buildtools/gcc/libgcc/config/aarch64/lse-init.c

/* Out-of-line LSE atomics for AArch64 architecture, Init.
   Copyright (C) 2019-2024 Free Software Foundation, Inc.
   Contributed by Linaro Ltd.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.

GCC 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 General Public License
for more details.

Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
<http://www.gnu.org/licenses/>.  */

#include "auto-target.h"

/* Define the symbol gating the LSE implementations.  */
_Bool __aarch64_have_lse_atomics
  __attribute__((visibility("hidden"), nocommon));

/* Gate availability of __getauxval on glibc.  All AArch64-supporting glibc
   versions support it.  */
#ifdef __gnu_linux__

# define AT_HWCAP	16
# define HWCAP_ATOMICS	(1 << 8)

unsigned long int __getauxval (unsigned long int);

/* Use a higher priority to ensure it runs before user constructors
   and library constructors with priority 100. */
static void __attribute__((constructor (90)))
init_have_lse_atomics (void)
{
  unsigned long hwcap = __getauxval (AT_HWCAP);
  __aarch64_have_lse_atomics = (hwcap & HWCAP_ATOMICS) != 0;
}

#endif /* __gnu_linux__  */