TEST_COMPARE (marker4 (), MIN (level, 4));
> +  return 0;
> +}
> +
> +#include <support/test-driver.c>
> --
> Red Hat GmbH, https://de.redhat.com/ , Registered seat: Grasbrunn,
> Commercial register: Amtsgericht Muenchen, HRB 153243,
> Managing Directors: Charles Cachera, Brian Klemm, Laurie Krebs, Michael O'Neill
>
>
Florian Weimer Oct. 13, 2020, 9:29 a.m. UTC | #2
* H. J. Lu via Libc-alpha:

>> diff --git a/sysdeps/x86_64/dl-hwcaps-subdirs.c b/sysdeps/x86_64/dl-hwcaps-subdirs.c
>> new file mode 100644
>> index 0000000000..c4d8b3a02a
>> --- /dev/null
>> +++ b/sysdeps/x86_64/dl-hwcaps-subdirs.c

>> +#include <dl-hwcaps.h>
>> +#include <cpu-features.h>
>>
>
> Please use <sys/platform/x86.h>.

How does this work?  There is no wrapper header for it, so its
functionality is not really available within ld.so.

>> diff --git a/sysdeps/x86_64/tst-glibc-hwcaps.c b/sysdeps/x86_64/tst-glibc-hwcaps.c
>> new file mode 100644
>> index 0000000000..b46e7cb236
>> --- /dev/null
>> +++ b/sysdeps/x86_64/tst-glibc-hwcaps.c

>> +#include <stdio.h>
>> +#include <support/check.h>
>> +#include <sys/param.h>
>
> Please include <sys/platform/x86.h>.

I don't want to test the implementation against itself.  I'd rather use
the GCC functionality and if necessary, add the additional feature
checks by open-coding the CPU analysis.

Thanks,
Florian
H.J. Lu Oct. 13, 2020, 11:02 a.m. UTC | #3
On Tue, Oct 13, 2020 at 2:29 AM Florian Weimer <fweimer@redhat.com> wrote:
>
> * H. J. Lu via Libc-alpha:
>
> >> diff --git a/sysdeps/x86_64/dl-hwcaps-subdirs.c b/sysdeps/x86_64/dl-hwcaps-subdirs.c
> >> new file mode 100644
> >> index 0000000000..c4d8b3a02a
> >> --- /dev/null
> >> +++ b/sysdeps/x86_64/dl-hwcaps-subdirs.c
>
> >> +#include <dl-hwcaps.h>
> >> +#include <cpu-features.h>
> >>
> >
> > Please use <sys/platform/x86.h>.
>
> How does this work?  There is no wrapper header for it, so its
> functionality is not really available within ld.so.

You are right.

> >> diff --git a/sysdeps/x86_64/tst-glibc-hwcaps.c b/sysdeps/x86_64/tst-glibc-hwcaps.c
> >> new file mode 100644
> >> index 0000000000..b46e7cb236
> >> --- /dev/null
> >> +++ b/sysdeps/x86_64/tst-glibc-hwcaps.c
>
> >> +#include <stdio.h>
> >> +#include <support/check.h>
> >> +#include <sys/param.h>
> >
> > Please include <sys/platform/x86.h>.
>
> I don't want to test the implementation against itself.  I'd rather use
> the GCC functionality and if necessary, add the additional feature
> checks by open-coding the CPU analysis.

You need to check all ISAs included in each ISA level.
There are testcases to check that <sys/platform/x86.h>
is correct.
Florian Weimer Oct. 13, 2020, 11:24 a.m. UTC | #4
* H. J. Lu via Libc-alpha:

> On Tue, Oct 13, 2020 at 2:29 AM Florian Weimer <fweimer@redhat.com> wrote:
>>
>> * H. J. Lu via Libc-alpha:
>>
>> >> diff --git a/sysdeps/x86_64/dl-hwcaps-subdirs.c b/sysdeps/x86_64/dl-hwcaps-subdirs.c
>> >> new file mode 100644
>> >> index 0000000000..c4d8b3a02a
>> >> --- /dev/null
>> >> +++ b/sysdeps/x86_64/dl-hwcaps-subdirs.c
>>
>> >> +#include <dl-hwcaps.h>
>> >> +#include <cpu-features.h>
>> >>
>> >
>> > Please use <sys/platform/x86.h>.
>>
>> How does this work?  There is no wrapper header for it, so its
>> functionality is not really available within ld.so.
>
> You are right.

So this part is okay?

>> >> diff --git a/sysdeps/x86_64/tst-glibc-hwcaps.c b/sysdeps/x86_64/tst-glibc-hwcaps.c
>> >> new file mode 100644
>> >> index 0000000000..b46e7cb236
>> >> --- /dev/null
>> >> +++ b/sysdeps/x86_64/tst-glibc-hwcaps.c
>>
>> >> +#include <stdio.h>
>> >> +#include <support/check.h>
>> >> +#include <sys/param.h>
>> >
>> > Please include <sys/platform/x86.h>.
>>
>> I don't want to test the implementation against itself.  I'd rather use
>> the GCC functionality and if necessary, add the additional feature
>> checks by open-coding the CPU analysis.
>
> You need to check all ISAs included in each ISA level.
> There are testcases to check that <sys/platform/x86.h>
> is correct.

