LoongArch: Add glibc.cpu.hwcap support.

  The current IFUNC selection is always using the most recent
features which are available via AT_HWCAP.  But in
some scenarios it is useful to adjust this selection.

The environment variable:

GLIBC_TUNABLES=glibc.cpu.hwcaps=-xxx,yyy,zzz,....

can be used to enable HWCAP feature yyy, disable HWCAP feature xxx,
where the feature name is case-sensitive and has to match the ones
used in sysdeps/loongarch/cpu-tunables.c.
---
 manual/tunables.texi                          |   5 +-
 sysdeps/loongarch/Makefile                    |  12 ++
 sysdeps/loongarch/cpu-tunables.c              |  87 +++++++++++
 sysdeps/loongarch/dl-get-cpu-features.c       |  25 ++++
 sysdeps/loongarch/dl-machine.h                |  29 +++-
 sysdeps/loongarch/dl-tunables.list            |  25 ++++
 .../lp64/multiarch/dl-symbol-redir-ifunc.h    |   3 +
 sysdeps/loongarch/tst-hwcap-tunables.c        | 136 ++++++++++++++++++
 .../unix/sysv/linux/loongarch/cpu-features.c  |  30 ++++
 .../unix/sysv/linux/loongarch/cpu-features.h  |  17 ++-
 .../unix/sysv/linux/loongarch/dl-procinfo.c   |  60 ++++++++
 sysdeps/unix/sysv/linux/loongarch/dl-sysdep.c |  21 +++
 .../unix/sysv/linux/loongarch/libc-start.c    |  34 +++++
 13 files changed, 475 insertions(+), 9 deletions(-)
 create mode 100644 sysdeps/loongarch/cpu-tunables.c
 create mode 100644 sysdeps/loongarch/dl-get-cpu-features.c
 create mode 100644 sysdeps/loongarch/dl-tunables.list
 create mode 100644 sysdeps/loongarch/tst-hwcap-tunables.c
 create mode 100644 sysdeps/unix/sysv/linux/loongarch/cpu-features.c
 create mode 100644 sysdeps/unix/sysv/linux/loongarch/dl-procinfo.c
 create mode 100644 sysdeps/unix/sysv/linux/loongarch/dl-sysdep.c
 create mode 100644 sysdeps/unix/sysv/linux/loongarch/libc-start.c
  

On 23/04/24 09:48, caiyinyu wrote:
> The current IFUNC selection is always using the most recent
> features which are available via AT_HWCAP.  But in
> some scenarios it is useful to adjust this selection.
> 
> The environment variable:
> 
> GLIBC_TUNABLES=glibc.cpu.hwcaps=-xxx,yyy,zzz,....
> 
> can be used to enable HWCAP feature yyy, disable HWCAP feature xxx,
> where the feature name is case-sensitive and has to match the ones
> used in sysdeps/loongarch/cpu-tunables.c.

The patch looks good, just two minor style issues below.

