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/*
* include/common/compiler.h
* This files contains some compiler-specific settings.
*
* Copyright (C) 2000-2009 Willy Tarreau - w@1wt.eu
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation, version 2.1
* exclusively.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef _COMMON_COMPILER_H
#define _COMMON_COMPILER_H
/*
* Gcc before 3.0 needs [0] to declare a variable-size array
*/
#ifndef VAR_ARRAY
#if __GNUC__ < 3
#define VAR_ARRAY 0
#else
#define VAR_ARRAY
#endif
#endif
/* Support passing function parameters in registers. For this, the
* CONFIG_REGPARM macro has to be set to the maximal number of registers
* allowed. Some functions have intentionally received a regparm lower than
* their parameter count, it is in order to avoid register clobbering where
* they are called.
*/
#ifndef REGPRM1
#if CONFIG_REGPARM >= 1 && __GNUC__ >= 3
#define REGPRM1 __attribute__((regparm(1)))
#else
#define REGPRM1
#endif
#endif
#ifndef REGPRM2
#if CONFIG_REGPARM >= 2 && __GNUC__ >= 3
#define REGPRM2 __attribute__((regparm(2)))
#else
#define REGPRM2 REGPRM1
#endif
#endif
#ifndef REGPRM3
#if CONFIG_REGPARM >= 3 && __GNUC__ >= 3
#define REGPRM3 __attribute__((regparm(3)))
#else
#define REGPRM3 REGPRM2
#endif
#endif
/* By default, gcc does not inline large chunks of code, but we want it to
* respect our choices.
*/
#if !defined(forceinline)
#if __GNUC__ < 3
#define forceinline inline
#else
#define forceinline inline __attribute__((always_inline))
#endif
#endif
/* silence the "unused" warnings without having to place painful #ifdefs.
* For use with variables or functions.
*/
#define __maybe_unused __attribute__((unused))
/* This allows gcc to know that some locations are never reached, for example
* after a longjmp() in the Lua code, hence that some errors caught by such
* methods cannot propagate further. This is important with gcc versions 6 and
* above which can more aggressively detect null dereferences. The builtin
* below was introduced in gcc 4.5, and before it we didn't care.
*/
#if __GNUC__ >= 5 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)
#define my_unreachable() __builtin_unreachable()
#else
#define my_unreachable()
#endif
/*
* Gcc >= 3 provides the ability for the programme to give hints to the
* compiler about what branch of an if is most likely to be taken. This
* helps the compiler produce the most compact critical paths, which is
* generally better for the cache and to reduce the number of jumps.
*/
#if !defined(likely)
#if __GNUC__ < 3
#define __builtin_expect(x,y) (x)
#define likely(x) (x)
#define unlikely(x) (x)
#elif __GNUC__ < 4 || __GNUC__ >= 5
/* gcc 3.x and 5.x do the best job at this */
#define likely(x) (__builtin_expect((x) != 0, 1))
#define unlikely(x) (__builtin_expect((x) != 0, 0))
#else
/* GCC 4.x is stupid, it performs the comparison then compares it to 1,
* so we cheat in a dirty way to prevent it from doing this. This will
* only work with ints and booleans though.
*/
#define likely(x) (x)
#define unlikely(x) (__builtin_expect((unsigned long)(x), 0))
#endif
#endif
#endif /* _COMMON_COMPILER_H */
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