compiler.h

xen虚拟机源代码安装包

#ifndef __LINUX_COMPILER_H
#define __LINUX_COMPILER_H

#if !defined(__GNUC__) || (__GNUC__ < 3)
#error Sorry, your compiler is too old/not recognized.
#endif

#define barrier()     __asm__ __volatile__("": : :"memory")

#define likely(x)     __builtin_expect((x),1)
#define unlikely(x)   __builtin_expect((x),0)

#define inline        __inline__
#define always_inline __inline__ __attribute__ ((always_inline))
#define noinline      __attribute__((noinline))

#define __attribute_pure__  __attribute__((pure))
#define __attribute_const__ __attribute__((__const__))

#if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 3)
#define __attribute_used__ __attribute__((__used__))
#else
#define __attribute_used__ __attribute__((__unused__))
#endif

#if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)
#define __must_check __attribute__((warn_unused_result))
#else
#define __must_check
#endif

#if __GNUC__ > 3
#define offsetof(a,b) __builtin_offsetof(a,b)
#else
#define offsetof(a,b) ((unsigned long)&(((a *)0)->b))
#endif

#ifdef GCC_HAS_VISIBILITY_ATTRIBUTE
/* Results in more efficient PIC code (no indirections through GOT or PLT). */
#pragma GCC visibility push(hidden)
#endif

/* This macro obfuscates arithmetic on a variable address so that gcc
   shouldn't recognize the original var, and make assumptions about it */
/*
 * Versions of the ppc64 compiler before 4.1 had a bug where use of
 * RELOC_HIDE could trash r30. The bug can be worked around by changing
 * the inline assembly constraint from =g to =r, in this particular
 * case either is valid.
 */
#define RELOC_HIDE(ptr, off)                    \
  ({ unsigned long __ptr;                       \
    __asm__ ("" : "=r"(__ptr) : "0"(ptr));      \
    (typeof(ptr)) (__ptr + (off)); })

/*
 * A trick to suppress uninitialized variable warning without generating any
 * code
 */
#define uninitialized_var(x) x = x

#endif /* __LINUX_COMPILER_H */