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/* mpn_sec_div_qr, mpn_sec_div_r -- Compute Q = floor(U / V), U = U mod V.
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Side-channel silent under the assumption that the used instructions are
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side-channel silent.
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Contributed to the GNU project by Torbjörn Granlund.
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Copyright 2011-2014 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.h"
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#include "gmp-impl.h"
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#include "longlong.h"
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#if OPERATION_sec_div_qr
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#define FNAME mpn_sec_div_qr
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#define FNAME_itch mpn_sec_div_qr_itch
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#define Q(q) q,
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#define RETTYPE mp_limb_t
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#endif
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#if OPERATION_sec_div_r
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#define FNAME mpn_sec_div_r
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#define FNAME_itch mpn_sec_div_r_itch
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#define Q(q)
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#define RETTYPE void
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#endif
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mp_size_t
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FNAME_itch (mp_size_t nn, mp_size_t dn)
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{
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#if OPERATION_sec_div_qr
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/* Needs (nn + dn + 1) + mpn_sec_pi1_div_qr's needs of (2nn' - dn + 1) for a
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total of 3nn + 4 limbs at tp. Note that mpn_sec_pi1_div_qr's nn is one
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greater than ours, therefore +4 and not just +2. */
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return 3 * nn + 4;
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#endif
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#if OPERATION_sec_div_r
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/* Needs (nn + dn + 1) + mpn_sec_pi1_div_r's needs of (dn + 1) for a total of
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nn + 2dn + 2 limbs at tp. */
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return nn + 2 * dn + 2;
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#endif
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}
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RETTYPE
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FNAME (Q(mp_ptr qp)
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mp_ptr np, mp_size_t nn,
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mp_srcptr dp, mp_size_t dn,
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mp_ptr tp)
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{
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mp_limb_t d1, d0;
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unsigned int cnt;
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gmp_pi1_t dinv;
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mp_limb_t inv32;
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ASSERT (dn >= 1);
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ASSERT (nn >= dn);
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ASSERT (dp[dn - 1] != 0);
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d1 = dp[dn - 1];
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count_leading_zeros (cnt, d1);
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if (cnt != 0)
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{
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mp_limb_t qh, cy;
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mp_ptr np2, dp2;
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dp2 = tp; /* dn limbs */
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mpn_lshift (dp2, dp, dn, cnt);
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np2 = tp + dn; /* (nn + 1) limbs */
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cy = mpn_lshift (np2, np, nn, cnt);
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np2[nn++] = cy;
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d0 = dp2[dn - 1];
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d0 += (~d0 != 0);
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invert_limb (inv32, d0);
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/* We add nn + dn to tp here, not nn + 1 + dn, as expected. This is
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since nn here will have been incremented. */
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#if OPERATION_sec_div_qr
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qh = mpn_sec_pi1_div_qr (np2 + dn, np2, nn, dp2, dn, inv32, tp + nn + dn);
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ASSERT (qh == 0); /* FIXME: this indicates inefficiency! */
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MPN_COPY (qp, np2 + dn, nn - dn - 1);
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qh = np2[nn - 1];
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#else
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mpn_sec_pi1_div_r (np2, nn, dp2, dn, inv32, tp + nn + dn);
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#endif
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mpn_rshift (np, np2, dn, cnt);
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#if OPERATION_sec_div_qr
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return qh;
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#endif
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}
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else
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{
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/* FIXME: Consider copying np => np2 here, adding a 0-limb at the top.
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That would simplify the underlying pi1 function, since then it could
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assume nn > dn. */
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d0 = dp[dn - 1];
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d0 += (~d0 != 0);
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invert_limb (inv32, d0);
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#if OPERATION_sec_div_qr
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return mpn_sec_pi1_div_qr (qp, np, nn, dp, dn, inv32, tp);
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#else
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mpn_sec_pi1_div_r (np, nn, dp, dn, inv32, tp);
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#endif
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}
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}
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