cnt32_to_63.h

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/*
 *  Extend a 32-bit counter to 63 bits
 *
 *  Author: Nicolas Pitre
 *  Created:    December 3, 2006
 *  Copyright:  MontaVista Software, Inc.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation.
 */

#ifndef __LINUX_CNT32_TO_63_H__
#define __LINUX_CNT32_TO_63_H__

#include <linux/compiler.h>
#include <linux/types.h>
#include <asm/byteorder.h>

/* this is used only to give gcc a clue about good code generation */
union cnt32_to_63 {
    struct {
#if defined(__LITTLE_ENDIAN)
        u32 lo, hi;
#elif defined(__BIG_ENDIAN)
        u32 hi, lo;
#endif
    };
    u64 val;
};


#define cnt32_to_63(cnt_lo) \
({ \
    static u32 __m_cnt_hi; \
    union cnt32_to_63 __x; \
    __x.hi = __m_cnt_hi; \
    smp_rmb(); \
    __x.lo = (cnt_lo); \
    if (unlikely((s32)(__x.hi ^ __x.lo) < 0)) \
        __m_cnt_hi = __x.hi = (__x.hi ^ 0x80000000) + (__x.hi >> 31); \
    __x.val; \
})

#endif