LXR linux/include/linux/compiler-gcc.h

   1#ifndef __LINUX_COMPILER_H
   2#error "Please don't include <linux/compiler-gcc.h> directly, include <linux/compiler.h> instead."
   3#endif
   4
   5/*
   6 * Common definitions for all gcc versions go here.
   7 */
   8
   9
  10/* Optimization barrier */
  11/* The "volatile" is due to gcc bugs */
  12#define barrier() __asm__ __volatile__("": : :"memory")
  13
  14/*
  15 * This macro obfuscates arithmetic on a variable address so that gcc
  16 * shouldn't recognize the original var, and make assumptions about it.
  17 *
  18 * This is needed because the C standard makes it undefined to do
  19 * pointer arithmetic on "objects" outside their boundaries and the
  20 * gcc optimizers assume this is the case. In particular they
  21 * assume such arithmetic does not wrap.
  22 *
  23 * A miscompilation has been observed because of this on PPC.
  24 * To work around it we hide the relationship of the pointer and the object
  25 * using this macro.
  26 *
  27 * Versions of the ppc64 compiler before 4.1 had a bug where use of
  28 * RELOC_HIDE could trash r30. The bug can be worked around by changing
  29 * the inline assembly constraint from =g to =r, in this particular
  30 * case either is valid.
  31 */
  32#define RELOC_HIDE(ptr, off)                                    \
  33  ({ unsigned long __ptr;                                       \
  34    __asm__ ("" : "=r"(__ptr) : "0"(ptr));              \
  35    (typeof(ptr)) (__ptr + (off)); })
  36
  37#ifdef __CHECKER__
  38#define __must_be_array(arr) 0
  39#else
  40/* &a[0] degrades to a pointer: a different type from an array */
  41#define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
  42#endif
  43
  44/*
  45 * Force always-inline if the user requests it so via the .config,
  46 * or if gcc is too old:
  47 */
  48#if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \
  49    !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4)
  50# define inline         inline          __attribute__((always_inline))
  51# define __inline__     __inline__      __attribute__((always_inline))
  52# define __inline       __inline        __attribute__((always_inline))
  53#endif
  54
  55#define __deprecated                    __attribute__((deprecated))
  56#define __packed                        __attribute__((packed))
  57#define __weak                          __attribute__((weak))
  58
  59/*
  60 * it doesn't make sense on ARM (currently the only user of __naked) to trace
  61 * naked functions because then mcount is called without stack and frame pointer
  62 * being set up and there is no chance to restore the lr register to the value
  63 * before mcount was called.
  64 *
  65 * The asm() bodies of naked functions often depend on standard calling conventions,
  66 * therefore they must be noinline and noclone.  GCC 4.[56] currently fail to enforce
  67 * this, so we must do so ourselves.  See GCC PR44290.
  68 */
  69#define __naked                         __attribute__((naked)) noinline __noclone notrace
  70
  71#define __noreturn                      __attribute__((noreturn))
  72
  73/*
  74 * From the GCC manual:
  75 *
  76 * Many functions have no effects except the return value and their
  77 * return value depends only on the parameters and/or global
  78 * variables.  Such a function can be subject to common subexpression
  79 * elimination and loop optimization just as an arithmetic operator
  80 * would be.
  81 * [...]
  82 */
  83#define __pure                          __attribute__((pure))
  84#define __aligned(x)                    __attribute__((aligned(x)))
  85#define __printf(a,b)                   __attribute__((format(printf,a,b)))
  86#define  noinline                       __attribute__((noinline))
  87#define __attribute_const__             __attribute__((__const__))
  88#define __maybe_unused                  __attribute__((unused))
  89#define __always_unused                 __attribute__((unused))
  90
  91#define __gcc_header(x) #x
  92#define _gcc_header(x) __gcc_header(linux/compiler-gcc##x.h)
  93#define gcc_header(x) _gcc_header(x)
  94#include gcc_header(__GNUC__)
  95
  96#if !defined(__noclone)
  97#define __noclone       /* not needed */
  98#endif
  99
 100/*
 101 * A trick to suppress uninitialized variable warning without generating any
 102 * code
 103 */
 104#define uninitialized_var(x) x = x
 105
 106#define __always_inline         inline __attribute__((always_inline))
 107