Do you still want me to use <sys/platform/x86.h> then?

Thanks,
Florian
H.J. Lu Oct. 13, 2020, 11:43 a.m. UTC | #5
On Tue, Oct 13, 2020 at 4:25 AM Florian Weimer <fweimer@redhat.com> wrote:
>
> * H. J. Lu via Libc-alpha:
>
> > On Tue, Oct 13, 2020 at 2:29 AM Florian Weimer <fweimer@redhat.com> wrote:
> >>
> >> * H. J. Lu via Libc-alpha:
> >>
> >> >> diff --git a/sysdeps/x86_64/dl-hwcaps-subdirs.c b/sysdeps/x86_64/dl-hwcaps-subdirs.c
> >> >> new file mode 100644
> >> >> index 0000000000..c4d8b3a02a
> >> >> --- /dev/null
> >> >> +++ b/sysdeps/x86_64/dl-hwcaps-subdirs.c
> >>
> >> >> +#include <dl-hwcaps.h>
> >> >> +#include <cpu-features.h>
> >> >>
> >> >
> >> > Please use <sys/platform/x86.h>.
> >>
> >> How does this work?  There is no wrapper header for it, so its
> >> functionality is not really available within ld.so.
> >
> > You are right.
>
> So this part is okay?

Yes.

> >> >> diff --git a/sysdeps/x86_64/tst-glibc-hwcaps.c b/sysdeps/x86_64/tst-glibc-hwcaps.c
> >> >> new file mode 100644
> >> >> index 0000000000..b46e7cb236
> >> >> --- /dev/null
> >> >> +++ b/sysdeps/x86_64/tst-glibc-hwcaps.c
> >>
> >> >> +#include <stdio.h>
> >> >> +#include <support/check.h>
> >> >> +#include <sys/param.h>
> >> >
> >> > Please include <sys/platform/x86.h>.
> >>
> >> I don't want to test the implementation against itself.  I'd rather use
> >> the GCC functionality and if necessary, add the additional feature
> >> checks by open-coding the CPU analysis.
> >
> > You need to check all ISAs included in each ISA level.
> > There are testcases to check that <sys/platform/x86.h>
> > is correct.
>
> Do you still want me to use <sys/platform/x86.h> then?
>

Yes.
diff mbox series

Patch

diff --git a/sysdeps/x86_64/Makefile b/sysdeps/x86_64/Makefile
index 42b97c5cc7..16030715e7 100644
--- a/sysdeps/x86_64/Makefile
+++ b/sysdeps/x86_64/Makefile
@@ -144,7 +144,41 @@  CFLAGS-tst-auditmod10b.c += $(AVX512-CFLAGS)
 CFLAGS-tst-avx512-aux.c += $(AVX512-CFLAGS)
 CFLAGS-tst-avx512mod.c += $(AVX512-CFLAGS)
 endif
-endif
+
+$(objpfx)tst-glibc-hwcaps: \
+  $(objpfx)markermod2-1.so $(objpfx)markermod3-1.so $(objpfx)markermod4-1.so
+$(objpfx)tst-glibc-hwcaps.out: \
+  $(objpfx)markermod2.so \
+    $(objpfx)glibc-hwcaps/x86-64-v2/markermod2.so \
+  $(objpfx)markermod3.so \
+    $(objpfx)glibc-hwcaps/x86-64-v2/markermod3.so \
+    $(objpfx)glibc-hwcaps/x86-64-v3/markermod3.so \
+  $(objpfx)markermod4.so \
+    $(objpfx)glibc-hwcaps/x86-64-v2/markermod4.so \
+    $(objpfx)glibc-hwcaps/x86-64-v3/markermod4.so \
+    $(objpfx)glibc-hwcaps/x86-64-v4/markermod4.so \
+
+$(objpfx)glibc-hwcaps/x86-64-v2/markermod2.so: $(objpfx)markermod2-2.so
+	$(make-target-directory)
+	cp $< $@
+$(objpfx)glibc-hwcaps/x86-64-v2/markermod3.so: $(objpfx)markermod3-2.so
+	$(make-target-directory)
+	cp $< $@
+$(objpfx)glibc-hwcaps/x86-64-v3/markermod3.so: $(objpfx)markermod3-3.so
+	$(make-target-directory)
+	cp $< $@
+$(objpfx)glibc-hwcaps/x86-64-v2/markermod4.so: $(objpfx)markermod4-2.so
+	$(make-target-directory)
+	cp $< $@
+$(objpfx)glibc-hwcaps/x86-64-v3/markermod4.so: $(objpfx)markermod4-3.so
+	$(make-target-directory)
+	cp $< $@
+$(objpfx)glibc-hwcaps/x86-64-v4/markermod4.so: $(objpfx)markermod4-4.so
+	$(make-target-directory)
+	cp $< $@
+
+
+endif # $(subdir) == elf
 
