[urcu.git] / urcu / compiler.h

#ifndef _URCU_COMPILER_H
#define _URCU_COMPILER_H

/*
 * compiler.h
 *
 * Compiler definitions.
 *
 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * 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.
 */

#include <stddef.h>	/* for offsetof */

#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))

#ifndef max
#define max(a,b) ((a)>(b)?(a):(b))
#endif

#ifndef min
#define min(a,b) ((a)<(b)?(a):(b))
#endif

#if defined(__SIZEOF_LONG__)
#define BITS_PER_LONG	(__SIZEOF_LONG__ * 8)
#elif defined(_LP64)
#define BITS_PER_LONG	64
#else
#define BITS_PER_LONG	32
#endif

#endif /* _URCU_COMPILER_H */
Commit	Line	Data
ec4e58a3 MD	1	#ifndef _URCU_COMPILER_H
ec4e58a3 MD	2	#define _URCU_COMPILER_H
af02d47e MD	3
	4	/*
	5	* compiler.h
	6	*
	7	* Compiler definitions.
	8	*
6982d6d7	9	* Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
af02d47e	10	*
329045f0 MD	11	* THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
329045f0 MD	12	* OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
af02d47e	13	*
329045f0 MD	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.
af02d47e MD	19	*/
af02d47e MD	20
49d7d158 MD	21	#include <stddef.h> /* for offsetof */
49d7d158 MD	22
329045f0 MD	23	#define likely(x) __builtin_expect(!!(x), 1)
329045f0 MD	24	#define unlikely(x) __builtin_expect(!!(x), 0)
2dc5fa0f	25
f540a0fd	26	#define barrier() asm volatile("" : : : "memory")
2dc5fa0f	27
af02d47e MD	28	/*
	29	* Instruct the compiler to perform only a single access to a variable
	30	* (prohibits merging and refetching). The compiler is also forbidden to reorder
	31	* successive instances of ACCESS_ONCE(), but only when the compiler is aware of
	32	* particular ordering. Compiler ordering can be ensured, for example, by
	33	* putting two ACCESS_ONCE() in separate C statements.
	34	*
	35	* This macro does absolutely -nothing- to prevent the CPU from reordering,
	36	* merging, or refetching absolutely anything at any time. Its main intended
	37	* use is to mediate communication between process-level code and irq/NMI
	38	* handlers, all running on the same CPU.
	39	*/
56b14eae	40	#define ACCESS_ONCE(x) ((volatile typeof(x) )&(x))
af02d47e	41
fdee2e6d MD	42	#ifndef max
	43	#define max(a,b) ((a)>(b)?(a):(b))
	44	#endif
	45
	46	#ifndef min
	47	#define min(a,b) ((a)<(b)?(a):(b))
	48	#endif
	49
1b27a772 PB	50	#if defined(__SIZEOF_LONG__)
	51	#define BITS_PER_LONG (__SIZEOF_LONG__ * 8)
	52	#elif defined(_LP64)
	53	#define BITS_PER_LONG 64
	54	#else
	55	#define BITS_PER_LONG 32
	56	#endif
	57
ec4e58a3	58	#endif /* _URCU_COMPILER_H */