linux/include/linux/compiler.h
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   1#ifndef __LINUX_COMPILER_H
   2#define __LINUX_COMPILER_H
   3
   4#ifndef __ASSEMBLY__
   5
   6#ifdef __CHECKER__
   7# define __user         __attribute__((noderef, address_space(1)))
   8# define __kernel       __attribute__((address_space(0)))
   9# define __safe         __attribute__((safe))
  10# define __force        __attribute__((force))
  11# define __nocast       __attribute__((nocast))
  12# define __iomem        __attribute__((noderef, address_space(2)))
  13# define __acquires(x)  __attribute__((context(x,0,1)))
  14# define __releases(x)  __attribute__((context(x,1,0)))
  15# define __acquire(x)   __context__(x,1)
  16# define __release(x)   __context__(x,-1)
  17# define __cond_lock(x,c)       ((c) ? ({ __acquire(x); 1; }) : 0)
  18# define __percpu       __attribute__((noderef, address_space(3)))
  19#ifdef CONFIG_SPARSE_RCU_POINTER
  20# define __rcu          __attribute__((noderef, address_space(4)))
  21#else
  22# define __rcu
  23#endif
  24extern void __chk_user_ptr(const volatile void __user *);
  25extern void __chk_io_ptr(const volatile void __iomem *);
  26#else
  27# define __user
  28# define __kernel
  29# define __safe
  30# define __force
  31# define __nocast
  32# define __iomem
  33# define __chk_user_ptr(x) (void)0
  34# define __chk_io_ptr(x) (void)0
  35# define __builtin_warning(x, y...) (1)
  36# define __acquires(x)
  37# define __releases(x)
  38# define __acquire(x) (void)0
  39# define __release(x) (void)0
  40# define __cond_lock(x,c) (c)
  41# define __percpu
  42# define __rcu
  43#endif
  44
  45#ifdef __KERNEL__
  46
  47#ifdef __GNUC__
  48#include <linux/compiler-gcc.h>
  49#endif
  50
  51#define notrace __attribute__((no_instrument_function))
  52
  53/* Intel compiler defines __GNUC__. So we will overwrite implementations
  54 * coming from above header files here
  55 */
  56#ifdef __INTEL_COMPILER
  57# include <linux/compiler-intel.h>
  58#endif
  59
  60/*
  61 * Generic compiler-dependent macros required for kernel
  62 * build go below this comment. Actual compiler/compiler version
  63 * specific implementations come from the above header files
  64 */
  65
  66struct ftrace_branch_data {
  67        const char *func;
  68        const char *file;
  69        unsigned line;
  70        union {
  71                struct {
  72                        unsigned long correct;
  73                        unsigned long incorrect;
  74                };
  75                struct {
  76                        unsigned long miss;
  77                        unsigned long hit;
  78                };
  79                unsigned long miss_hit[2];
  80        };
  81};
  82
  83/*
  84 * Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code
  85 * to disable branch tracing on a per file basis.
  86 */
  87#if defined(CONFIG_TRACE_BRANCH_PROFILING) \
  88    && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__)
  89void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
  90
  91#define likely_notrace(x)       __builtin_expect(!!(x), 1)
  92#define unlikely_notrace(x)     __builtin_expect(!!(x), 0)
  93
  94#define __branch_check__(x, expect) ({                                  \
  95                        int ______r;                                    \
  96                        static struct ftrace_branch_data                \
  97                                __attribute__((__aligned__(4)))         \
  98                                __attribute__((section("_ftrace_annotated_branch"))) \
  99                                ______f = {                             \
 100                                .func = __func__,                       \
 101                                .file = __FILE__,                       \
 102                                .line = __LINE__,                       \
 103                        };                                              \
 104                        ______r = likely_notrace(x);                    \
 105                        ftrace_likely_update(&______f, ______r, expect); \
 106                        ______r;                                        \
 107                })
 108
 109/*
 110 * Using __builtin_constant_p(x) to ignore cases where the return
 111 * value is always the same.  This idea is taken from a similar patch
 112 * written by Daniel Walker.
 113 */
 114# ifndef likely
 115#  define likely(x)     (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 1))
 116# endif
 117# ifndef unlikely
 118#  define unlikely(x)   (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 0))
 119# endif
 120
 121#ifdef CONFIG_PROFILE_ALL_BRANCHES
 122/*
 123 * "Define 'is'", Bill Clinton
 124 * "Define 'if'", Steven Rostedt
 125 */
 126#define if(cond, ...) __trace_if( (cond , ## __VA_ARGS__) )
 127#define __trace_if(cond) \
 128        if (__builtin_constant_p((cond)) ? !!(cond) :                   \
 129        ({                                                              \
 130                int ______r;                                            \
 131                static struct ftrace_branch_data                        \
 132                        __attribute__((__aligned__(4)))                 \
 133                        __attribute__((section("_ftrace_branch")))      \
 134                        ______f = {                                     \
 135                                .func = __func__,                       \
 136                                .file = __FILE__,                       \
 137                                .line = __LINE__,                       \
 138                        };                                              \
 139                ______r = !!(cond);                                     \
 140                ______f.miss_hit[______r]++;                                    \
 141                ______r;                                                \
 142        }))
 143#endif /* CONFIG_PROFILE_ALL_BRANCHES */
 144
 145#else
 146# define likely(x)      __builtin_expect(!!(x), 1)
 147# define unlikely(x)    __builtin_expect(!!(x), 0)
 148#endif
 149
 150/* Optimization barrier */
 151#ifndef barrier
 152# define barrier() __memory_barrier()
 153#endif
 154
 155/* Unreachable code */
 156#ifndef unreachable
 157# define unreachable() do { } while (1)
 158#endif
 159
 160#ifndef RELOC_HIDE
 161# define RELOC_HIDE(ptr, off)                                   \
 162  ({ unsigned long __ptr;                                       \
 163     __ptr = (unsigned long) (ptr);                             \
 164    (typeof(ptr)) (__ptr + (off)); })
 165#endif
 166
 167#endif /* __KERNEL__ */
 168
 169#endif /* __ASSEMBLY__ */
 170
 171#ifdef __KERNEL__
 172/*
 173 * Allow us to mark functions as 'deprecated' and have gcc emit a nice
 174 * warning for each use, in hopes of speeding the functions removal.
