src/atomic/SDL_atomic.c
author Sam Lantinga <slouken@libsdl.org>
Tue, 26 May 2015 06:27:46 -0700
changeset 9619 b94b6d0bff0f
parent 8979 1e283b7a1580
child 9998 f67cf37e9cd4
permissions -rw-r--r--
Updated the copyright year to 2015
     1 /*
     2   Simple DirectMedia Layer
     3   Copyright (C) 1997-2015 Sam Lantinga <slouken@libsdl.org>
     4 
     5   This software is provided 'as-is', without any express or implied
     6   warranty.  In no event will the authors be held liable for any damages
     7   arising from the use of this software.
     8 
     9   Permission is granted to anyone to use this software for any purpose,
    10   including commercial applications, and to alter it and redistribute it
    11   freely, subject to the following restrictions:
    12 
    13   1. The origin of this software must not be misrepresented; you must not
    14      claim that you wrote the original software. If you use this software
    15      in a product, an acknowledgment in the product documentation would be
    16      appreciated but is not required.
    17   2. Altered source versions must be plainly marked as such, and must not be
    18      misrepresented as being the original software.
    19   3. This notice may not be removed or altered from any source distribution.
    20 */
    21 #include "../SDL_internal.h"
    22 
    23 #include "SDL_atomic.h"
    24 
    25 #if defined(_MSC_VER) && (_MSC_VER >= 1500)
    26 #include <intrin.h>
    27 #define HAVE_MSC_ATOMICS 1
    28 #endif
    29 
    30 #if defined(__MACOSX__)  /* !!! FIXME: should we favor gcc atomics? */
    31 #include <libkern/OSAtomic.h>
    32 #endif
    33 
    34 #if !defined(HAVE_GCC_ATOMICS) && defined(__SOLARIS__)
    35 #include <atomic.h>
    36 #endif
    37 
    38 /*
    39   If any of the operations are not provided then we must emulate some
    40   of them. That means we need a nice implementation of spin locks
    41   that avoids the "one big lock" problem. We use a vector of spin
    42   locks and pick which one to use based on the address of the operand
    43   of the function.
    44 
    45   To generate the index of the lock we first shift by 3 bits to get
    46   rid on the zero bits that result from 32 and 64 bit allignment of
    47   data. We then mask off all but 5 bits and use those 5 bits as an
    48   index into the table.
    49 
    50   Picking the lock this way insures that accesses to the same data at
    51   the same time will go to the same lock. OTOH, accesses to different
    52   data have only a 1/32 chance of hitting the same lock. That should
    53   pretty much eliminate the chances of several atomic operations on
    54   different data from waiting on the same "big lock". If it isn't
    55   then the table of locks can be expanded to a new size so long as
    56   the new size is a power of two.
    57 
    58   Contributed by Bob Pendleton, bob@pendleton.com
    59 */
    60 
    61 #if !defined(HAVE_MSC_ATOMICS) && !defined(HAVE_GCC_ATOMICS) && !defined(__MACOSX__) && !defined(__SOLARIS__)
    62 #define EMULATE_CAS 1
    63 #endif
    64 
    65 #if EMULATE_CAS
    66 static SDL_SpinLock locks[32];
    67 
    68 static SDL_INLINE void
    69 enterLock(void *a)
    70 {
    71     uintptr_t index = ((((uintptr_t)a) >> 3) & 0x1f);
    72 
    73     SDL_AtomicLock(&locks[index]);
    74 }
    75 
    76 static SDL_INLINE void
    77 leaveLock(void *a)
    78 {
    79     uintptr_t index = ((((uintptr_t)a) >> 3) & 0x1f);
    80 
    81     SDL_AtomicUnlock(&locks[index]);
    82 }
    83 #endif
    84 
    85 
    86 SDL_bool
    87 SDL_AtomicCAS(SDL_atomic_t *a, int oldval, int newval)
    88 {
    89 #ifdef HAVE_MSC_ATOMICS
    90     return (_InterlockedCompareExchange((long*)&a->value, (long)newval, (long)oldval) == (long)oldval);
    91 #elif defined(__MACOSX__)  /* !!! FIXME: should we favor gcc atomics? */
    92     return (SDL_bool) OSAtomicCompareAndSwap32Barrier(oldval, newval, &a->value);
    93 #elif defined(HAVE_GCC_ATOMICS)
    94     return (SDL_bool) __sync_bool_compare_and_swap(&a->value, oldval, newval);
    95 #elif defined(__SOLARIS__) && defined(_LP64)
    96     return (SDL_bool) ((int) atomic_cas_64((volatile uint64_t*)&a->value, (uint64_t)oldval, (uint64_t)newval) == oldval);
    97 #elif defined(__SOLARIS__) && !defined(_LP64)
    98     return (SDL_bool) ((int) atomic_cas_32((volatile uint32_t*)&a->value, (uint32_t)oldval, (uint32_t)newval) == oldval);
    99 #elif EMULATE_CAS
   100     SDL_bool retval = SDL_FALSE;
   101 
   102     enterLock(a);
   103     if (a->value == oldval) {
   104         a->value = newval;
   105         retval = SDL_TRUE;
   106     }
   107     leaveLock(a);
   108 
   109     return retval;
   110 #else
   111     #error Please define your platform.
