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/*
* Copyright (C) Internet Systems Consortium, Inc. ("ISC")
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*
* See the COPYRIGHT file distributed with this work for additional
* information regarding copyright ownership.
*/
#ifndef ISC_ATOMIC_H
#define ISC_ATOMIC_H 1
#include <inttypes.h>
#include <isc/platform.h>
#include <isc/types.h>
#ifdef ISC_PLATFORM_USEGCCASM
/*
* This routine atomically increments the value stored in 'p' by 'val', and
* returns the previous value.
*
* Open issue: can 'fetchadd' make the code faster for some particular values
* (e.g., 1 and -1)?
*/
static inline int32_t
#ifdef __GNUC__
__attribute__ ((unused))
#endif
isc_atomic_xadd(int32_t *p, int32_t val)
{
int32_t prev, swapped;
for (prev = *(volatile int32_t *)p; ; prev = swapped) {
swapped = prev + val;
__asm__ volatile(
"mov ar.ccv=%2;;"
"cmpxchg4.acq %0=%4,%3,ar.ccv"
: "=r" (swapped), "=m" (*p)
: "r" (prev), "r" (swapped), "m" (*p)
: "memory");
if (swapped == prev)
break;
}
return (prev);
}
/*
* This routine atomically stores the value 'val' in 'p'.
*/
static inline void
#ifdef __GNUC__
__attribute__ ((unused))
#endif
isc_atomic_store(int32_t *p, int32_t val)
{
__asm__ volatile(
"st4.rel %0=%1"
: "=m" (*p)
: "r" (val)
: "memory"
);
}
/*
* This routine atomically replaces the value in 'p' with 'val', if the
* original value is equal to 'cmpval'. The original value is returned in any
* case.
*/
static inline int32_t
#ifdef __GNUC__
__attribute__ ((unused))
#endif
isc_atomic_cmpxchg(int32_t *p, int32_t cmpval, int32_t val)
{
int32_t ret;
__asm__ volatile(
"mov ar.ccv=%2;;"
"cmpxchg4.acq %0=%4,%3,ar.ccv"
: "=r" (ret), "=m" (*p)
: "r" (cmpval), "r" (val), "m" (*p)
: "memory");
return (ret);
}
#else /* !ISC_PLATFORM_USEGCCASM */
#error "unsupported compiler. disable atomic ops by --disable-atomic"
#endif
#endif /* ISC_ATOMIC_H */
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