> ---
>  manual/tunables.texi                          |   5 +-
>  sysdeps/loongarch/Makefile                    |  12 ++
>  sysdeps/loongarch/cpu-tunables.c              |  87 +++++++++++
>  sysdeps/loongarch/dl-get-cpu-features.c       |  25 ++++
>  sysdeps/loongarch/dl-machine.h                |  29 +++-
>  sysdeps/loongarch/dl-tunables.list            |  25 ++++
>  .../lp64/multiarch/dl-symbol-redir-ifunc.h    |   3 +
>  sysdeps/loongarch/tst-hwcap-tunables.c        | 136 ++++++++++++++++++
>  .../unix/sysv/linux/loongarch/cpu-features.c  |  30 ++++
>  .../unix/sysv/linux/loongarch/cpu-features.h  |  17 ++-
>  .../unix/sysv/linux/loongarch/dl-procinfo.c   |  60 ++++++++
>  sysdeps/unix/sysv/linux/loongarch/dl-sysdep.c |  21 +++
>  .../unix/sysv/linux/loongarch/libc-start.c    |  34 +++++
>  13 files changed, 475 insertions(+), 9 deletions(-)
>  create mode 100644 sysdeps/loongarch/cpu-tunables.c
>  create mode 100644 sysdeps/loongarch/dl-get-cpu-features.c
>  create mode 100644 sysdeps/loongarch/dl-tunables.list
>  create mode 100644 sysdeps/loongarch/tst-hwcap-tunables.c
>  create mode 100644 sysdeps/unix/sysv/linux/loongarch/cpu-features.c
>  create mode 100644 sysdeps/unix/sysv/linux/loongarch/dl-procinfo.c
>  create mode 100644 sysdeps/unix/sysv/linux/loongarch/dl-sysdep.c
>  create mode 100644 sysdeps/unix/sysv/linux/loongarch/libc-start.c
> 
> diff --git a/manual/tunables.texi b/manual/tunables.texi
> index 4a7d04dc0d..baaf751721 100644
> --- a/manual/tunables.texi
> +++ b/manual/tunables.texi
> @@ -525,7 +525,10 @@ a CPU arch-level like @code{z13} instead of single HWCAP and STFLE features.
>  On powerpc, the supported HWCAP and HWCAP2 features can be found in
>  @code{sysdeps/powerpc/dl-procinfo.c}.
>  
> -This tunable is specific to i386, x86-64, s390x and powerpc.
> +On loongarch, the supported HWCAP features can be found in
> +@code{sysdeps/loongarch/cpu-tunables.c}.
> +
> +This tunable is specific to i386, x86-64, s390x, powerpc and loongarch.
>  @end deftp
>  
>  @deftp Tunable glibc.cpu.cached_memopt

Ok.  As a side note, from a recent BZ report [1] I think maybe we should
start to proper document the supported HWCAP for ifunc selection instead
of reference a source file.

[1] https://sourceware.org/bugzilla/show_bug.cgi?id=31675

> diff --git a/sysdeps/loongarch/Makefile b/sysdeps/loongarch/Makefile
> index 43d2f583cd..965daae571 100644
> --- a/sysdeps/loongarch/Makefile
> +++ b/sysdeps/loongarch/Makefile
> @@ -1,11 +1,23 @@
>  ifeq ($(subdir),misc)
>  sysdep_headers += sys/asm.h
> +
> +tests += \
> +	tst-hwcap-tunables \
> +	# tests
> +
> +tst-hwcap-tunables-ARGS = -- $(host-test-program-cmd)
>  endif
>  
>  ifeq ($(subdir),elf)
>  gen-as-const-headers += dl-link.sym
>  endif
>  
> +ifeq ($(subdir),elf)
> +sysdep-dl-routines += \
> +	dl-get-cpu-features \
> +	# sysdep-dl-routines
> +endif
> +
>  # LoongArch's assembler also needs to know about PIC as it changes the
>  # definition of some assembler macros.
>  ASFLAGS-.os += $(pic-ccflag)

Minor nit, other files use a double space instead of tab for each new entry.

