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glibc/include/atomic.h
Siddhesh Poyarekar 30891f35fa Remove "Contributed by" lines 
We stopped adding "Contributed by" or similar lines in sources in 2012
in favour of git logs and keeping the Contributors section of the
glibc manual up to date.  Removing these lines makes the license
header a bit more consistent across files and also removes the
possibility of error in attribution when license blocks or files are
copied across since the contributed-by lines don't actually reflect
reality in those cases.

Move all "Contributed by" and similar lines (Written by, Test by,
etc.) into a new file CONTRIBUTED-BY to retain record of these
contributions.  These contributors are also mentioned in
manual/contrib.texi, so we just maintain this additional record as a
courtesy to the earlier developers.

The following scripts were used to filter a list of files to edit in
place and to clean up the CONTRIBUTED-BY file respectively.  These
were not added to the glibc sources because they're not expected to be
of any use in future given that this is a one time task:

https://gist.github.com/siddhesh/b5ecac94eabfd72ed2916d6d8157e7dc
https://gist.github.com/siddhesh/15ea1f5e435ace9774f485030695ee02

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2021-09-03 22:06:44 +05:30

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/* Internal macros for atomic operations for GNU C Library.
Copyright (C) 2002-2021 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 _ATOMIC_H
#define _ATOMIC_H 1
/* This header defines three types of macros:
- atomic arithmetic and logic operation on memory. They all
have the prefix "atomic_".
- conditionally atomic operations of the same kinds. These
always behave identical but can be faster when atomicity
is not really needed since only one thread has access to
the memory location. In that case the code is slower in
the multi-thread case. The interfaces have the prefix
"catomic_".
- support functions like barriers. They also have the prefix
"atomic_".
Architectures must provide a few lowlevel macros (the compare
and exchange definitions). All others are optional. They
should only be provided if the architecture has specific
support for the operation.
As <atomic.h> macros are usually heavily nested and often use local
variables to make sure side-effects are evaluated properly, use for
macro local variables a per-macro unique prefix. This file uses
__atgN_ prefix where N is different in each macro. */
#include <stdlib.h>
#include <atomic-machine.h>
/* Wrapper macros to call pre_NN_post (mem, ...) where NN is the
bit width of *MEM. The calling macro puts parens around MEM
and following args. */
#define __atomic_val_bysize(pre, post, mem, ...) \
({ \
__typeof ((__typeof (*(mem))) *(mem)) __atg1_result; \
if (sizeof (*mem) == 1) \
__atg1_result = pre##_8_##post (mem, __VA_ARGS__); \
else if (sizeof (*mem) == 2) \
__atg1_result = pre##_16_##post (mem, __VA_ARGS__); \
else if (sizeof (*mem) == 4) \
__atg1_result = pre##_32_##post (mem, __VA_ARGS__); \
else if (sizeof (*mem) == 8) \
__atg1_result = pre##_64_##post (mem, __VA_ARGS__); \
else \
abort (); \
__atg1_result; \
})
#define __atomic_bool_bysize(pre, post, mem, ...) \
({ \
int __atg2_result; \
if (sizeof (*mem) == 1) \
__atg2_result = pre##_8_##post (mem, __VA_ARGS__); \
else if (sizeof (*mem) == 2) \
__atg2_result = pre##_16_##post (mem, __VA_ARGS__); \
else if (sizeof (*mem) == 4) \
__atg2_result = pre##_32_##post (mem, __VA_ARGS__); \
else if (sizeof (*mem) == 8) \
__atg2_result = pre##_64_##post (mem, __VA_ARGS__); \
else \
abort (); \
__atg2_result; \
})
/* Atomically store NEWVAL in *MEM if *MEM is equal to OLDVAL.
