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      1 /* Copyright (c) 2013, Ben Noordhuis <info (at) bnoordhuis.nl>
      2  *
      3  * Permission to use, copy, modify, and/or distribute this software for any
      4  * purpose with or without fee is hereby granted, provided that the above
      5  * copyright notice and this permission notice appear in all copies.
      6  *
      7  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
      8  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
      9  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
     10  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
     11  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
     12  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
     13  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
     14  */
     15 
     16 #ifndef UV_ATOMIC_OPS_H_
     17 #define UV_ATOMIC_OPS_H_
     18 
     19 #include "internal.h"  /* UV_UNUSED */
     20 
     21 #if defined(__SUNPRO_C) || defined(__SUNPRO_CC)
     22 #include <atomic.h>
     23 #endif
     24 
     25 UV_UNUSED(static int cmpxchgi(int* ptr, int oldval, int newval));
     26 UV_UNUSED(static void cpu_relax(void));
     27 
     28 /* Prefer hand-rolled assembly over the gcc builtins because the latter also
     29  * issue full memory barriers.
     30  */
     31 UV_UNUSED(static int cmpxchgi(int* ptr, int oldval, int newval)) {
     32 #if defined(__i386__) || defined(__x86_64__)
     33   int out;
     34   __asm__ __volatile__ ("lock; cmpxchg %2, %1;"
     35                         : "=a" (out), "+m" (*(volatile int*) ptr)
     36                         : "r" (newval), "0" (oldval)
     37                         : "memory");
     38   return out;
     39 #elif defined(__MVS__)
     40   /* Use hand-rolled assembly because codegen from builtin __plo_CSST results in
     41    * a runtime bug.
     42    */
     43   __asm(" cs %0,%2,%1 \n " : "+r"(oldval), "+m"(*ptr) : "r"(newval) :);
     44   return oldval;
     45 #elif defined(__SUNPRO_C) || defined(__SUNPRO_CC)
     46   return atomic_cas_uint((uint_t *)ptr, (uint_t)oldval, (uint_t)newval);
     47 #else
     48   return __sync_val_compare_and_swap(ptr, oldval, newval);
     49 #endif
     50 }
     51 
     52 UV_UNUSED(static void cpu_relax(void)) {
     53 #if defined(__i386__) || defined(__x86_64__)
     54   __asm__ __volatile__ ("rep; nop" ::: "memory");  /* a.k.a. PAUSE */
     55 #elif (defined(__arm__) && __ARM_ARCH >= 7) || defined(__aarch64__)
     56   __asm__ __volatile__ ("yield" ::: "memory");
     57 #elif (defined(__ppc__) || defined(__ppc64__)) && defined(__APPLE__)
     58   __asm volatile ("" : : : "memory");
     59 #elif !defined(__APPLE__) && (defined(__powerpc64__) || defined(__ppc64__) || defined(__PPC64__))
     60   __asm__ __volatile__ ("or 1,1,1; or 2,2,2" ::: "memory");
     61 #endif
     62 }
     63 
     64 #endif  /* UV_ATOMIC_OPS_H_ */
     65