> diff --git a/sysdeps/loongarch/cpu-tunables.c b/sysdeps/loongarch/cpu-tunables.c
> new file mode 100644
> index 0000000000..e274e993c1
> --- /dev/null
> +++ b/sysdeps/loongarch/cpu-tunables.c
> @@ -0,0 +1,87 @@
> +/* LoongArch CPU feature tuning.
> +   This file is part of the GNU C Library.
> +   Copyright (C) 2024 Free Software Foundation, Inc.
> +
> +   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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include <stdbool.h>
> +#include <stdint.h>
> +#include <unistd.h>		/* Get STDOUT_FILENO for _dl_printf.  */
> +#include <elf/dl-tunables.h>
> +#include <string.h>
> +#include <cpu-features.h>
> +#include <ldsodefs.h>
> +#include <sys/auxv.h>
> +#include <dl-tunables-parse.h>
> +#include <dl-symbol-redir-ifunc.h>
> +
> +#define CHECK_GLIBC_IFUNC_CPU(f, name, len)			\
> +  _Static_assert (sizeof (#name) - 1 == len, #name " != " #len);	\
> +  if (tunable_str_comma_strcmp_cte (&f, #name))				\
> +    {									\
> +      if (f.disable)							\
> +	GLRO(dl_larch_cpu_features).hwcap &= (~HWCAP_LOONGARCH_##name);	\
> +      else								\
> +	GLRO(dl_larch_cpu_features).hwcap |= HWCAP_LOONGARCH_##name;	\
> +      break;								\
> +    }
> +
> +attribute_hidden void
> +TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)
> +{
> +  /* The current IFUNC selection is based on microbenchmarks in glibc.
> +     It should give the best performance for most workloads.  But other
> +     choices may have better performance for a particular workload or on
> +     the hardware which wasn't available when the selection was made.
> +     The environment variable:
> +
> +     GLIBC_TUNABLES=glibc.cpu.hwcaps=-xxx,yyy,-zzz,....
> +
> +     can be used to enable CPU/ARCH feature yyy, disable CPU/ARCH feature
> +     yyy and zzz, where the feature name is case-sensitive and has to
> +     match the ones in cpu-features.h.  It can be used by glibc developers
> +     to tune for a new processor or override the IFUNC selection to
> +     improve performance for a particular workload.
> +
> +     NOTE: the IFUNC selection may change over time.  Please check all
> +     multiarch implementations when experimenting.  */
> +
> +  struct tunable_str_comma_state_t ts;
> +  tunable_str_comma_init (&ts, valp);
> +
> +  struct tunable_str_comma_t n;
> +  while (tunable_str_comma_next (&ts, &n))
> +    {
> +      switch (n.len)
> +	{
> +	default:
> +	  break;
> +	case 3:
> +	  {
> +	    CHECK_GLIBC_IFUNC_CPU (n, LSX, 3);
> +	    CHECK_GLIBC_IFUNC_CPU (n, UAL, 3);
> +	  }
> +	  break;
> +	case 4:
> +	  {
> +	    CHECK_GLIBC_IFUNC_CPU (n, LASX, 4);
> +	  }
> +	  break;
> +	}
> +    }
> +
> +  /* Ensure that the user has not enabled any unsupported features.  */
> +  GLRO(dl_larch_cpu_features).hwcap &= GLRO(dl_hwcap);
> +}

Ok.

> diff --git a/sysdeps/loongarch/dl-get-cpu-features.c b/sysdeps/loongarch/dl-get-cpu-features.c
> new file mode 100644
> index 0000000000..3dcecefbcd
> --- /dev/null
> +++ b/sysdeps/loongarch/dl-get-cpu-features.c
> @@ -0,0 +1,25 @@
> +/* Define _dl_larch_get_cpu_features.
> +   Copyright (C) 2024 Free Software Foundation, Inc.
> +
> +   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 <ldsodefs.h>
> +
> +const struct cpu_features *
> +_dl_larch_get_cpu_features (void)
> +{
> +  return &GLRO(dl_larch_cpu_features);
> +}

Ok.