Return the old *MEM value. */
#if !defined atomic_compare_and_exchange_val_acq \
&& defined __arch_compare_and_exchange_val_32_acq
# define atomic_compare_and_exchange_val_acq(mem, newval, oldval) \
__atomic_val_bysize (__arch_compare_and_exchange_val,acq, \
mem, newval, oldval)
#endif
#ifndef catomic_compare_and_exchange_val_acq
# ifdef __arch_c_compare_and_exchange_val_32_acq
# define catomic_compare_and_exchange_val_acq(mem, newval, oldval) \
__atomic_val_bysize (__arch_c_compare_and_exchange_val,acq, \
mem, newval, oldval)
# else
# define catomic_compare_and_exchange_val_acq(mem, newval, oldval) \
atomic_compare_and_exchange_val_acq (mem, newval, oldval)
# endif
#endif
#ifndef catomic_compare_and_exchange_val_rel
# ifndef atomic_compare_and_exchange_val_rel
# define catomic_compare_and_exchange_val_rel(mem, newval, oldval) \
catomic_compare_and_exchange_val_acq (mem, newval, oldval)
# else
# define catomic_compare_and_exchange_val_rel(mem, newval, oldval) \
atomic_compare_and_exchange_val_rel (mem, newval, oldval)
# endif
#endif
#ifndef atomic_compare_and_exchange_val_rel
# define atomic_compare_and_exchange_val_rel(mem, newval, oldval) \
atomic_compare_and_exchange_val_acq (mem, newval, oldval)
#endif
/* Atomically store NEWVAL in *MEM if *MEM is equal to OLDVAL.
Return zero if *MEM was changed or non-zero if no exchange happened. */
#ifndef atomic_compare_and_exchange_bool_acq
# ifdef __arch_compare_and_exchange_bool_32_acq
# define atomic_compare_and_exchange_bool_acq(mem, newval, oldval) \
__atomic_bool_bysize (__arch_compare_and_exchange_bool,acq, \
mem, newval, oldval)
# else
# define atomic_compare_and_exchange_bool_acq(mem, newval, oldval) \
({ /* Cannot use __oldval here, because macros later in this file might \
call this macro with __oldval argument. */ \
__typeof (oldval) __atg3_old = (oldval); \
atomic_compare_and_exchange_val_acq (mem, newval, __atg3_old) \
!= __atg3_old; \
})
# endif
#endif
#ifndef catomic_compare_and_exchange_bool_acq
# ifdef __arch_c_compare_and_exchange_bool_32_acq
# define catomic_compare_and_exchange_bool_acq(mem, newval, oldval) \
__atomic_bool_bysize (__arch_c_compare_and_exchange_bool,acq, \
mem, newval, oldval)
# else
# define catomic_compare_and_exchange_bool_acq(mem, newval, oldval) \
({ /* Cannot use __oldval here, because macros later in this file might \
call this macro with __oldval argument. */ \
__typeof (oldval) __atg4_old = (oldval); \
catomic_compare_and_exchange_val_acq (mem, newval, __atg4_old) \
!= __atg4_old; \
})
# endif
#endif
/* Store NEWVALUE in *MEM and return the old value. */
#ifndef atomic_exchange_acq
# define atomic_exchange_acq(mem, newvalue) \
({ __typeof ((__typeof (*(mem))) *(mem)) __atg5_oldval; \
__typeof (mem) __atg5_memp = (mem); \
__typeof ((__typeof (*(mem))) *(mem)) __atg5_value = (newvalue); \
\
do \
__atg5_oldval = *__atg5_memp; \
while (__builtin_expect \
(atomic_compare_and_exchange_bool_acq (__atg5_memp, __atg5_value, \
__atg5_oldval), 0)); \
\
__atg5_oldval; })
#endif
#ifndef atomic_exchange_rel
# define atomic_exchange_rel(mem, newvalue) atomic_exchange_acq (mem, newvalue)
#endif
/* Add VALUE to *MEM and return the old value of *MEM. */
#ifndef atomic_exchange_and_add_acq
