Update version to 0.4.6
[urcu.git] / urcu / compiler.h
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1#ifndef _URCU_COMPILER_H
2#define _URCU_COMPILER_H
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3
4/*
5 * compiler.h
6 *
7 * Compiler definitions.
8 *
6982d6d7 9 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
af02d47e 10 *
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11 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
12 * OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
af02d47e 13 *
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14 * Permission is hereby granted to use or copy this program
15 * for any purpose, provided the above notices are retained on all copies.
16 * Permission to modify the code and to distribute modified code is granted,
17 * provided the above notices are retained, and a notice that the code was
18 * modified is included with the above copyright notice.
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19 */
20
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21#include <stddef.h> /* for offsetof */
22
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23#define likely(x) __builtin_expect(!!(x), 1)
24#define unlikely(x) __builtin_expect(!!(x), 0)
2dc5fa0f 25
f540a0fd 26#define barrier() asm volatile("" : : : "memory")
2dc5fa0f 27
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28/*
29 * Instruct the compiler to perform only a single access to a variable
30 * (prohibits merging and refetching). The compiler is also forbidden to reorder
31 * successive instances of ACCESS_ONCE(), but only when the compiler is aware of
32 * particular ordering. Compiler ordering can be ensured, for example, by
33 * putting two ACCESS_ONCE() in separate C statements.
34 *
35 * This macro does absolutely -nothing- to prevent the CPU from reordering,
36 * merging, or refetching absolutely anything at any time. Its main intended
37 * use is to mediate communication between process-level code and irq/NMI
38 * handlers, all running on the same CPU.
39 */
56b14eae 40#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
af02d47e 41
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42#ifndef max
43#define max(a,b) ((a)>(b)?(a):(b))
44#endif
45
46#ifndef min
47#define min(a,b) ((a)<(b)?(a):(b))
48#endif
49
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50#if defined(__SIZEOF_LONG__)
51#define BITS_PER_LONG (__SIZEOF_LONG__ * 8)
52#elif defined(_LP64)
53#define BITS_PER_LONG 64
54#else
55#define BITS_PER_LONG 32
56#endif
57
ec4e58a3 58#endif /* _URCU_COMPILER_H */
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