> diff --git a/sysdeps/loongarch/dl-machine.h b/sysdeps/loongarch/dl-machine.h
> index ab81b82d95..6baf0e600a 100644
> --- a/sysdeps/loongarch/dl-machine.h
> +++ b/sysdeps/loongarch/dl-machine.h
> @@ -29,6 +29,8 @@
>  #include <dl-static-tls.h>
>  #include <dl-machine-rel.h>
>  
> +#include <cpu-features.c>
> +
>  #ifndef _RTLD_PROLOGUE
>  # define _RTLD_PROLOGUE(entry)					\
>  	".globl\t" __STRING (entry) "\n\t"			\
> @@ -53,6 +55,23 @@
>  #define ELF_MACHINE_NO_REL 1
>  #define ELF_MACHINE_NO_RELA 0
>  
> +#define DL_PLATFORM_INIT dl_platform_init ()
> +
> +static inline void __attribute__ ((unused))
> +dl_platform_init (void)
> +{
> +  if (GLRO(dl_platform) != NULL && *GLRO(dl_platform) == '\0')
> +    /* Avoid an empty string which would disturb us.  */
> +    GLRO(dl_platform) = NULL;
> +
> +#ifdef SHARED
> +  /* init_cpu_features has been called early from __libc_start_main in
> +     static executable.  */
> +  init_cpu_features (&GLRO(dl_larch_cpu_features));
> +#endif
> +}
> +
> +
>  /* Return nonzero iff ELF header is compatible with the running host.  */
>  static inline int
>  elf_machine_matches_host (const ElfW (Ehdr) *ehdr)
> @@ -290,10 +309,10 @@ elf_machine_runtime_setup (struct link_map *l, struct r_scope_elem *scope[],
>  #ifdef SHARED
>        if (profile != 0)
>  	{
> -# if !defined __loongarch_soft_float
> -	  if (SUPPORT_LASX)
> +#if !defined __loongarch_soft_float
> +	  if (RTLD_SUPPORT_LASX)
>  	    gotplt[0] = (ElfW(Addr)) &_dl_runtime_profile_lasx;
> -	  else if (SUPPORT_LSX)
> +	  else if (RTLD_SUPPORT_LSX)
>  	    gotplt[0] = (ElfW(Addr)) &_dl_runtime_profile_lsx;
>  	  else
>  # endif
> @@ -312,9 +331,9 @@ elf_machine_runtime_setup (struct link_map *l, struct r_scope_elem *scope[],
>  	     indicated by the offset on the stack, and then jump to
>  	     the resolved address.  */
>  #if !defined __loongarch_soft_float
> -	  if (SUPPORT_LASX)
> +	  if (RTLD_SUPPORT_LASX)
>  	    gotplt[0] = (ElfW(Addr)) &_dl_runtime_resolve_lasx;
> -	  else if (SUPPORT_LSX)
> +	  else if (RTLD_SUPPORT_LSX)
>  	    gotplt[0] = (ElfW(Addr)) &_dl_runtime_resolve_lsx;
>  	  else
>  #endif

Ok, lazy resolvers should not depend of the glibc.cpu.hwcap value.

> diff --git a/sysdeps/loongarch/dl-tunables.list b/sysdeps/loongarch/dl-tunables.list
> new file mode 100644
> index 0000000000..00869a9fad
> --- /dev/null
> +++ b/sysdeps/loongarch/dl-tunables.list
> @@ -0,0 +1,25 @@
> +# LoongArch specific tunables.
> +# Copyright (C) 2024 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
> +# <http://www.gnu.org/licenses/>.
> +
> +glibc {
> +  cpu {
> +    hwcaps {
> +      type: STRING
> +    }
> +  }
> +}

Ok.

> diff --git a/sysdeps/loongarch/lp64/multiarch/dl-symbol-redir-ifunc.h b/sysdeps/loongarch/lp64/multiarch/dl-symbol-redir-ifunc.h
> index cb640d77b7..a73390b12f 100644
> --- a/sysdeps/loongarch/lp64/multiarch/dl-symbol-redir-ifunc.h
> +++ b/sysdeps/loongarch/lp64/multiarch/dl-symbol-redir-ifunc.h
> @@ -19,6 +19,9 @@
>  #ifndef _DL_IFUNC_GENERIC_H
>  #define _DL_IFUNC_GENERIC_H
>  
> +#ifndef SHARED
>  asm ("memset = __memset_aligned");
> +asm ("memcmp = __memcmp_aligned");
> +#endif
>  
>  #endif

Ok.

