--- /dev/null
+/* mpn_preinv_divrem_1 -- mpn by limb division with pre-inverted divisor.
+
+ THE FUNCTIONS IN THIS FILE ARE FOR INTERNAL USE ONLY. THEY'RE ALMOST
+ CERTAIN TO BE SUBJECT TO INCOMPATIBLE CHANGES OR DISAPPEAR COMPLETELY IN
+ FUTURE GNU MP RELEASES.
+
+Copyright 2000, 2001, 2002, 2003 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"
+#include "longlong.h"
+
+
+/* Don't bloat a shared library with unused code. */
+#if USE_PREINV_DIVREM_1
+
+/* Same test here for skipping one divide step as in mpn_divrem_1.
+
+ The main reason for a separate shift==0 case is that not all CPUs give
+ zero for "n0 >> BITS_PER_MP_LIMB" which would arise in the general case
+ code used on shift==0. shift==0 is also reasonably common in __mp_bases
+ big_base, for instance base==10 on a 64-bit limb.
+
+ Under shift!=0 it would be possible to call mpn_lshift to adjust the
+ dividend all in one go (into the quotient space say), rather than
+ limb-by-limb in the loop. This might help if mpn_lshift is a lot faster
+ than what the compiler can generate for EXTRACT. But this is left to CPU
+ specific implementations to consider, especially since EXTRACT isn't on
+ the dependent chain.
+
+ If size==0 then the result is simply xsize limbs of zeros, but nothing
+ special is done for that, since it wouldn't be a usual call, and
+ certainly never arises from mpn_get_str which is our main caller. */
+
+mp_limb_t
+mpn_preinv_divrem_1 (mp_ptr qp, mp_size_t xsize,
+ mp_srcptr ap, mp_size_t size, mp_limb_t d_unnorm,
+ mp_limb_t dinv, int shift)
+{
+ mp_limb_t ahigh, qhigh, r;
+ mp_size_t i;
+ mp_limb_t n1, n0;
+ mp_limb_t d;
+
+ ASSERT (xsize >= 0);
+ ASSERT (size >= 1);
+ ASSERT (d_unnorm != 0);
+#if WANT_ASSERT
+ {
+ int want_shift;
+ mp_limb_t want_dinv;
+ count_leading_zeros (want_shift, d_unnorm);
+ ASSERT (shift == want_shift);
+ invert_limb (want_dinv, d_unnorm << shift);
+ ASSERT (dinv == want_dinv);
+ }
+#endif
+ /* FIXME: What's the correct overlap rule when xsize!=0? */
+ ASSERT (MPN_SAME_OR_SEPARATE_P (qp+xsize, ap, size));
+
+ ahigh = ap[size-1];
+ d = d_unnorm << shift;
+ qp += (size + xsize - 1); /* dest high limb */
+
+ if (shift == 0)
+ {
+ /* High quotient limb is 0 or 1, and skip a divide step. */
+ r = ahigh;
+ qhigh = (r >= d);
+ r = (qhigh ? r-d : r);
+ *qp-- = qhigh;
+ size--;
+
+ for (i = size-1; i >= 0; i--)
+ {
+ n0 = ap[i];
+ udiv_qrnnd_preinv (*qp, r, r, n0, d, dinv);
+ qp--;
+ }
+ }
+ else
+ {
+ r = 0;
+ if (ahigh < d_unnorm)
+ {
+ r = ahigh << shift;
+ *qp-- = 0;
+ size--;
+ if (size == 0)
+ goto done_integer;
+ }
+
+ n1 = ap[size-1];
+ r |= n1 >> (BITS_PER_MP_LIMB - shift);
+
+ for (i = size-2; i >= 0; i--)
+ {
+ ASSERT (r < d);
+ n0 = ap[i];
+ udiv_qrnnd_preinv (*qp, r, r,
+ ((n1 << shift) | (n0 >> (BITS_PER_MP_LIMB - shift))),
+ d, dinv);
+ qp--;
+ n1 = n0;
+ }
+ udiv_qrnnd_preinv (*qp, r, r, n1 << shift, d, dinv);
+ qp--;
+ }
+
+ done_integer:
+ for (i = 0; i < xsize; i++)
+ {
+ udiv_qrnnd_preinv (*qp, r, r, CNST_LIMB(0), d, dinv);
+ qp--;
+ }
+
+ return r >> shift;
+}
+
+#endif /* USE_PREINV_DIVREM_1 */
projects / msp430-gcc.git / blobdiff