# ifdef atomic_exchange_and_add
# define atomic_exchange_and_add_acq(mem, value) \
atomic_exchange_and_add (mem, value)
# else
# define atomic_exchange_and_add_acq(mem, value) \
({ __typeof (*(mem)) __atg6_oldval; \
__typeof (mem) __atg6_memp = (mem); \
__typeof (*(mem)) __atg6_value = (value); \
\
do \
__atg6_oldval = *__atg6_memp; \
while (__builtin_expect \
(atomic_compare_and_exchange_bool_acq (__atg6_memp, \
__atg6_oldval \
+ __atg6_value, \
__atg6_oldval), 0)); \
\
__atg6_oldval; })
# endif
#endif
#ifndef atomic_exchange_and_add_rel
# define atomic_exchange_and_add_rel(mem, value) \
atomic_exchange_and_add_acq(mem, value)
#endif
#ifndef atomic_exchange_and_add
# define atomic_exchange_and_add(mem, value) \
atomic_exchange_and_add_acq(mem, value)
#endif
#ifndef catomic_exchange_and_add
# define catomic_exchange_and_add(mem, value) \
({ __typeof (*(mem)) __atg7_oldv; \
__typeof (mem) __atg7_memp = (mem); \
__typeof (*(mem)) __atg7_value = (value); \
\
do \
__atg7_oldv = *__atg7_memp; \
while (__builtin_expect \
(catomic_compare_and_exchange_bool_acq (__atg7_memp, \
__atg7_oldv \
+ __atg7_value, \
__atg7_oldv), 0)); \
\
__atg7_oldv; })
#endif
#ifndef atomic_max
# define atomic_max(mem, value) \
do { \
__typeof (*(mem)) __atg8_oldval; \
__typeof (mem) __atg8_memp = (mem); \
__typeof (*(mem)) __atg8_value = (value); \
do { \
__atg8_oldval = *__atg8_memp; \
if (__atg8_oldval >= __atg8_value) \
break; \
} while (__builtin_expect \
(atomic_compare_and_exchange_bool_acq (__atg8_memp, __atg8_value,\
__atg8_oldval), 0)); \
} while (0)
#endif
#ifndef catomic_max
# define catomic_max(mem, value) \
do { \
__typeof (*(mem)) __atg9_oldv; \
__typeof (mem) __atg9_memp = (mem); \
__typeof (*(mem)) __atg9_value = (value); \
do { \
__atg9_oldv = *__atg9_memp; \
if (__atg9_oldv >= __atg9_value) \
break; \
} while (__builtin_expect \
(catomic_compare_and_exchange_bool_acq (__atg9_memp, \
__atg9_value, \
__atg9_oldv), 0)); \
} while (0)
#endif
#ifndef atomic_min
# define atomic_min(mem, value) \
do { \
__typeof (*(mem)) __atg10_oldval; \
__typeof (mem) __atg10_memp = (mem); \
__typeof (*(mem)) __atg10_value = (value); \
do { \
__atg10_oldval = *__atg10_memp; \
if (__atg10_oldval <= __atg10_value) \
break; \
} while (__builtin_expect \
(atomic_compare_and_exchange_bool_acq (__atg10_memp, \
__atg10_value, \
__atg10_oldval), 0)); \
} while (0)
#endif
#ifndef atomic_add
# define atomic_add(mem, value) (void) atomic_exchange_and_add ((mem), (value))
#endif
#ifndef catomic_add
# define catomic_add(mem, value) \
(void) catomic_exchange_and_add ((mem), (value))
#endif
#ifndef atomic_increment
# define atomic_increment(mem) atomic_add ((mem), 1)
#endif
#ifndef catomic_increment
# define catomic_increment(mem) catomic_add ((mem), 1)
#endif
#ifndef atomic_increment_val
# define atomic_increment_val(mem) (atomic_exchange_and_add ((mem), 1) + 1)
#endif
#ifndef catomic_increment_val
# define catomic_increment_val(mem) (catomic_exchange_and_add ((mem), 1) + 1)
#endif
/* Add one to *MEM and return true iff it's now zero. */
#ifndef atomic_increment_and_test
# define atomic_increment_and_test(mem) \
(atomic_exchange_and_add ((mem), 1) + 1 == 0)
#endif
#ifndef atomic_decrement