> diff --git a/sysdeps/loongarch/tst-hwcap-tunables.c b/sysdeps/loongarch/tst-hwcap-tunables.c
> new file mode 100644
> index 0000000000..e6856ad042
> --- /dev/null
> +++ b/sysdeps/loongarch/tst-hwcap-tunables.c
> @@ -0,0 +1,136 @@
> +/* Tests for powerpc GLIBC_TUNABLES=glibc.cpu.hwcaps filter.
> +   Copyright (C) 2024 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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include <array_length.h>
> +#include <getopt.h>
> +#include <ifunc-impl-list.h>
> +#include <spawn.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <support/check.h>
> +#include <support/support.h>
> +#include <support/xunistd.h>
> +#include <sys/auxv.h>
> +#include <sys/wait.h>
> +
> +/* Nonzero if the program gets called via `exec'.  */
> +#define CMDLINE_OPTIONS \
> +  { "restart", no_argument, &restart, 1 }, \
> +  { "enable", no_argument, &enable, 1 },
> +static int restart;
> +static int enable;
> +
> +/* Hold the four initial argument used to respawn the process, plus the extra
> +   '--direct', '--restart', and the function to check.  */
> +static char *spargs[9];
> +static int fc;
> +
> +/* Called on process re-execution.  */
> +_Noreturn static void
> +handle_restart (int argc, char *argv[])
> +{
> +  TEST_VERIFY_EXIT (argc == 1);
> +  const char *funcname = argv[0];
> +
> +  struct libc_ifunc_impl impls[32];
> +  int cnt = __libc_ifunc_impl_list ("memcpy", impls, array_length (impls));
> +  if (cnt == 0)
> +    _exit (EXIT_SUCCESS);
> +  TEST_VERIFY_EXIT (cnt >= 1);
> +  for (int i = 0; i < cnt; i++)
> +  {
> +    if (strcmp (impls[i].name, funcname) == 0)
> +      {
> +	if (enable && impls[i].usable != true)
> +	  FAIL_EXIT1 ("FAIL: %s ifunc selection is not enabled.\n", funcname);
> +	else if (!enable && impls[i].usable != false)
> +	  FAIL_EXIT1 ("FAIL: %s ifunc selection is not disabled.\n", funcname);
> +	break;
> +      }
> +  }
> +
> +  _exit (EXIT_SUCCESS);
> +}
> +
> +static void
> +run_test (const char *filter, const char *funcname, int disable)
> +{
> +  if (disable)
> +    printf ("info: checking filter %s (expect %s ifunc "
> +	    "selection to be disabled)\n", filter, funcname);
> +  else
> +    {
> +      printf ("info: checking filter %s (expect %s ifunc "
> +	      "selection to be enabled)\n", filter, funcname);
> +      spargs[fc++] = (char *) "--enable";
> +    }
> +
> +  char *tunable = xasprintf ("GLIBC_TUNABLES=glibc.cpu.hwcaps=%s", filter);
> +  char *const newenvs[] = { (char*) tunable, NULL };
> +  spargs[fc] = (char *) funcname;
> +
> +  pid_t pid;
> +  TEST_COMPARE (posix_spawn (&pid, spargs[0], NULL, NULL, spargs, newenvs), 0);
> +  int status;
> +  TEST_COMPARE (xwaitpid (pid, &status, 0), pid);
> +  TEST_VERIFY (WIFEXITED (status));
> +  TEST_VERIFY (!WIFSIGNALED (status));
> +  TEST_COMPARE (WEXITSTATUS (status), 0);
> +
> +  if (!disable)
> +    fc--;
> +  free (tunable);
> +}
> +
> +static int
> +do_test (int argc, char *argv[])
> +{
> +  if (restart)
> +    handle_restart (argc - 1, &argv[1]);
> +
> +  TEST_VERIFY_EXIT (argc == 2 || argc == 5);
> +
> +  int i;
> +  for (i = 0; i < argc - 1; i++)
> +    spargs[i] = argv[i + 1];
> +  spargs[i++] = (char *) "--direct";
> +  spargs[i++] = (char *) "--restart";
> +  fc = i++;
> +  spargs[i] = NULL;
> +
> +  unsigned long int hwcap = getauxval (AT_HWCAP);
> +
> +  if (hwcap & HWCAP_LOONGARCH_LASX)
> +    run_test ("-LASX", "__memcpy_lasx", 1);
> +  if (hwcap & HWCAP_LOONGARCH_LSX)
> +    run_test ("-LSX", "__memcpy_lsx", 1);
> +  if (hwcap & HWCAP_LOONGARCH_UAL)
> +    run_test ("-UAL", "__memcpy_unaligned", 1);
> +
> +  /* __memcpy_aligned is the default ifunc selection and will be
> +   * always enabled.  */
> +  run_test ("-LASX,-LSX,-UAL", "__memcpy_aligned", 0);
> +  run_test ("-LASX,-LSX", "__memcpy_aligned", 0);
> +  run_test ("-LASX", "__memcpy_aligned", 0);
> +
> +  return 0;
> +}
> +
> +#define TEST_FUNCTION_ARGV do_test
> +#include <support/test-driver.c>

