/* mpn_hamdist --

Copyright (C) 1994, 1996, 2000 Free Software Foundation, Inc.

This file is part of the GNU MP Library.

The GNU MP 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; either version 2.1 of the License, or (at your
option) any later version.

The GNU MP 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 the GNU MP Library; see the file COPYING.LIB.  If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */

#include "gmp.h"
#include "gmp-impl.h"

#if defined __GNUC__
/* No processor claiming to be SPARC v9 compliant seem to
   implement the POPC instruction.  Disable pattern for now.  */
#if 0 && defined __sparc_v9__ && BITS_PER_MP_LIMB == 64
#define popc_limb(a) \
  ({									\
    DItype __res;							\
    asm ("popc %1,%0" : "=r" (__res) : "rI" (a));			\
    __res;								\
  })
#endif
#endif

#ifndef popc_limb

/* Cool population count of a mp_limb_t.
   You have to figure out how this works, I won't tell you!  */

static inline unsigned int
#if __STDC__
popc_limb (mp_limb_t x)
#else
popc_limb (x)
     mp_limb_t x;
#endif
{
#if BITS_PER_MP_LIMB == 64
  /* We have to go into some trouble to define these constants.
     (For mp_limb_t being `long long'.)  */
  mp_limb_t cnst;
  cnst = 0xaaaaaaaaL | ((mp_limb_t) 0xaaaaaaaaL << BITS_PER_MP_LIMB/2);
  x -= (x & cnst) >> 1;
  cnst = 0x33333333L | ((mp_limb_t) 0x33333333L << BITS_PER_MP_LIMB/2);
  x = ((x & ~cnst) >> 2) + (x & cnst);
  cnst = 0x0f0f0f0fL | ((mp_limb_t) 0x0f0f0f0fL << BITS_PER_MP_LIMB/2);
  x = ((x >> 4) + x) & cnst;
  x = ((x >> 8) + x);
  x = ((x >> 16) + x);
  x = ((x >> 32) + x) & 0xff;
#endif
#if BITS_PER_MP_LIMB == 32
  x -= (x & 0xaaaaaaaa) >> 1;
  x = ((x >> 2) & 0x33333333L) + (x & 0x33333333L);
  x = ((x >> 4) + x) & 0x0f0f0f0fL;
  x = ((x >> 8) + x);
  x = ((x >> 16) + x) & 0xff;
#endif
  return x;
}
#endif

unsigned long int
#if __STDC__
mpn_hamdist (mp_srcptr up, mp_srcptr vp, mp_size_t size)
#else
mpn_hamdist (up, vp, size)
     register mp_srcptr up;
     register mp_srcptr vp;
     register mp_size_t size;
#endif
{
  unsigned long int hamdist;
  mp_size_t i;

  hamdist = 0;
  for (i = 0; i < size; i++)
    hamdist += popc_limb (up[i] ^ vp[i]);

  return hamdist;
}