compiler.h

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#ifndef __LINUX_COMPILER_H
#define __LINUX_COMPILER_H

#ifndef __ASSEMBLY__

#ifdef __CHECKER__
# define __user     __attribute__((noderef, address_space(1)))
# define __kernel   __attribute__((address_space(0)))
# define __safe     __attribute__((safe))
# define __force    __attribute__((force))
# define __nocast   __attribute__((nocast))
# define __iomem    __attribute__((noderef, address_space(2)))
# define __acquires(x)  __attribute__((context(x,0,1)))
# define __releases(x)  __attribute__((context(x,1,0)))
# define __acquire(x)   __context__(x,1)
# define __release(x)   __context__(x,-1)
# define __cond_lock(x,c)   ((c) ? ({ __acquire(x); 1; }) : 0)
# define __percpu   __attribute__((noderef, address_space(3)))
#ifdef CONFIG_SPARSE_RCU_POINTER
# define __rcu      __attribute__((noderef, address_space(4)))
#else
# define __rcu
#endif
extern void __chk_user_ptr(const volatile void __user *);
extern void __chk_io_ptr(const volatile void __iomem *);
#else
# define __user
# define __kernel
# define __safe
# define __force
# define __nocast
# define __iomem
# define __chk_user_ptr(x) (void)0
# define __chk_io_ptr(x) (void)0
# define __builtin_warning(x, y...) (1)
# define __acquires(x)
# define __releases(x)
# define __acquire(x) (void)0
# define __release(x) (void)0
# define __cond_lock(x,c) (c)
# define __percpu
# define __rcu
#endif

#ifdef __KERNEL__

#ifdef __GNUC__
#include <linux/compiler-gcc.h>
#endif

#define notrace __attribute__((no_instrument_function))

/* Intel compiler defines __GNUC__. So we will overwrite implementations
 * coming from above header files here
 */
#ifdef __INTEL_COMPILER
# include <linux/compiler-intel.h>
#endif

/*
 * Generic compiler-dependent macros required for kernel
 * build go below this comment. Actual compiler/compiler version
 * specific implementations come from the above header files
 */

struct ftrace_branch_data {
    const char *func;
    const char *file;
    unsigned line;
    union {
        struct {
            unsigned long correct;
            unsigned long incorrect;
        };
        struct {
            unsigned long miss;
            unsigned long hit;
        };
        unsigned long miss_hit[2];
    };
};

/*
 * Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code
 * to disable branch tracing on a per file basis.
 */
#if defined(CONFIG_TRACE_BRANCH_PROFILING) \
    && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__)
void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);

#define likely_notrace(x)   __builtin_expect(!!(x), 1)
#define unlikely_notrace(x) __builtin_expect(!!(x), 0)

#define __branch_check__(x, expect) ({                  \
            int ______r;                    \
            static struct ftrace_branch_data        \
                __attribute__((__aligned__(4)))     \
                __attribute__((section("_ftrace_annotated_branch"))) \
                ______f = {             \
                .func = __func__,           \
                .file = __FILE__,           \
                .line = __LINE__,           \
            };                      \
            ______r = likely_notrace(x);            \
            ftrace_likely_update(&______f, ______r, expect); \
            ______r;                    \
        })

/*
 * Using __builtin_constant_p(x) to ignore cases where the return
 * value is always the same.  This idea is taken from a similar patch
 * written by Daniel Walker.
 */
# ifndef likely
#  define likely(x) (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 1))
# endif
# ifndef unlikely
#  define unlikely(x)   (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 0))
# endif

#ifdef CONFIG_PROFILE_ALL_BRANCHES
/*
 * "Define 'is'", Bill Clinton
 * "Define 'if'", Steven Rostedt
 */
#define if(cond, ...) __trace_if( (cond , ## __VA_ARGS__) )
#define __trace_if(cond) \
    if (__builtin_constant_p((cond)) ? !!(cond) :           \
    ({                              \
        int ______r;                        \
        static struct ftrace_branch_data            \
            __attribute__((__aligned__(4)))         \
            __attribute__((section("_ftrace_branch")))  \
            ______f = {                 \
                .func = __func__,           \
                .file = __FILE__,           \
                .line = __LINE__,           \
            };                      \
        ______r = !!(cond);                 \
        ______f.miss_hit[______r]++;                    \
        ______r;                        \
    }))
#endif /* CONFIG_PROFILE_ALL_BRANCHES */

#else
# define likely(x)  __builtin_expect(!!(x), 1)
# define unlikely(x)    __builtin_expect(!!(x), 0)
#endif

/* Optimization barrier */
#ifndef barrier
# define barrier() __memory_barrier()
#endif