Ok.

> diff --git a/sysdeps/unix/sysv/linux/loongarch/cpu-features.c b/sysdeps/unix/sysv/linux/loongarch/cpu-features.c
> new file mode 100644
> index 0000000000..9c526516d8
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/loongarch/cpu-features.c
> @@ -0,0 +1,30 @@
> +/* Initialize CPU feature data.  LoongArch64 version.
> +   This file is part of the GNU C Library.
> +   Copyright (C) 2024 Free Software Foundation, Inc.
> +
> +   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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include <cpu-features.h>
> +#include <elf/dl-hwcaps.h>
> +#include <elf/dl-tunables.h>
> +extern void TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *) attribute_hidden;
> +
> +static inline void
> +init_cpu_features (struct cpu_features *cpu_features)
> +{
> +    GLRO(dl_larch_cpu_features).hwcap = GLRO(dl_hwcap);
> +    TUNABLE_GET (glibc, cpu, hwcaps, tunable_val_t *,
> +				     TUNABLE_CALLBACK (set_hwcaps));
> +}

Minor nit, the indentation should use double space.

> diff --git a/sysdeps/unix/sysv/linux/loongarch/cpu-features.h b/sysdeps/unix/sysv/linux/loongarch/cpu-features.h
> index 4e863c7469..eec51956a9 100644
> --- a/sysdeps/unix/sysv/linux/loongarch/cpu-features.h
> +++ b/sysdeps/unix/sysv/linux/loongarch/cpu-features.h
> @@ -19,12 +19,23 @@
>  #ifndef _CPU_FEATURES_LOONGARCH64_H
>  #define _CPU_FEATURES_LOONGARCH64_H
>  
> +#include <stdint.h>
>  #include <sys/auxv.h>
>  
> -#define SUPPORT_UAL (GLRO (dl_hwcap) & HWCAP_LOONGARCH_UAL)
> -#define SUPPORT_LSX (GLRO (dl_hwcap) & HWCAP_LOONGARCH_LSX)
> -#define SUPPORT_LASX (GLRO (dl_hwcap) & HWCAP_LOONGARCH_LASX)
> +struct cpu_features
> +{
> +  uint64_t hwcap;
> +};
>  
> +/* Get a pointer to the CPU features structure.  */
> +extern const struct cpu_features *
> +_dl_larch_get_cpu_features (void) __attribute__ ((pure));
> +
> +#define SUPPORT_UAL (GLRO (dl_larch_cpu_features).hwcap & HWCAP_LOONGARCH_UAL)
> +#define SUPPORT_LSX (GLRO (dl_larch_cpu_features).hwcap & HWCAP_LOONGARCH_LSX)
> +#define SUPPORT_LASX (GLRO (dl_larch_cpu_features).hwcap & HWCAP_LOONGARCH_LASX)
> +#define RTLD_SUPPORT_LSX (GLRO (dl_hwcap) & HWCAP_LOONGARCH_LSX)
> +#define RTLD_SUPPORT_LASX (GLRO (dl_hwcap) & HWCAP_LOONGARCH_LASX)
>  #define INIT_ARCH()
>  
>  #endif /* _CPU_FEATURES_LOONGARCH64_H  */

Ok.

