--- /dev/null
+/* mpn_dc_div_qr -- recursive divide-and-conquer division for arbitrary size
+ operands.
+
+ Contributed to the GNU project by Torbjörn Granlund.
+
+ THE FUNCTIONS IN THIS FILE ARE INTERNAL WITH A MUTABLE INTERFACE. IT IS
+ ONLY SAFE TO REACH THEM THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS
+ ALMOST GUARANTEED THAT THEY WILL CHANGE OR DISAPPEAR IN A FUTURE GMP
+ RELEASE.
+
+Copyright 2006, 2007 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 3 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. If not, see http://www.gnu.org/licenses/. */
+
+#include "gmp.h"
+#include "gmp-impl.h"
+
+
+mp_limb_t
+mpn_dc_div_qr_n (mp_ptr qp, mp_ptr np, mp_srcptr dp, mp_size_t n,
+ mp_srcptr dip, mp_ptr tp)
+{
+ mp_size_t lo, hi;
+ mp_limb_t cy, qh, ql;
+
+ lo = n >> 1; /* floor(n/2) */
+ hi = n - lo; /* ceil(n/2) */
+
+ if (BELOW_THRESHOLD (hi, DC_DIV_QR_THRESHOLD))
+ qh = mpn_sb_div_qr (qp + lo, np + 2 * lo, 2 * hi, dp + lo, hi, dip);
+ else
+ qh = mpn_dc_div_qr_n (qp + lo, np + 2 * lo, dp + lo, hi, dip, tp);
+
+ mpn_mul (tp, qp + lo, hi, dp, lo);
+
+ cy = mpn_sub_n (np + lo, np + lo, tp, n);
+ if (qh != 0)
+ cy += mpn_sub_n (np + n, np + n, dp, lo);
+
+ while (cy != 0)
+ {
+ qh -= mpn_sub_1 (qp + lo, qp + lo, hi, 1);
+ cy -= mpn_add_n (np + lo, np + lo, dp, n);
+ }
+
+ if (BELOW_THRESHOLD (lo, DC_DIV_QR_THRESHOLD))
+ ql = mpn_sb_div_qr (qp, np + hi, 2 * lo, dp + hi, lo, dip);
+ else
+ ql = mpn_dc_div_qr_n (qp, np + hi, dp + hi, lo, dip, tp);
+
+ mpn_mul (tp, dp, hi, qp, lo);
+
+ cy = mpn_sub_n (np, np, tp, n);
+ if (ql != 0)
+ cy += mpn_sub_n (np + lo, np + lo, dp, hi);
+
+ while (cy != 0)
+ {
+ mpn_sub_1 (qp, qp, lo, 1);
+ cy -= mpn_add_n (np, np, dp, n);
+ }
+
+ return qh;
+}
+
+mp_limb_t
+mpn_preinv_dc_div_qr (mp_ptr qp,
+ mp_ptr np, mp_size_t nn,
+ mp_srcptr dp, mp_size_t dn,
+ mp_srcptr dip)
+{
+ mp_size_t qn;
+ mp_limb_t qh, cy;
+ mp_ptr tp;
+ TMP_DECL;
+
+ TMP_MARK;
+
+ tp = TMP_SALLOC_LIMBS (dn);
+
+ qn = nn - dn;
+ qp += qn;
+ np += nn;
+ dp += dn;
+
+ if (qn > dn)
+ {
+ /* Reduce qn mod dn without division, optimizing small operations. */
+ do
+ qn -= dn;
+ while (qn > dn);
+
+ qp -= qn; /* point at low limb of next quotient block */
+ np -= qn; /* point in the middle of partial remainder */
+
+ /* Perform the typically smaller block first. */
+ if (BELOW_THRESHOLD (qn, DC_DIV_QR_THRESHOLD))
+ qh = mpn_sb_div_qr (qp, np - qn, 2 * qn, dp - qn, qn, dip);
+ else
+ qh = mpn_dc_div_qr_n (qp, np - qn, dp - qn, qn, dip, tp);
+
+ if (qn != dn)
+ {
+ if (qn > dn - qn)
+ mpn_mul (tp, qp, qn, dp - dn, dn - qn);
+ else
+ mpn_mul (tp, dp - dn, dn - qn, qp, qn);
+
+ cy = mpn_sub_n (np - dn, np - dn, tp, dn);
+ if (qh != 0)
+ cy += mpn_sub_n (np - dn + qn, np - dn + qn, dp - dn, dn - qn);
+
+ while (cy != 0)
+ {
+ qh -= mpn_sub_1 (qp, qp, qn, 1);
+ cy -= mpn_add_n (np - dn, np - dn, dp - dn, dn);
+ }
+ }
+
+ qn = nn - dn - qn;
+ do
+ {
+ qp -= dn;
+ np -= dn;
+ mpn_dc_div_qr_n (qp, np - dn, dp - dn, dn, dip, tp);
+ qn -= dn;
+ }
+ while (qn > 0);
+ }
+ else
+ {
+ if (qn == 0)
+ {
+ qh = mpn_cmp (np - dn, dp - dn, dn) >= 0;
+ if (qh)
+ mpn_sub_n (np - dn, np - dn, dp - dn, dn);
+ TMP_FREE;
+ return qh;
+ }
+
+ qp -= qn; /* point at low limb of next quotient block */
+ np -= qn; /* point in the middle of partial remainder */
+
+ if (BELOW_THRESHOLD (qn, DC_DIV_QR_THRESHOLD))
+ qh = mpn_sb_div_qr (qp, np - qn, 2 * qn, dp - qn, qn, dip);
+ else
+ qh = mpn_dc_div_qr_n (qp, np - qn, dp - qn, qn, dip, tp);
+
+ if (qn != dn)
+ {
+ if (qn > dn - qn)
+ mpn_mul (tp, qp, qn, dp - dn, dn - qn);
+ else
+ mpn_mul (tp, dp - dn, dn - qn, qp, qn);
+
+ cy = mpn_sub_n (np - dn, np - dn, tp, dn);
+ if (qh != 0)
+ cy += mpn_sub_n (np - dn + qn, np - dn + qn, dp - dn, dn - qn);
+
+ while (cy != 0)
+ {
+ qh -= mpn_sub_1 (qp, qp, qn, 1);
+ cy -= mpn_add_n (np - dn, np - dn, dp - dn, dn);
+ }
+ }
+ }
+
+ TMP_FREE;
+ return qh;
+}
+
+mp_limb_t
+mpn_dc_div_qr (mp_ptr qp, mp_ptr np, mp_size_t nn, mp_srcptr dp, mp_size_t dn)
+{
+ mp_limb_t cy;
+ mp_limb_t xp[2], dip[2];
+
+ ASSERT (dn >= 2);
+
+ cy = mpn_add_1 (xp, dp + dn - 2, 2, 1);
+ if (cy != 0)
+ dip[0] = dip[1] = 0;
+ else
+ {
+ mp_limb_t scratch[10]; /* FIXME */
+ mpn_invert (dip, xp, 2, scratch);
+ }
+
+ return mpn_preinv_dc_div_qr (qp, np, nn, dp, dn, dip);
+}
projects / msp430-gcc.git / blobdiff