# define atomic_decrement(mem) atomic_add ((mem), -1)
#endif
#ifndef catomic_decrement
# define catomic_decrement(mem) catomic_add ((mem), -1)
#endif
#ifndef atomic_decrement_val
# define atomic_decrement_val(mem) (atomic_exchange_and_add ((mem), -1) - 1)
#endif
#ifndef catomic_decrement_val
# define catomic_decrement_val(mem) (catomic_exchange_and_add ((mem), -1) - 1)
#endif
/* Subtract 1 from *MEM and return true iff it's now zero. */
#ifndef atomic_decrement_and_test
# define atomic_decrement_and_test(mem) \
(atomic_exchange_and_add ((mem), -1) == 1)
#endif
/* Decrement *MEM if it is > 0, and return the old value. */
#ifndef atomic_decrement_if_positive
# define atomic_decrement_if_positive(mem) \
({ __typeof (*(mem)) __atg11_oldval; \
__typeof (mem) __atg11_memp = (mem); \
\
do \
{ \
__atg11_oldval = *__atg11_memp; \
if (__glibc_unlikely (__atg11_oldval <= 0)) \
break; \
} \
while (__builtin_expect \
(atomic_compare_and_exchange_bool_acq (__atg11_memp, \
__atg11_oldval - 1, \
__atg11_oldval), 0)); \
__atg11_oldval; })
#endif
#ifndef atomic_add_negative
# define atomic_add_negative(mem, value) \
({ __typeof (value) __atg12_value = (value); \
atomic_exchange_and_add (mem, __atg12_value) < -__atg12_value; })
#endif
#ifndef atomic_add_zero
# define atomic_add_zero(mem, value) \
({ __typeof (value) __atg13_value = (value); \
atomic_exchange_and_add (mem, __atg13_value) == -__atg13_value; })
#endif
#ifndef atomic_bit_set
# define atomic_bit_set(mem, bit) \
(void) atomic_bit_test_set(mem, bit)
#endif
#ifndef atomic_bit_test_set
# define atomic_bit_test_set(mem, bit) \
({ __typeof (*(mem)) __atg14_old; \
__typeof (mem) __atg14_memp = (mem); \
__typeof (*(mem)) __atg14_mask = ((__typeof (*(mem))) 1 << (bit)); \
\
do \
__atg14_old = (*__atg14_memp); \
while (__builtin_expect \
(atomic_compare_and_exchange_bool_acq (__atg14_memp, \
__atg14_old | __atg14_mask,\
__atg14_old), 0)); \
\
__atg14_old & __atg14_mask; })
#endif
/* Atomically *mem &= mask. */
#ifndef atomic_and
# define atomic_and(mem, mask) \
do { \
__typeof (*(mem)) __atg15_old; \
__typeof (mem) __atg15_memp = (mem); \
__typeof (*(mem)) __atg15_mask = (mask); \
\
do \
__atg15_old = (*__atg15_memp); \
while (__builtin_expect \
(atomic_compare_and_exchange_bool_acq (__atg15_memp, \
__atg15_old & __atg15_mask, \
__atg15_old), 0)); \
} while (0)
#endif
#ifndef catomic_and
# define catomic_and(mem, mask) \
do { \
__typeof (*(mem)) __atg20_old; \
__typeof (mem) __atg20_memp = (mem); \
__typeof (*(mem)) __atg20_mask = (mask); \
\
do \
__atg20_old = (*__atg20_memp); \
while (__builtin_expect \
(catomic_compare_and_exchange_bool_acq (__atg20_memp, \
__atg20_old & __atg20_mask,\
__atg20_old), 0)); \
} while (0)
#endif
/* Atomically *mem &= mask and return the old value of *mem. */
#ifndef atomic_and_val
# define atomic_and_val(mem, mask) \
({ __typeof (*(mem)) __atg16_old; \
__typeof (mem) __atg16_memp = (mem); \
__typeof (*(mem)) __atg16_mask = (mask); \
\
do \
__atg16_old = (*__atg16_memp); \
while (__builtin_expect \
(atomic_compare_and_exchange_bool_acq (__atg16_memp, \
__atg16_old & __atg16_mask,\
__atg16_old), 0)); \
\
__atg16_old; })
#endif
/* Atomically *mem |= mask and return the old value of *mem. */
#ifndef atomic_or