> diff --git a/sysdeps/unix/sysv/linux/loongarch/dl-procinfo.c b/sysdeps/unix/sysv/linux/loongarch/dl-procinfo.c
> new file mode 100644
> index 0000000000..5e056a1923
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/loongarch/dl-procinfo.c
> @@ -0,0 +1,60 @@
> +/* Data for LoongArch64 version of processor capability information.
> +   Linux version.
> +   Copyright (C) 2024 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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +/* If anything should be added here check whether the size of each string
> +   is still ok with the given array size.
> +
> +   All the #ifdefs in the definitions are quite irritating but
> +   necessary if we want to avoid duplicating the information.  There
> +   are three different modes:
> +
> +   - PROCINFO_DECL is defined.  This means we are only interested in
> +     declarations.
> +
> +   - PROCINFO_DECL is not defined:
> +
> +     + if SHARED is defined the file is included in an array
> +       initializer.  The .element = { ... } syntax is needed.
> +
> +     + if SHARED is not defined a normal array initialization is
> +       needed.
> +  */
> +
> +#ifndef PROCINFO_CLASS
> +# define PROCINFO_CLASS
> +#endif
> +
> +#if !IS_IN (ldconfig)
> +# if !defined PROCINFO_DECL && defined SHARED
> +  ._dl_larch_cpu_features
> +# else
> +PROCINFO_CLASS struct cpu_features _dl_larch_cpu_features
> +# endif
> +# ifndef PROCINFO_DECL
> += { }
> +# endif
> +# if !defined SHARED || defined PROCINFO_DECL
> +;
> +# else
> +,
> +# endif
> +#endif
> +
> +#undef PROCINFO_DECL
> +#undef PROCINFO_CLASS

Ok.

> diff --git a/sysdeps/unix/sysv/linux/loongarch/dl-sysdep.c b/sysdeps/unix/sysv/linux/loongarch/dl-sysdep.c
> new file mode 100644
> index 0000000000..30b84f1911
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/loongarch/dl-sysdep.c
> @@ -0,0 +1,21 @@
> +/* Operating system support for run-time dynamic linker.  LoongArch version.
> +   Copyright (C) 2024 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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include <config.h>
> +#include <sysdeps/loongarch/cpu-tunables.c>
> +#include <sysdeps/unix/sysv/linux/dl-sysdep.c>

Ok.

> diff --git a/sysdeps/unix/sysv/linux/loongarch/libc-start.c b/sysdeps/unix/sysv/linux/loongarch/libc-start.c
> new file mode 100644
> index 0000000000..e545f7f1d7
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/loongarch/libc-start.c
> @@ -0,0 +1,34 @@
> +/* Override csu/libc-start.c on LoongArch64.
> +   Copyright (C) 2024 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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#ifndef SHARED
> +
> +/* Mark symbols hidden in static PIE for early self relocation to work.  */
> +#if BUILD_PIE_DEFAULT
> +# pragma GCC visibility push (hidden)
> +#endif
> +
> +#include <ldsodefs.h>
> +#include <cpu-features.c>
> +
> +extern struct cpu_features _dl_larch_cpu_features;
> +
> +#define ARCH_INIT_CPU_FEATURES() init_cpu_features (&_dl_larch_cpu_features)
> +
> +#endif
> +#include <csu/libc-start.c>


OK.