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4c74403188
Change-Id: Iae65e95cfa0d92091b8b0a424ae36d88efa76aa9 Reviewed-on: https://review.haiku-os.org/c/buildtools/+/3020 Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>
101 lines
2.7 KiB
C
101 lines
2.7 KiB
C
/* mpn_sub_err1_n -- sub_n with one error term
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Contributed by David Harvey.
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THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE. IT IS ONLY
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SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS ALMOST
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GUARANTEED THAT IT'LL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.
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Copyright 2011 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of either:
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* the GNU Lesser General Public License as published by the Free
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Software Foundation; either version 3 of the License, or (at your
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option) any later version.
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or
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* the GNU General Public License as published by the Free Software
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Foundation; either version 2 of the License, or (at your option) any
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later version.
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or both in parallel, as here.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received copies of the GNU General Public License and the
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GNU Lesser General Public License along with the GNU MP Library. If not,
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see https://www.gnu.org/licenses/. */
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#include "gmp-impl.h"
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/*
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Computes:
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(1) {rp,n} := {up,n} - {vp,n} (just like mpn_sub_n) with incoming borrow cy,
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return value is borrow out.
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(2) Let c[i+1] = borrow from i-th limb subtraction (c[0] = cy).
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Computes c[1]*yp[n-1] + ... + c[n]*yp[0], stores two-limb result at ep.
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Requires n >= 1.
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None of the outputs may overlap each other or any of the inputs, except
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that {rp,n} may be equal to {up,n} or {vp,n}.
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*/
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mp_limb_t
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mpn_sub_err1_n (mp_ptr rp, mp_srcptr up, mp_srcptr vp,
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mp_ptr ep, mp_srcptr yp,
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mp_size_t n, mp_limb_t cy)
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{
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mp_limb_t el, eh, ul, vl, yl, zl, rl, sl, cy1, cy2;
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ASSERT (n >= 1);
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ASSERT (MPN_SAME_OR_SEPARATE_P (rp, up, n));
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ASSERT (MPN_SAME_OR_SEPARATE_P (rp, vp, n));
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ASSERT (! MPN_OVERLAP_P (rp, n, yp, n));
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ASSERT (! MPN_OVERLAP_P (ep, 2, up, n));
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ASSERT (! MPN_OVERLAP_P (ep, 2, vp, n));
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ASSERT (! MPN_OVERLAP_P (ep, 2, yp, n));
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ASSERT (! MPN_OVERLAP_P (ep, 2, rp, n));
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yp += n - 1;
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el = eh = 0;
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do
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{
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yl = *yp--;
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ul = *up++;
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vl = *vp++;
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/* ordinary sub_n */
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SUBC_LIMB (cy1, sl, ul, vl);
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SUBC_LIMB (cy2, rl, sl, cy);
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cy = cy1 | cy2;
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*rp++ = rl;
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/* update (eh:el) */
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zl = (-cy) & yl;
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el += zl;
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eh += el < zl;
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}
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while (--n);
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#if GMP_NAIL_BITS != 0
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eh = (eh << GMP_NAIL_BITS) + (el >> GMP_NUMB_BITS);
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el &= GMP_NUMB_MASK;
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#endif
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ep[0] = el;
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ep[1] = eh;
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return cy;
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}
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