# define atomic_or(mem, mask) \
do { \
__typeof (*(mem)) __atg17_old; \
__typeof (mem) __atg17_memp = (mem); \
__typeof (*(mem)) __atg17_mask = (mask); \
\
do \
__atg17_old = (*__atg17_memp); \
while (__builtin_expect \
(atomic_compare_and_exchange_bool_acq (__atg17_memp, \
__atg17_old | __atg17_mask, \
__atg17_old), 0)); \
} while (0)
#endif
#ifndef catomic_or
# define catomic_or(mem, mask) \
do { \
__typeof (*(mem)) __atg18_old; \
__typeof (mem) __atg18_memp = (mem); \
__typeof (*(mem)) __atg18_mask = (mask); \
\
do \
__atg18_old = (*__atg18_memp); \
while (__builtin_expect \
(catomic_compare_and_exchange_bool_acq (__atg18_memp, \
__atg18_old | __atg18_mask,\
__atg18_old), 0)); \
} while (0)
#endif
/* Atomically *mem |= mask and return the old value of *mem. */
#ifndef atomic_or_val
# define atomic_or_val(mem, mask) \
({ __typeof (*(mem)) __atg19_old; \
__typeof (mem) __atg19_memp = (mem); \
__typeof (*(mem)) __atg19_mask = (mask); \
\
do \
__atg19_old = (*__atg19_memp); \
while (__builtin_expect \
(atomic_compare_and_exchange_bool_acq (__atg19_memp, \
__atg19_old | __atg19_mask,\
__atg19_old), 0)); \
\
__atg19_old; })
#endif
#ifndef atomic_full_barrier
# define atomic_full_barrier() __asm ("" ::: "memory")
#endif
#ifndef atomic_read_barrier
# define atomic_read_barrier() atomic_full_barrier ()
#endif
#ifndef atomic_write_barrier
# define atomic_write_barrier() atomic_full_barrier ()
#endif
#ifndef atomic_forced_read
# define atomic_forced_read(x) \
({ __typeof (x) __x; __asm ("" : "=r" (__x) : "0" (x)); __x; })
#endif
/* This is equal to 1 iff the architecture supports 64b atomic operations. */
#ifndef __HAVE_64B_ATOMICS
#error Unable to determine if 64-bit atomics are present.
#endif
/* The following functions are a subset of the atomic operations provided by
C11. Usually, a function named atomic_OP_MO(args) is equivalent to C11's
atomic_OP_explicit(args, memory_order_MO); exceptions noted below. */
/* Each arch can request to use compiler built-ins for C11 atomics. If it
does, all atomics will be based on these. */
#if USE_ATOMIC_COMPILER_BUILTINS
/* We require 32b atomic operations; some archs also support 64b atomic
operations. */
void __atomic_link_error (void);
# if __HAVE_64B_ATOMICS == 1
# define __atomic_check_size(mem) \
if ((sizeof (*mem) != 4) && (sizeof (*mem) != 8)) \
__atomic_link_error ();
# else
# define __atomic_check_size(mem) \
if (sizeof (*mem) != 4) \
__atomic_link_error ();
# endif
/* We additionally provide 8b and 16b atomic loads and stores; we do not yet
need other atomic operations of such sizes, and restricting the support to
loads and stores makes this easier for archs that do not have native
support for atomic operations to less-than-word-sized data. */
# if __HAVE_64B_ATOMICS == 1
# define __atomic_check_size_ls(mem) \
if ((sizeof (*mem) != 1) && (sizeof (*mem) != 2) && (sizeof (*mem) != 4) \
&& (sizeof (*mem) != 8)) \
__atomic_link_error ();
# else
# define __atomic_check_size_ls(mem) \
if ((sizeof (*mem) != 1) && (sizeof (*mem) != 2) && sizeof (*mem) != 4) \
