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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 | * | |
9 | * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> | |
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 | */ | |
2dc5fa0f | 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 | ||
ec4e58a3 | 50 | #endif /* _URCU_COMPILER_H */ |