 ifeq ($(subdir),csu)
 gen-as-const-headers += tlsdesc.sym rtld-offsets.sym
diff --git a/sysdeps/x86_64/dl-hwcaps-subdirs.c b/sysdeps/x86_64/dl-hwcaps-subdirs.c
new file mode 100644
index 0000000000..c4d8b3a02a
--- /dev/null
+++ b/sysdeps/x86_64/dl-hwcaps-subdirs.c
@@ -0,0 +1,66 @@ 
+/* Architecture-specific glibc-hwcaps subdirectories.  x86 version.
+   Copyright (C) 2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <dl-hwcaps.h>
+#include <cpu-features.h>
+
+const char _dl_hwcaps_subdirs[] = "x86-64-v4:x86-64-v3:x86-64-v2";
+enum { subdirs_count = 3 };
+
+uint32_t
+_dl_hwcaps_subdirs_active (void)
+{
+  int active = 0;
+
+  /* Test in reverse preference order.  */
+
+  /* x86-64-v2.  */
+  if (!(CPU_FEATURE_USABLE (CMPXCHG16B)
+        && CPU_FEATURE_USABLE (LAHF64_SAHF64)
+        && CPU_FEATURE_USABLE (POPCNT)
+        && CPU_FEATURE_USABLE (SSE3)
+        && CPU_FEATURE_USABLE (SSE4_1)
+        && CPU_FEATURE_USABLE (SSE4_2)
+        && CPU_FEATURE_USABLE (SSSE3)))
+    return _dl_hwcaps_subdirs_build_bitmask (subdirs_count, active);
+  ++active;
+
+  /* x86-64-v3.  */
+  if (!(CPU_FEATURE_USABLE (AVX)
+        && CPU_FEATURE_USABLE (AVX2)
+        && CPU_FEATURE_USABLE (BMI1)
+        && CPU_FEATURE_USABLE (BMI2)
+        && CPU_FEATURE_USABLE (F16C)
+        && CPU_FEATURE_USABLE (FMA)
+        && CPU_FEATURE_USABLE (LZCNT)
+        && CPU_FEATURE_USABLE (MOVBE)
+        && CPU_FEATURE_USABLE (OSXSAVE)))
+    return _dl_hwcaps_subdirs_build_bitmask (subdirs_count, active);
+  ++active;
+
+ /* x86-64-v4.  */
+  if (!(CPU_FEATURE_USABLE (AVX512F)
+        && CPU_FEATURE_USABLE (AVX512BW)
+        && CPU_FEATURE_USABLE (AVX512CD)
+        && CPU_FEATURE_USABLE (AVX512DQ)
+        && CPU_FEATURE_USABLE (AVX512VL)))
+    return _dl_hwcaps_subdirs_build_bitmask (subdirs_count, active);
+  ++active;
+
+  return _dl_hwcaps_subdirs_build_bitmask (subdirs_count, active);
+}
diff --git a/sysdeps/x86_64/tst-glibc-hwcaps.c b/sysdeps/x86_64/tst-glibc-hwcaps.c
new file mode 100644
index 0000000000..b46e7cb236
--- /dev/null
+++ b/sysdeps/x86_64/tst-glibc-hwcaps.c
@@ -0,0 +1,65 @@ 
+/* glibc-hwcaps subdirectory test.  x86_64 version.
+   Copyright (C) 2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <stdio.h>
+#include <support/check.h>
+#include <sys/param.h>
+
+extern int marker2 (void);
+extern int marker3 (void);
+extern int marker4 (void);
+
+/* Return the x86-64-vN level, 1 for the baseline.  */
+static int
+compute_level (void)
+{
+  /* These checks are not entirely accurate because they are limited
+     by GCC capabilities.  But wrong results will only result from
+     inconsistent CPU models involving virtualization.  */
+  if (!(__builtin_cpu_supports ("sse3")
+        && __builtin_cpu_supports ("sse4.1")
+        && __builtin_cpu_supports ("sse4.2")
+        && __builtin_cpu_supports ("ssse3")))
+    return 1;
+  if (!(__builtin_cpu_supports ("avx")
+        && __builtin_cpu_supports ("avx2")
+        && __builtin_cpu_supports ("bmi")
+        && __builtin_cpu_supports ("bmi2")
+        && __builtin_cpu_supports ("fma")))
+    return 2;
+  if (!(__builtin_cpu_supports ("avx512f")
+        && __builtin_cpu_supports ("avx512bw")
+        && __builtin_cpu_supports ("avx512cd")
+        && __builtin_cpu_supports ("avx512dq")
+        && __builtin_cpu_supports ("avx512vl")))
+    return 3;
+  return 4;
+}
+
+static int
+do_test (void)
+{
+  int level = compute_level ();
+  printf ("info: detected x86-64 micro-architecture level: %d\n", level);
+  TEST_COMPARE (marker2 (), MIN (level, 2));
+  TEST_COMPARE (marker3 (), MIN (level, 3));
+  TEST_COMPARE (marker4 (), MIN (level, 4));
+  return 0;
+}
+
+#include <support/test-driver.c>