__atomic_link_error ();
# endif
# define atomic_thread_fence_acquire() \
__atomic_thread_fence (__ATOMIC_ACQUIRE)
# define atomic_thread_fence_release() \
__atomic_thread_fence (__ATOMIC_RELEASE)
# define atomic_thread_fence_seq_cst() \
__atomic_thread_fence (__ATOMIC_SEQ_CST)
# define atomic_load_relaxed(mem) \
({ __atomic_check_size_ls((mem)); \
__atomic_load_n ((mem), __ATOMIC_RELAXED); })
# define atomic_load_acquire(mem) \
({ __atomic_check_size_ls((mem)); \
__atomic_load_n ((mem), __ATOMIC_ACQUIRE); })
# define atomic_store_relaxed(mem, val) \
do { \
__atomic_check_size_ls((mem)); \
__atomic_store_n ((mem), (val), __ATOMIC_RELAXED); \
} while (0)
# define atomic_store_release(mem, val) \
do { \
__atomic_check_size_ls((mem)); \
__atomic_store_n ((mem), (val), __ATOMIC_RELEASE); \
} while (0)
/* On failure, this CAS has memory_order_relaxed semantics. */
# define atomic_compare_exchange_weak_relaxed(mem, expected, desired) \
({ __atomic_check_size((mem)); \
__atomic_compare_exchange_n ((mem), (expected), (desired), 1, \
__ATOMIC_RELAXED, __ATOMIC_RELAXED); })
# define atomic_compare_exchange_weak_acquire(mem, expected, desired) \
({ __atomic_check_size((mem)); \
__atomic_compare_exchange_n ((mem), (expected), (desired), 1, \
__ATOMIC_ACQUIRE, __ATOMIC_RELAXED); })
# define atomic_compare_exchange_weak_release(mem, expected, desired) \
({ __atomic_check_size((mem)); \
__atomic_compare_exchange_n ((mem), (expected), (desired), 1, \
__ATOMIC_RELEASE, __ATOMIC_RELAXED); })
# define atomic_exchange_relaxed(mem, desired) \
({ __atomic_check_size((mem)); \
__atomic_exchange_n ((mem), (desired), __ATOMIC_RELAXED); })
# define atomic_exchange_acquire(mem, desired) \
({ __atomic_check_size((mem)); \
__atomic_exchange_n ((mem), (desired), __ATOMIC_ACQUIRE); })
# define atomic_exchange_release(mem, desired) \
({ __atomic_check_size((mem)); \
__atomic_exchange_n ((mem), (desired), __ATOMIC_RELEASE); })
# define atomic_fetch_add_relaxed(mem, operand) \
({ __atomic_check_size((mem)); \
__atomic_fetch_add ((mem), (operand), __ATOMIC_RELAXED); })
# define atomic_fetch_add_acquire(mem, operand) \
({ __atomic_check_size((mem)); \
__atomic_fetch_add ((mem), (operand), __ATOMIC_ACQUIRE); })
# define atomic_fetch_add_release(mem, operand) \
({ __atomic_check_size((mem)); \
__atomic_fetch_add ((mem), (operand), __ATOMIC_RELEASE); })
# define atomic_fetch_add_acq_rel(mem, operand) \
({ __atomic_check_size((mem)); \
__atomic_fetch_add ((mem), (operand), __ATOMIC_ACQ_REL); })
# define atomic_fetch_and_relaxed(mem, operand) \
({ __atomic_check_size((mem)); \
__atomic_fetch_and ((mem), (operand), __ATOMIC_RELAXED); })
# define atomic_fetch_and_acquire(mem, operand) \
({ __atomic_check_size((mem)); \
__atomic_fetch_and ((mem), (operand), __ATOMIC_ACQUIRE); })
# define atomic_fetch_and_release(mem, operand) \
({ __atomic_check_size((mem)); \
__atomic_fetch_and ((mem), (operand), __ATOMIC_RELEASE); })
# define atomic_fetch_or_relaxed(mem, operand) \
({ __atomic_check_size((mem)); \
__atomic_fetch_or ((mem), (operand), __ATOMIC_RELAXED); })
# define atomic_fetch_or_acquire(mem, operand) \
({ __atomic_check_size((mem)); \
__atomic_fetch_or ((mem), (operand), __ATOMIC_ACQUIRE); })
# define atomic_fetch_or_release(mem, operand) \
({ __atomic_check_size((mem)); \
__atomic_fetch_or ((mem), (operand), __ATOMIC_RELEASE); })
# define atomic_fetch_xor_release(mem, operand) \
({ __atomic_check_size((mem)); \
