PortAudio  2.0
pa_memorybarrier.h
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1 /*
2  * $Id: pa_memorybarrier.h 1240 2007-07-17 13:05:07Z bjornroche $
3  * Portable Audio I/O Library
4  * Memory barrier utilities
5  *
6  * Author: Bjorn Roche, XO Audio, LLC
7  *
8  * This program uses the PortAudio Portable Audio Library.
9  * For more information see: http://www.portaudio.com
10  * Copyright (c) 1999-2000 Ross Bencina and Phil Burk
11  *
12  * Permission is hereby granted, free of charge, to any person obtaining
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14  * (the "Software"), to deal in the Software without restriction,
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31 
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42 
48 /****************
49  * Some memory barrier primitives based on the system.
50  * right now only OS X, FreeBSD, and Linux are supported. In addition to providing
51  * memory barriers, these functions should ensure that data cached in registers
52  * is written out to cache where it can be snooped by other CPUs. (ie, the volatile
53  * keyword should not be required)
54  *
55  * the primitives that must be defined are:
56  *
57  * PaUtil_FullMemoryBarrier()
58  * PaUtil_ReadMemoryBarrier()
59  * PaUtil_WriteMemoryBarrier()
60  *
61  ****************/
62 
63 #if defined(__APPLE__)
64 # include <libkern/OSAtomic.h>
65  /* Here are the memory barrier functions. Mac OS X only provides
66  full memory barriers, so the three types of barriers are the same,
67  however, these barriers are superior to compiler-based ones. */
68 # define PaUtil_FullMemoryBarrier() OSMemoryBarrier()
69 # define PaUtil_ReadMemoryBarrier() OSMemoryBarrier()
70 # define PaUtil_WriteMemoryBarrier() OSMemoryBarrier()
71 #elif defined(__GNUC__)
72  /* GCC >= 4.1 has built-in intrinsics. We'll use those */
73 # if (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 1)
74 # define PaUtil_FullMemoryBarrier() __sync_synchronize()
75 # define PaUtil_ReadMemoryBarrier() __sync_synchronize()
76 # define PaUtil_WriteMemoryBarrier() __sync_synchronize()
77  /* as a fallback, GCC understands volatile asm and "memory" to mean it
78  * should not reorder memory read/writes */
79  /* Note that it is not clear that any compiler actually defines __PPC__,
80  * it can probably removed safely. */
81 # elif defined( __ppc__ ) || defined( __powerpc__) || defined( __PPC__ )
82 # define PaUtil_FullMemoryBarrier() asm volatile("sync":::"memory")
83 # define PaUtil_ReadMemoryBarrier() asm volatile("sync":::"memory")
84 # define PaUtil_WriteMemoryBarrier() asm volatile("sync":::"memory")
85 # elif defined( __i386__ ) || defined( __i486__ ) || defined( __i586__ ) || \
86  defined( __i686__ ) || defined( __x86_64__ )
87 # define PaUtil_FullMemoryBarrier() asm volatile("mfence":::"memory")
88 # define PaUtil_ReadMemoryBarrier() asm volatile("lfence":::"memory")
89 # define PaUtil_WriteMemoryBarrier() asm volatile("sfence":::"memory")
90 # else
91 # ifdef ALLOW_SMP_DANGERS
92 # warning Memory barriers not defined on this system or system unknown
93 # warning For SMP safety, you should fix this.
94 # define PaUtil_FullMemoryBarrier()
95 # define PaUtil_ReadMemoryBarrier()
96 # define PaUtil_WriteMemoryBarrier()
97 # else
98 # error Memory barriers are not defined on this system. You can still compile by defining ALLOW_SMP_DANGERS, but SMP safety will not be guaranteed.
99 # endif
100 # endif
101 #elif (_MSC_VER >= 1400) && !defined(_WIN32_WCE)
102 # include <intrin.h>
103 # pragma intrinsic(_ReadWriteBarrier)
104 # pragma intrinsic(_ReadBarrier)
105 # pragma intrinsic(_WriteBarrier)
106 /* note that MSVC intrinsics _ReadWriteBarrier(), _ReadBarrier(), _WriteBarrier() are just compiler barriers *not* memory barriers */
107 # define PaUtil_FullMemoryBarrier() _ReadWriteBarrier()
108 # define PaUtil_ReadMemoryBarrier() _ReadBarrier()
109 # define PaUtil_WriteMemoryBarrier() _WriteBarrier()
110 #elif defined(_WIN32_WCE)
111 # define PaUtil_FullMemoryBarrier()
112 # define PaUtil_ReadMemoryBarrier()
113 # define PaUtil_WriteMemoryBarrier()
114 #elif defined(_MSC_VER) || defined(__BORLANDC__)
115 # define PaUtil_FullMemoryBarrier() _asm { lock add [esp], 0 }
116 # define PaUtil_ReadMemoryBarrier() _asm { lock add [esp], 0 }
117 # define PaUtil_WriteMemoryBarrier() _asm { lock add [esp], 0 }
118 #else
119 # ifdef ALLOW_SMP_DANGERS
120 # warning Memory barriers not defined on this system or system unknown
121 # warning For SMP safety, you should fix this.
122 # define PaUtil_FullMemoryBarrier()
123 # define PaUtil_ReadMemoryBarrier()
124 # define PaUtil_WriteMemoryBarrier()
125 # else
126 # error Memory barriers are not defined on this system. You can still compile by defining ALLOW_SMP_DANGERS, but SMP safety will not be guaranteed.
127 # endif
128 #endif
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