urcu/compiler.h

   1 #ifndef _URCU_COMPILER_H
   2 #define _URCU_COMPILER_H
   3
   4 /*
   5  * compiler.h
   6  *
   7  * Compiler definitions.
   8  *
   9  * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  10  *
  11  * Permission is hereby granted, free of charge, to any person obtaining a copy
  12  * of this software and associated documentation files (the "Software"), to deal
  13  * in the Software without restriction, including without limitation the rights
  14  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  15  * copies of the Software, and to permit persons to whom the Software is
  16  * furnished to do so, subject to the following conditions:
  17  *
  18  * The above copyright notice and this permission notice shall be included in
  19  * all copies or substantial portions of the Software.
  20  */
  21
  22 #include <stddef.h>     /* for offsetof */
  23
  24 #define caa_likely(x)   __builtin_expect(!!(x), 1)
  25 #define caa_unlikely(x) __builtin_expect(!!(x), 0)
  26
  27 #define cmm_barrier()   asm volatile("" : : : "memory")
  28
  29 /*
  30  * Instruct the compiler to perform only a single access to a variable
  31  * (prohibits merging and refetching). The compiler is also forbidden to reorder
  32  * successive instances of CMM_ACCESS_ONCE(), but only when the compiler is aware of
  33  * particular ordering. Compiler ordering can be ensured, for example, by
  34  * putting two CMM_ACCESS_ONCE() in separate C statements.
  35  *
  36  * This macro does absolutely -nothing- to prevent the CPU from reordering,
  37  * merging, or refetching absolutely anything at any time.  Its main intended
  38  * use is to mediate communication between process-level code and irq/NMI
  39  * handlers, all running on the same CPU.
  40  */
  41 #define CMM_ACCESS_ONCE(x)      (*(volatile typeof(x) *)&(x))
  42
  43 #ifndef caa_max
  44 #define caa_max(a,b) ((a)>(b)?(a):(b))
  45 #endif
  46
  47 #ifndef caa_min
  48 #define caa_min(a,b) ((a)<(b)?(a):(b))
  49 #endif
  50
  51 #if defined(__SIZEOF_LONG__)
  52 #define CAA_BITS_PER_LONG       (__SIZEOF_LONG__ * 8)
  53 #elif defined(_LP64)
  54 #define CAA_BITS_PER_LONG       64
  55 #else
  56 #define CAA_BITS_PER_LONG       32
  57 #endif
  58
  59 /*
  60  * caa_container_of - Get the address of an object containing a field.
  61  *
  62  * @ptr: pointer to the field.
  63  * @type: type of the object.
  64  * @member: name of the field within the object.
  65  */
  66 #define caa_container_of(ptr, type, member)                             \
  67         ({                                                              \
  68                 const typeof(((type *) NULL)->member) * __ptr = (ptr);  \
  69                 (type *)((char *)__ptr - offsetof(type, member));       \
  70         })
  71
  72 #define CAA_BUILD_BUG_ON_ZERO(cond) (sizeof(struct { int:-!!(cond); }))
  73 #define CAA_BUILD_BUG_ON(cond) ((void)BUILD_BUG_ON_ZERO(cond))
  74
  75 /*
  76  * __rcu is an annotation that documents RCU pointer accesses that need
  77  * to be protected by a read-side critical section. Eventually, a static
  78  * checker will be able to use this annotation to detect incorrect RCU
  79  * usage.
  80  */
  81 #define __rcu
  82
  83 #ifdef __cplusplus
  84 #define URCU_FORCE_CAST(type, arg)      (reinterpret_cast<type>(arg))
  85 #else
  86 #define URCU_FORCE_CAST(type, arg)      ((type) (arg))
  87 #endif
  88
  89 #define caa_is_signed_type(type)        (((type) (-1)) < 0)
  90
  91 #define caa_cast_long_keep_sign(v)      \
  92         (caa_is_signed_type(__typeof__(v)) ? (long) (v) : (unsigned long) (v))
  93
  94 #endif /* _URCU_COMPILER_H */