__atomic_fetch_xor ((mem), (operand), __ATOMIC_RELEASE); })
#else /* !USE_ATOMIC_COMPILER_BUILTINS */
/* By default, we assume that read, write, and full barriers are equivalent
to acquire, release, and seq_cst barriers. Archs for which this does not
hold have to provide custom definitions of the fences. */
# ifndef atomic_thread_fence_acquire
# define atomic_thread_fence_acquire() atomic_read_barrier ()
# endif
# ifndef atomic_thread_fence_release
# define atomic_thread_fence_release() atomic_write_barrier ()
# endif
# ifndef atomic_thread_fence_seq_cst
# define atomic_thread_fence_seq_cst() atomic_full_barrier ()
# endif
# ifndef atomic_load_relaxed
# define atomic_load_relaxed(mem) \
({ __typeof ((__typeof (*(mem))) *(mem)) __atg100_val; \
__asm ("" : "=r" (__atg100_val) : "0" (*(mem))); \
__atg100_val; })
# endif
# ifndef atomic_load_acquire
# define atomic_load_acquire(mem) \
({ __typeof (*(mem)) __atg101_val = atomic_load_relaxed (mem); \
atomic_thread_fence_acquire (); \
__atg101_val; })
# endif
# ifndef atomic_store_relaxed
/* XXX Use inline asm here? */
# define atomic_store_relaxed(mem, val) do { *(mem) = (val); } while (0)
# endif
# ifndef atomic_store_release
# define atomic_store_release(mem, val) \
do { \
atomic_thread_fence_release (); \
atomic_store_relaxed ((mem), (val)); \
} while (0)
# endif
/* On failure, this CAS has memory_order_relaxed semantics. */
/* XXX This potentially has one branch more than necessary, but archs
currently do not define a CAS that returns both the previous value and
the success flag. */
# ifndef atomic_compare_exchange_weak_acquire
# define atomic_compare_exchange_weak_acquire(mem, expected, desired) \
({ typeof (*(expected)) __atg102_expected = *(expected); \
*(expected) = \
atomic_compare_and_exchange_val_acq ((mem), (desired), *(expected)); \
*(expected) == __atg102_expected; })
# endif
# ifndef atomic_compare_exchange_weak_relaxed
/* XXX Fall back to CAS with acquire MO because archs do not define a weaker
CAS. */
# define atomic_compare_exchange_weak_relaxed(mem, expected, desired) \
atomic_compare_exchange_weak_acquire ((mem), (expected), (desired))
# endif
# ifndef atomic_compare_exchange_weak_release
# define atomic_compare_exchange_weak_release(mem, expected, desired) \
({ typeof (*(expected)) __atg103_expected = *(expected); \
*(expected) = \
atomic_compare_and_exchange_val_rel ((mem), (desired), *(expected)); \
*(expected) == __atg103_expected; })
# endif
/* XXX Fall back to acquire MO because archs do not define a weaker
atomic_exchange. */
# ifndef atomic_exchange_relaxed
# define atomic_exchange_relaxed(mem, val) \
atomic_exchange_acq ((mem), (val))
# endif
# ifndef atomic_exchange_acquire
# define atomic_exchange_acquire(mem, val) \
atomic_exchange_acq ((mem), (val))
# endif
# ifndef atomic_exchange_release
# define atomic_exchange_release(mem, val) \
atomic_exchange_rel ((mem), (val))
# endif
# ifndef atomic_fetch_add_acquire
# define atomic_fetch_add_acquire(mem, operand) \
atomic_exchange_and_add_acq ((mem), (operand))
# endif
# ifndef atomic_fetch_add_relaxed
/* XXX Fall back to acquire MO because the MO semantics of
