include/urcu/compiler.h

   1 // SPDX-FileCopyrightText: 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   2 //
   3 // SPDX-License-Identifier: LGPL-2.1-or-later
   4
   5 #ifndef _URCU_COMPILER_H
   6 #define _URCU_COMPILER_H
   7
   8 /*
   9  * Compiler definitions.
  10  */
  11
  12 #include <stddef.h>     /* for offsetof */
  13
  14 #if defined __cplusplus
  15 # include <type_traits> /* for std::remove_cv */
  16 #endif
  17
  18 #include <urcu/config.h>
  19
  20 #define caa_likely(x)   __builtin_expect(!!(x), 1)
  21 #define caa_unlikely(x) __builtin_expect(!!(x), 0)
  22
  23 #ifdef CONFIG_RCU_USE_ATOMIC_BUILTINS
  24 #  define cmm_barrier() __atomic_signal_fence(__ATOMIC_SEQ_CST)
  25 #else
  26 #  define cmm_barrier() __asm__ __volatile__ ("" : : : "memory")
  27 #endif
  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         __extension__                                                   \
  68         ({                                                              \
  69                 const __typeof__(((type *) NULL)->member) * __ptr = (ptr); \
  70                 (type *)((char *)__ptr - offsetof(type, member));       \
  71         })
  72
  73 /*
  74  * caa_container_of_check_null - Get the address of an object containing a field.
  75  *
  76  * @ptr: pointer to the field.
  77  * @type: type of the object.
  78  * @member: name of the field within the object.
  79  *
  80  * Return the address of the object containing the field. Return NULL if
  81  * @ptr is NULL.
  82  */
  83 #define caa_container_of_check_null(ptr, type, member)                  \
  84         __extension__                                                   \
  85         ({                                                              \
  86                 const __typeof__(((type *) NULL)->member) * __ptr = (ptr); \
  87                 (__ptr) ? (type *)((char *)__ptr - offsetof(type, member)) : NULL; \
  88         })
  89
  90 #define CAA_BUILD_BUG_ON_ZERO(cond) (sizeof(struct { int:-!!(cond); }))
  91 #define CAA_BUILD_BUG_ON(cond) ((void)CAA_BUILD_BUG_ON_ZERO(cond))
  92
  93 /*
  94  * __rcu is an annotation that documents RCU pointer accesses that need
  95  * to be protected by a read-side critical section. Eventually, a static
  96  * checker will be able to use this annotation to detect incorrect RCU
  97  * usage.
  98  */
  99 #define __rcu
 100
 101 #ifdef __cplusplus
 102 #define URCU_FORCE_CAST(_type, arg)     (reinterpret_cast<std::remove_cv<_type>::type>(arg))
 103 #else
 104 #define URCU_FORCE_CAST(type, arg)      ((type) (arg))
 105 #endif
 106
 107 #define caa_is_signed_type(type)        ((type) -1 < (type) 0)
 108
 109 /*
 110  * Cast to unsigned long, sign-extending if @v is signed.
 111  * Note: casting to a larger type or to same type size keeps the sign of
 112  * the expression being cast (see C99 6.3.1.3).
 113  */
 114 #define caa_cast_long_keep_sign(v)      ((unsigned long) (v))
 115
 116 #if defined (__GNUC__) \
 117         && ((__GNUC__ == 4) && (__GNUC_MINOR__ >= 5)    \
 118                 || __GNUC__ >= 5)
 119 #define CDS_DEPRECATED(msg)     \
 120         __attribute__((deprecated(msg)))
 121 #else
 122 #define CDS_DEPRECATED(msg)     \
 123         __attribute__((deprecated))
 124 #endif
 125
 126 #define CAA_ARRAY_SIZE(x)       (sizeof(x) / sizeof((x)[0]))
 127
 128 /*
 129  * URCU_GCC_VERSION is used to blacklist specific GCC versions with known
 130  * bugs, clang also defines these macros to an equivalent GCC version it
 131  * claims to support, so exclude it.
 132  */
 133 #if defined(__GNUC__) && !defined(__clang__)
 134 # define URCU_GCC_VERSION       (__GNUC__ * 10000 \
 135                                 + __GNUC_MINOR__ * 100 \
 136                                 + __GNUC_PATCHLEVEL__)
 137 #endif
 138
 139 #endif /* _URCU_COMPILER_H */