[userspace-rcu.git] / compiler.h

#ifndef _COMPILER_H
#define _COMPILER_H

/*
 * compiler.h
 *
 * Compiler definitions.
 *
 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
 *
 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
 * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
 *
 * Permission is hereby granted to use or copy this program
 * for any purpose,  provided the above notices are retained on all copies.
 * Permission to modify the code and to distribute modified code is granted,
 * provided the above notices are retained, and a notice that the code was
 * modified is included with the above copyright notice.
 */

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

#define	barrier()	asm volatile("" : : : "memory");

/*
 * Instruct the compiler to perform only a single access to a variable
 * (prohibits merging and refetching). The compiler is also forbidden to reorder
 * successive instances of ACCESS_ONCE(), but only when the compiler is aware of
 * particular ordering. Compiler ordering can be ensured, for example, by
 * putting two ACCESS_ONCE() in separate 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)

#if (__GNUC__ == 4)
#define __compiler_offsetof(a, b) __builtin_offsetof(a, b)
#endif

#ifdef __compiler_offsetof
#define offsetof(TYPE, MEMBER) __compiler_offsetof(TYPE, MEMBER)
#else
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
#endif

#endif /* _COMPILER_H */
Commit	Line	Data
	1	#ifndef _COMPILER_H
	2	#define _COMPILER_H
	3
	4	/*
	5	* compiler.h
	6	*
	7	* Compiler definitions.
	8	*
	9	* Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
	10	*
	11	* THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
	12	* OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
	13	*
	14	* Permission is hereby granted to use or copy this program
	15	* for any purpose, provided the above notices are retained on all copies.
	16	* Permission to modify the code and to distribute modified code is granted,
	17	* provided the above notices are retained, and a notice that the code was
	18	* modified is included with the above copyright notice.
	19	*/
	20
	21	#define likely(x) __builtin_expect(!!(x), 1)
	22	#define unlikely(x) __builtin_expect(!!(x), 0)
	23
	24	#define barrier() asm volatile("" : : : "memory");
	25
	26	/*
	27	* Instruct the compiler to perform only a single access to a variable
	28	* (prohibits merging and refetching). The compiler is also forbidden to reorder
	29	* successive instances of ACCESS_ONCE(), but only when the compiler is aware of
	30	* particular ordering. Compiler ordering can be ensured, for example, by
	31	* putting two ACCESS_ONCE() in separate C statements.
	32	*
	33	* This macro does absolutely -nothing- to prevent the CPU from reordering,
	34	* merging, or refetching absolutely anything at any time. Its main intended
	35	* use is to mediate communication between process-level code and irq/NMI
	36	* handlers, all running on the same CPU.
	37	*/
	38	#define ACCESS_ONCE(x) ((volatile typeof(x) )&x)
	39
	40	#if (__GNUC__ == 4)
	41	#define __compiler_offsetof(a, b) __builtin_offsetof(a, b)
	42	#endif
	43
	44	#ifdef __compiler_offsetof
	45	#define offsetof(TYPE, MEMBER) __compiler_offsetof(TYPE, MEMBER)
	46	#else
	47	#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
	48	#endif
	49
	50	#endif /* _COMPILER_H */