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Kitware
GitHub Repository: Kitware/CMake
 Path: blob/master/Utilities/cmlibuv/src/unix/atomic-ops.h
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/* Copyright (c) 2013, Ben Noordhuis <[email protected]>

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 *

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 * Permission to use, copy, modify, and/or distribute this software for any

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 * purpose with or without fee is hereby granted, provided that the above

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 * copyright notice and this permission notice appear in all copies.

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 *

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 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES

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 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF

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 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR

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 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES

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 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN

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 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF

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 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

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 */

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#ifndef UV_ATOMIC_OPS_H_

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#define UV_ATOMIC_OPS_H_

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#include "internal.h"  /* UV_UNUSED */

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#if defined(__SUNPRO_C) || defined(__SUNPRO_CC)

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#include <atomic.h>

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#endif

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UV_UNUSED(static int cmpxchgi(int* ptr, int oldval, int newval));

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UV_UNUSED(static void cpu_relax(void));

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/* Prefer hand-rolled assembly over the gcc builtins because the latter also

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 * issue full memory barriers.

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 */

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UV_UNUSED(static int cmpxchgi(int* ptr, int oldval, int newval)) {

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#if defined(__i386__) || defined(__x86_64__)

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  int out;

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  __asm__ __volatile__ ("lock; cmpxchg %2, %1;"

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                        : "=a" (out), "+m" (*(volatile int*) ptr)

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                        : "r" (newval), "0" (oldval)

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                        : "memory");

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  return out;

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#elif defined(_AIX) && defined(__ibmxl__)

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  /* FIXME: This is not actually atomic but XLClang 16.1 for AIX

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     does not provide __sync_val_compare_and_swap or an equivalent.

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     Its documentation suggests using C++11 atomics but this is C.  */

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  __compare_and_swap((volatile int*)ptr, &oldval, newval);

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  return oldval;

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#elif defined(__MVS__)

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  /* Use hand-rolled assembly because codegen from builtin __plo_CSST results in

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   * a runtime bug.

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   */

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  __asm(" cs %0,%2,%1 \n " : "+r"(oldval), "+m"(*ptr) : "r"(newval) :);

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  return oldval;

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#elif defined(__SUNPRO_C) || defined(__SUNPRO_CC)

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  return atomic_cas_uint((uint_t *)ptr, (uint_t)oldval, (uint_t)newval);

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#else

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  return __sync_val_compare_and_swap(ptr, oldval, newval);

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#endif

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}

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UV_UNUSED(static void cpu_relax(void)) {

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#if defined(__i386__) || defined(__x86_64__)

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  __asm__ __volatile__ ("rep; nop" ::: "memory");  /* a.k.a. PAUSE */

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#elif (defined(__arm__) && __ARM_ARCH >= 7) || defined(__aarch64__)

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  __asm__ __volatile__ ("yield" ::: "memory");

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#elif (defined(__ppc__) || defined(__ppc64__)) && defined(__APPLE__)

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  __asm volatile ("" : : : "memory");

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#elif !defined(__APPLE__) && (defined(__powerpc64__) || defined(__ppc64__) || defined(__PPC64__))

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  __asm__ __volatile__ ("or 1,1,1; or 2,2,2" ::: "memory");

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#endif

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}

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#endif  /* UV_ATOMIC_OPS_H_ */

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