libsum/common/sum-att.c

	sum-att.c revision 34f9b3eef6fdadbda0a846aa4d68691ac40eace5
/***********************************************************************
*                                                                      *
*               This software is part of the ast package               *
*          Copyright (c) 1996-2009 AT&T Intellectual Property          *
*                      and is licensed under the                       *
*                  Common Public License, Version 1.0                  *
*                    by AT&T Intellectual Property                     *
*                                                                      *
*                A copy of the License is available at                 *
*            http://www.opensource.org/licenses/cpl1.0.txt             *
*         (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9)         *
*                                                                      *
*              Information and Software Systems Research               *
*                            AT&T Research                             *
*                           Florham Park NJ                            *
*                                                                      *
*                 Glenn Fowler <gsf@research.att.com>                  *
*                                                                      *
***********************************************************************/
#pragma prototyped

/*
 * att
 */

#define att_description \
    "The system 5 release 4 checksum. This is the default for \bsum\b \
    when \bgetconf UNIVERSE\b is \batt\b. This is the only true sum; \
    all of the other methods are order dependent."
#define att_options 0
#define att_match   "att|sys5|s5|default"
#define att_open    long_open
#define att_init    long_init
#define att_print   long_print
#define att_data    long_data
#define att_scale   512

#if defined(__SUNPRO_C) || defined(__GNUC__)

#if defined(__SUNPRO_C)
#    include <sun_prefetch.h>
#    define sum_prefetch(addr) sun_prefetch_read_many((void *)(addr))
#elif defined(__GNUC__)
#    define sum_prefetch(addr) __builtin_prefetch((addr), 0, 3)
#else
#    error Unknown compiler
#endif

#define CBLOCK_SIZE (64)
#pragma unroll(16)

/* Inmos transputer would love this algorithm */
static int
att_block(register Sum_t* p, const void* s, size_t n)
{
    register uint32_t   c = ((Integral_t*)p)->sum;
    register const unsigned char*   b = (const unsigned char*)s;
    register const unsigned char*   e = b + n;
    register uint32_t s0, s1, s2, s3, s4, s5, s6, s7;
    register unsigned int i;

    s0=s1=s2=s3=s4=s5=s6=s7=0U;

    sum_prefetch((void *)b);

    while (n > CBLOCK_SIZE)
    {
        sum_prefetch((b+CBLOCK_SIZE));

        /* Compiler will unroll for() loops per #pragma unroll */
        for (i=0 ; i < (CBLOCK_SIZE/8) ; i++)
        {
            /*
             * use s0-s7 to decouple calculations (this improves pipelining)
             * because each operation is completely independent from it's
             * siblings
             */
            s0+=b[0];
            s1+=b[1];
            s2+=b[2];
            s3+=b[3];
            s4+=b[4];
            s5+=b[5];
            s6+=b[6];
            s7+=b[7];

            b+=8;
            n-=8;
        }
    }

    c+=s0+s1+s2+s3+s4+s5+s6+s7;

    while (b < e)
        c += *b++;
    ((Integral_t*)p)->sum = c;
    return 0;
}

#else
static int
att_block(register Sum_t* p, const void* s, size_t n)
{
    register uint32_t   c = ((Integral_t*)p)->sum;
    register unsigned char* b = (unsigned char*)s;
    register unsigned char* e = b + n;

    while (b < e)
        c += *b++;
    ((Integral_t*)p)->sum = c;
    return 0;
}
#endif /* defined(__SUNPRO_C) || defined(__GNUC__) */

static int
att_done(Sum_t* p)
{
    register uint32_t   c = ((Integral_t*)p)->sum;

    c = (c & 0xffff) + ((c >> 16) & 0xffff);
    c = (c & 0xffff) + (c >> 16);
    ((Integral_t*)p)->sum = c & 0xffff;
    return short_done(p);
}