/* Unreachable code */
#ifndef unreachable
# define unreachable() do { } while (1)
#endif

#ifndef RELOC_HIDE
# define RELOC_HIDE(ptr, off)                   \
  ({ unsigned long __ptr;                   \
     __ptr = (unsigned long) (ptr);             \
    (typeof(ptr)) (__ptr + (off)); })
#endif

#endif /* __KERNEL__ */

#endif /* __ASSEMBLY__ */

#ifdef __KERNEL__
/*
 * Allow us to mark functions as 'deprecated' and have gcc emit a nice
 * warning for each use, in hopes of speeding the functions removal.
 * Usage is:
 *      int __deprecated foo(void)
 */
#ifndef __deprecated
# define __deprecated       /* unimplemented */
#endif

#ifdef MODULE
#define __deprecated_for_modules __deprecated
#else
#define __deprecated_for_modules
#endif

#ifndef __must_check
#define __must_check
#endif

#ifndef CONFIG_ENABLE_MUST_CHECK
#undef __must_check
#define __must_check
#endif
#ifndef CONFIG_ENABLE_WARN_DEPRECATED
#undef __deprecated
#undef __deprecated_for_modules
#define __deprecated
#define __deprecated_for_modules
#endif

/*
 * Allow us to avoid 'defined but not used' warnings on functions and data,
 * as well as force them to be emitted to the assembly file.
 *
 * As of gcc 3.4, static functions that are not marked with attribute((used))
 * may be elided from the assembly file.  As of gcc 3.4, static data not so
 * marked will not be elided, but this may change in a future gcc version.
 *
 * NOTE: Because distributions shipped with a backported unit-at-a-time
 * compiler in gcc 3.3, we must define __used to be __attribute__((used))
 * for gcc >=3.3 instead of 3.4.
 *
 * In prior versions of gcc, such functions and data would be emitted, but
 * would be warned about except with attribute((unused)).
 *
 * Mark functions that are referenced only in inline assembly as __used so
 * the code is emitted even though it appears to be unreferenced.
 */
#ifndef __used
# define __used         /* unimplemented */
#endif

#ifndef __maybe_unused
# define __maybe_unused     /* unimplemented */
#endif

#ifndef __always_unused
# define __always_unused    /* unimplemented */
#endif

#ifndef noinline
#define noinline
#endif

/*
 * Rather then using noinline to prevent stack consumption, use
 * noinline_for_stack instead.  For documentation reasons.
 */
#define noinline_for_stack noinline

#ifndef __always_inline
#define __always_inline inline
#endif

#endif /* __KERNEL__ */

/*
 * From the GCC manual:
 *
 * Many functions do not examine any values except their arguments,
 * and have no effects except the return value.  Basically this is
 * just slightly more strict class than the `pure' attribute above,
 * since function is not allowed to read global memory.
 *
 * Note that a function that has pointer arguments and examines the
 * data pointed to must _not_ be declared `const'.  Likewise, a
 * function that calls a non-`const' function usually must not be
 * `const'.  It does not make sense for a `const' function to return
 * `void'.
 */
#ifndef __attribute_const__
# define __attribute_const__    /* unimplemented */
#endif

/*
 * Tell gcc if a function is cold. The compiler will assume any path
 * directly leading to the call is unlikely.
 */

#ifndef __cold
#define __cold
#endif

/* Simple shorthand for a section definition */
#ifndef __section
# define __section(S) __attribute__ ((__section__(#S)))
#endif

#ifndef __visible
#define __visible
#endif

/* Are two types/vars the same type (ignoring qualifiers)? */
#ifndef __same_type
# define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
#endif

/* Compile time object size, -1 for unknown */
#ifndef __compiletime_object_size
# define __compiletime_object_size(obj) -1
#endif
#ifndef __compiletime_warning
# define __compiletime_warning(message)
#endif
#ifndef __compiletime_error
# define __compiletime_error(message)
#endif
#ifndef __linktime_error
# define __linktime_error(message)
#endif
/*
 * Prevent the compiler from merging or refetching accesses.  The compiler
 * is also forbidden from reordering successive instances of ACCESS_ONCE(),
 * but only when the compiler is aware of some particular ordering.  One way
 * to make the compiler aware of ordering is to put the two invocations of
 * ACCESS_ONCE() in different C statements.
 *
 * This macro does absolutely -nothing- to prevent the CPU from reordering,
 * merging, or refetching absolutely anything at any time.  Its main intended
 * use is to mediate communication between process-level code and irq/NMI
 * handlers, all running on the same CPU.
 */
#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))

#endif /* __LINUX_COMPILER_H */