 175 * Usage is:
 176 *              int __deprecated foo(void)
 177 */
 178#ifndef __deprecated
 179# define __deprecated           /* unimplemented */
 180#endif
 181
 182#ifdef MODULE
 183#define __deprecated_for_modules __deprecated
 184#else
 185#define __deprecated_for_modules
 186#endif
 187
 188#ifndef __must_check
 189#define __must_check
 190#endif
 191
 192#ifndef CONFIG_ENABLE_MUST_CHECK
 193#undef __must_check
 194#define __must_check
 195#endif
 196#ifndef CONFIG_ENABLE_WARN_DEPRECATED
 197#undef __deprecated
 198#undef __deprecated_for_modules
 199#define __deprecated
 200#define __deprecated_for_modules
 201#endif
 202
 203/*
 204 * Allow us to avoid 'defined but not used' warnings on functions and data,
 205 * as well as force them to be emitted to the assembly file.
 206 *
 207 * As of gcc 3.4, static functions that are not marked with attribute((used))
 208 * may be elided from the assembly file.  As of gcc 3.4, static data not so
 209 * marked will not be elided, but this may change in a future gcc version.
 210 *
 211 * NOTE: Because distributions shipped with a backported unit-at-a-time
 212 * compiler in gcc 3.3, we must define __used to be __attribute__((used))
 213 * for gcc >=3.3 instead of 3.4.
 214 *
 215 * In prior versions of gcc, such functions and data would be emitted, but
 216 * would be warned about except with attribute((unused)).
 217 *
 218 * Mark functions that are referenced only in inline assembly as __used so
 219 * the code is emitted even though it appears to be unreferenced.
 220 */
 221#ifndef __used
 222# define __used                 /* unimplemented */
 223#endif
 224
 225#ifndef __maybe_unused
 226# define __maybe_unused         /* unimplemented */
 227#endif
 228
 229#ifndef __always_unused
 230# define __always_unused        /* unimplemented */
 231#endif
 232
 233#ifndef noinline
 234#define noinline
 235#endif
 236
 237/*
 238 * Rather then using noinline to prevent stack consumption, use
 239 * noinline_for_stack instead.  For documentation reasons.
 240 */
 241#define noinline_for_stack noinline
 242
 243#ifndef __always_inline
 244#define __always_inline inline
 245#endif
 246
 247#endif /* __KERNEL__ */
 248
 249/*
 250 * From the GCC manual:
 251 *
 252 * Many functions do not examine any values except their arguments,
 253 * and have no effects except the return value.  Basically this is
 254 * just slightly more strict class than the `pure' attribute above,
 255 * since function is not allowed to read global memory.
 256 *
 257 * Note that a function that has pointer arguments and examines the
 258 * data pointed to must _not_ be declared `const'.  Likewise, a
 259 * function that calls a non-`const' function usually must not be
 260 * `const'.  It does not make sense for a `const' function to return
 261 * `void'.
 262 */
 263#ifndef __attribute_const__
 264# define __attribute_const__    /* unimplemented */
 265#endif
 266
 267/*
 268 * Tell gcc if a function is cold. The compiler will assume any path
 269 * directly leading to the call is unlikely.
 270 */
 271
 272#ifndef __cold
 273#define __cold
 274#endif
 275
 276/* Simple shorthand for a section definition */
 277#ifndef __section
 278# define __section(S) __attribute__ ((__section__(#S)))
 279#endif
 280
 281#ifndef __visible
 282#define __visible
 283#endif
 284
 285/* Are two types/vars the same type (ignoring qualifiers)? */
 286#ifndef __same_type
 287# define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
 288#endif
 289
 290/* Compile time object size, -1 for unknown */
 291#ifndef __compiletime_object_size
 292# define __compiletime_object_size(obj) -1
 293#endif
 294#ifndef __compiletime_warning
 295# define __compiletime_warning(message)
 296#endif
 297#ifndef __compiletime_error
 298# define __compiletime_error(message)
 299#endif
 300#ifndef __linktime_error
 301# define __linktime_error(message)
 302#endif
 303/*
 304 * Prevent the compiler from merging or refetching accesses.  The compiler
 305 * is also forbidden from reordering successive instances of ACCESS_ONCE(),
 306 * but only when the compiler is aware of some particular ordering.  One way
 307 * to make the compiler aware of ordering is to put the two invocations of
 308 * ACCESS_ONCE() in different C statements.
 309 *
 310 * This macro does absolutely -nothing- to prevent the CPU from reordering,
 311 * merging, or refetching absolutely anything at any time.  Its main intended
 312 * use is to mediate communication between process-level code and irq/NMI
 313 * handlers, all running on the same CPU.
 314 */
 315#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
 316
 317#endif /* __LINUX_COMPILER_H */
 318
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