mpir/mpn/generic/divrem_euclidean_qr_1.c

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/*
dnl Copyright 2009 Jason Moxham
dnl This file is part of the MPIR Library.
dnl The MPIR Library is free software; you can redistribute it and/or modify
dnl it under the terms of the GNU Lesser General Public License as published
dnl by the Free Software Foundation; either version 2.1 of the License, or (at
dnl your option) any later version.
dnl The MPIR Library is distributed in the hope that it will be useful, but
dnl WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
dnl or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
dnl License for more details.
dnl You should have received a copy of the GNU Lesser General Public License
dnl along with the MPIR Library; see the file COPYING.LIB. If not, write
dnl to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
dnl Boston, MA 02110-1301, USA.
*/
#include "mpir.h"
#include "gmp-impl.h"
#include "longlong.h"
// d is mormalized
#define udiv_inverse(i,d) do{mp_limb_t __X;udiv_qrnnd(i,__X,~(d),GMP_LIMB_MAX,d);}while(0)
// note double lenght inverse can easily be calculated from single length inverse
// d is normalize
#define udiv_double_inverse(ih,il,d) \
do{mp_limb_t __X;udiv_qrnnd(ih,__X,~(d),GMP_LIMB_MAX,d);udiv_qrnnd(il,__X,__X,GMP_LIMB_MAX,d);}while(0)
// set to 1=store or 0=not store
#define STORE_QUOTIENT 1
// set to 0=udiv 1=gmp-preinv 2-barrett
#define UDIV_METHOD 1
#if UDIV_NEEDS_NORMALIZATION==1 || UDIV_METHOD==1
#define NORMALIZE 1
#else
#define NORMALIZE 0
#endif
#if UDIV_METHOD==0
#define UDIV(q,r,h,l,d,i) udiv_qrnnd(q,r,h,l,d)
#endif
#if UDIV_METHOD==1
#define UDIV udiv_qrnnd_preinv
#endif
#if UDIV_METHOD==2
#define UDIV udiv_qrnnd_barrett
#endif
#if STORE_QUOTIENT
mp_limb_t mpn_divrem_euclidean_qr_1(mp_ptr qp,mp_srcptr xp,mp_size_t n,mp_limb_t d)
#else
mp_limb_t mpn_divrem_euclidean_r_1(mp_srcptr xp,mp_size_t n,mp_limb_t d)
#endif
{int j;mp_limb_t r=0,s=0,h,l,q,i;
ASSERT(n>0);ASSERT(d!=0);ASSERT_MPN(xp,n);ASSERT(MPN_SAME_OR_SEPARATE_P(qp,xp,n));
// for n=1 or n=2 probably faster to do a special case
#if NORMALIZE==1
count_leading_zeros(s,d);d=d<<s;
invert_limb(i,d);
#endif
for(j=n-1;j>=0;j--)
{l=xp[j]; // out dlimb is (h=r,l)
h=(l>>((GMP_LIMB_BITS-1-s))>>1);l=l<<s;// shift dlimb left by s
h=h+r; // carry in
UDIV(q,r,h,l,d,i); // carry out , carry-out to carry-in is the critical latency bottleneck
#if STORE_QUOTIENT
qp[j]=q;
#endif
}
ASSERT((r<<(GMP_LIMB_BITS-1-s)<<1)==0);// ie bottom s bits of r are zero
r>>=s;
return r;} // so (xp,n) = (qp,n)*d +r and 0 <= r < d
/*
in hensel-div we use shiftout which means we can use mmx shifting and dont need to always use it
in euclid-div shiftout needs a final div for the remainder
*/