glibc/sysdeps/x86/atomic-machine.h

/* Atomic operations.  X86 version.
   Copyright (C) 2018-2025 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/>.  */

#ifndef _X86_ATOMIC_MACHINE_H
#define _X86_ATOMIC_MACHINE_H 1

#ifdef __x86_64__
# define __HAVE_64B_ATOMICS		1
#else
/* Since the Pentium, i386 CPUs have supported 64-bit atomics, but the
   i386 psABI supplement provides only 4-byte alignment for uint64_t
   inside structs, so it is currently not possible to use 64-bit
   atomics on this platform.  */
# define __HAVE_64B_ATOMICS		0
#endif

#define ATOMIC_EXCHANGE_USES_CAS	0

#define atomic_read_barrier() __asm ("" ::: "memory")
#define atomic_write_barrier() __asm ("" ::: "memory")

#define atomic_spin_nop() __asm ("pause")

#endif /* atomic-machine.h */