atomic_exchange_and_add are not documented; the generic version falls back
to atomic_exchange_and_add_acq if atomic_exchange_and_add is not defined,
and vice versa. */
# define atomic_fetch_add_relaxed(mem, operand) \
atomic_fetch_add_acquire ((mem), (operand))
# endif
# ifndef atomic_fetch_add_release
# define atomic_fetch_add_release(mem, operand) \
atomic_exchange_and_add_rel ((mem), (operand))
# endif
# ifndef atomic_fetch_add_acq_rel
# define atomic_fetch_add_acq_rel(mem, operand) \
({ atomic_thread_fence_release (); \
atomic_exchange_and_add_acq ((mem), (operand)); })
# endif
/* XXX Fall back to acquire MO because archs do not define a weaker
atomic_and_val. */
# ifndef atomic_fetch_and_relaxed
# define atomic_fetch_and_relaxed(mem, operand) \
atomic_fetch_and_acquire ((mem), (operand))
# endif
/* XXX The default for atomic_and_val has acquire semantics, but this is not
documented. */
# ifndef atomic_fetch_and_acquire
# define atomic_fetch_and_acquire(mem, operand) \
atomic_and_val ((mem), (operand))
# endif
# ifndef atomic_fetch_and_release
/* XXX This unnecessarily has acquire MO. */
# define atomic_fetch_and_release(mem, operand) \
({ atomic_thread_fence_release (); \
atomic_and_val ((mem), (operand)); })
# endif
/* XXX The default for atomic_or_val has acquire semantics, but this is not
documented. */
# ifndef atomic_fetch_or_acquire
# define atomic_fetch_or_acquire(mem, operand) \
atomic_or_val ((mem), (operand))
# endif
/* XXX Fall back to acquire MO because archs do not define a weaker
atomic_or_val. */
# ifndef atomic_fetch_or_relaxed
# define atomic_fetch_or_relaxed(mem, operand) \
atomic_fetch_or_acquire ((mem), (operand))
# endif
/* XXX Contains an unnecessary acquire MO because archs do not define a weaker
atomic_or_val. */
# ifndef atomic_fetch_or_release
# define atomic_fetch_or_release(mem, operand) \
({ atomic_thread_fence_release (); \
atomic_fetch_or_acquire ((mem), (operand)); })
# endif
# ifndef atomic_fetch_xor_release
/* Failing the atomic_compare_exchange_weak_release reloads the value in
__atg104_expected, so we need only do the XOR again and retry. */
# define atomic_fetch_xor_release(mem, operand) \
({ __typeof (mem) __atg104_memp = (mem); \
__typeof (*(mem)) __atg104_expected = (*__atg104_memp); \
__typeof (*(mem)) __atg104_desired; \
__typeof (*(mem)) __atg104_op = (operand); \
\
do \
__atg104_desired = __atg104_expected ^ __atg104_op; \
while (__glibc_unlikely \
(atomic_compare_exchange_weak_release ( \
__atg104_memp, &__atg104_expected, __atg104_desired) \
== 0)); \
__atg104_expected; })
#endif
#endif /* !USE_ATOMIC_COMPILER_BUILTINS */
/* This operation does not affect synchronization semantics but can be used
in the body of a spin loop to potentially improve its efficiency. */
#ifndef atomic_spin_nop
# define atomic_spin_nop() do { /* nothing */ } while (0)
#endif
/* ATOMIC_EXCHANGE_USES_CAS is non-zero if atomic_exchange operations
are implemented based on a CAS loop; otherwise, this is zero and we assume
that the atomic_exchange operations could provide better performance
than a CAS loop. */
#ifndef ATOMIC_EXCHANGE_USES_CAS
# error ATOMIC_EXCHANGE_USES_CAS has to be defined.
#endif
#endif /* atomic.h */
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