   112 #endif
   113 }
   114 
   115 SDL_bool
   116 SDL_AtomicCASPtr(void **a, void *oldval, void *newval)
   117 {
   118 #if defined(HAVE_MSC_ATOMICS) && (_M_IX86)
   119     return (_InterlockedCompareExchange((long*)a, (long)newval, (long)oldval) == (long)oldval);
   120 #elif defined(HAVE_MSC_ATOMICS) && (!_M_IX86)
   121     return (_InterlockedCompareExchangePointer(a, newval, oldval) == oldval);
   122 #elif defined(__MACOSX__) && defined(__LP64__)   /* !!! FIXME: should we favor gcc atomics? */
   123     return (SDL_bool) OSAtomicCompareAndSwap64Barrier((int64_t)oldval, (int64_t)newval, (int64_t*) a);
   124 #elif defined(__MACOSX__) && !defined(__LP64__)  /* !!! FIXME: should we favor gcc atomics? */
   125     return (SDL_bool) OSAtomicCompareAndSwap32Barrier((int32_t)oldval, (int32_t)newval, (int32_t*) a);
   126 #elif defined(HAVE_GCC_ATOMICS)
   127     return __sync_bool_compare_and_swap(a, oldval, newval);
   128 #elif defined(__SOLARIS__)
   129     return (SDL_bool) (atomic_cas_ptr(a, oldval, newval) == oldval);
   130 #elif EMULATE_CAS
   131     SDL_bool retval = SDL_FALSE;
   132 
   133     enterLock(a);
   134     if (*a == oldval) {
   135         *a = newval;
   136         retval = SDL_TRUE;
   137     }
   138     leaveLock(a);
   139 
   140     return retval;
   141 #else
   142     #error Please define your platform.
   143 #endif
   144 }
   145 
   146 int
   147 SDL_AtomicSet(SDL_atomic_t *a, int v)
   148 {
   149 #ifdef HAVE_MSC_ATOMICS
   150     return _InterlockedExchange((long*)&a->value, v);
   151 #elif defined(HAVE_GCC_ATOMICS)
   152     return __sync_lock_test_and_set(&a->value, v);
   153 #elif defined(__SOLARIS__) && defined(_LP64)
   154     return (int) atomic_swap_64((volatile uint64_t*)&a->value, (uint64_t)v);
   155 #elif defined(__SOLARIS__) && !defined(_LP64)
   156     return (int) atomic_swap_32((volatile uint32_t*)&a->value, (uint32_t)v);
   157 #else
   158     int value;
   159     do {
   160         value = a->value;
   161     } while (!SDL_AtomicCAS(a, value, v));
   162     return value;
   163 #endif
   164 }
   165 
   166 void*
   167 SDL_AtomicSetPtr(void **a, void *v)
   168 {
   169 #if defined(HAVE_MSC_ATOMICS) && (_M_IX86)
   170     return (void *) _InterlockedExchange((long *)a, (long) v);
   171 #elif defined(HAVE_MSC_ATOMICS) && (!_M_IX86)
   172     return _InterlockedExchangePointer(a, v);
   173 #elif defined(HAVE_GCC_ATOMICS)
   174     return __sync_lock_test_and_set(a, v);
   175 #elif defined(__SOLARIS__)
   176     return atomic_swap_ptr(a, v);
   177 #else
   178     void *value;
   179     do {
   180         value = *a;
   181     } while (!SDL_AtomicCASPtr(a, value, v));
   182     return value;
   183 #endif
   184 }
   185 
   186 int
   187 SDL_AtomicAdd(SDL_atomic_t *a, int v)
   188 {
   189 #ifdef HAVE_MSC_ATOMICS
   190     return _InterlockedExchangeAdd((long*)&a->value, v);
   191 #elif defined(HAVE_GCC_ATOMICS)
   192     return __sync_fetch_and_add(&a->value, v);
   193 #elif defined(__SOLARIS__)
   194     int pv = a->value;
   195     membar_consumer();
   196 #if defined(_LP64)
   197     atomic_add_64((volatile uint64_t*)&a->value, v);
   198 #elif !defined(_LP64)
   199     atomic_add_32((volatile uint32_t*)&a->value, v);
   200 #endif
   201     return pv;
   202 #else
   203     int value;
   204     do {
   205         value = a->value;
   206     } while (!SDL_AtomicCAS(a, value, (value + v)));
   207     return value;
   208 #endif
   209 }
   210 
   211 int
   212 SDL_AtomicGet(SDL_atomic_t *a)
   213 {
   214     int value;
   215     do {
   216         value = a->value;
   217     } while (!SDL_AtomicCAS(a, value, value));
   218     return value;
   219 }
   220 
   221 void *
   222 SDL_AtomicGetPtr(void **a)
   223 {
   224     void *value;
   225     do {
   226         value = *a;
   227     } while (!SDL_AtomicCASPtr(a, value, value));
   228     return value;
   229 }
   230 
   231 #ifdef __thumb__
   232 #if defined(__ARM_ARCH_6__) || defined(__ARM_ARCH_6J__) || defined(__ARM_ARCH_6K__) || defined(__ARM_ARCH_6T2__) || defined(__ARM_ARCH_6Z__) || defined(__ARM_ARCH_6ZK__)
   233 __asm__(
   234 "   .align 2\n"
   235 "   .globl _SDL_MemoryBarrierRelease\n"
   236 "   .globl _SDL_MemoryBarrierAcquire\n"
   237 "_SDL_MemoryBarrierRelease:\n"
   238 "_SDL_MemoryBarrierAcquire:\n"
   239 "   mov r0, #0\n"
   240 "   mcr p15, 0, r0, c7, c10, 5\n"
   241 "   bx lr\n"
   242 );
   243 #endif
   244 #endif
   245 
   246 /* vi: set ts=4 sw=4 expandtab: */