--- /dev/null
+/* mpn_mod_1(dividend_ptr, dividend_size, divisor_limb) --
+ Divide (DIVIDEND_PTR,,DIVIDEND_SIZE) by DIVISOR_LIMB.
+ Return the single-limb remainder.
+ There are no constraints on the value of the divisor.
+
+Copyright 1991, 1993, 1994, 1999, 2000, 2002, 2007, 2008, 2009 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"
+
+
+/* The size where udiv_qrnnd_preinv should be used rather than udiv_qrnnd,
+ meaning the quotient size where that should happen, the quotient size
+ being how many udiv divisions will be done.
+
+ The default is to use preinv always, CPUs where this doesn't suit have
+ tuned thresholds. Note in particular that preinv should certainly be
+ used if that's the only division available (USE_PREINV_ALWAYS). */
+
+#ifndef MOD_1_NORM_THRESHOLD
+#define MOD_1_NORM_THRESHOLD 0
+#endif
+
+#ifndef MOD_1_UNNORM_THRESHOLD
+#define MOD_1_UNNORM_THRESHOLD 0
+#endif
+
+#ifndef MOD_1_1_THRESHOLD
+#define MOD_1_1_THRESHOLD MP_SIZE_T_MAX /* default is not to use mpn_mod_1s */
+#endif
+
+#ifndef MOD_1_2_THRESHOLD
+#define MOD_1_2_THRESHOLD 10
+#endif
+
+#ifndef MOD_1_4_THRESHOLD
+#define MOD_1_4_THRESHOLD 120
+#endif
+
+
+/* The comments in mpn/generic/divrem_1.c apply here too.
+
+ As noted in the algorithms section of the manual, the shifts in the loop
+ for the unnorm case can be avoided by calculating r = a%(d*2^n), followed
+ by a final (r*2^n)%(d*2^n). In fact if it happens that a%(d*2^n) can
+ skip a division where (a*2^n)%(d*2^n) can't then there's the same number
+ of divide steps, though how often that happens depends on the assumed
+ distributions of dividend and divisor. In any case this idea is left to
+ CPU specific implementations to consider. */
+
+static mp_limb_t
+mpn_mod_1_unnorm (mp_srcptr up, mp_size_t un, mp_limb_t d)
+{
+ mp_size_t i;
+ mp_limb_t n1, n0, r;
+ mp_limb_t dummy;
+ int cnt;
+
+ ASSERT (un > 0);
+ ASSERT (d != 0);
+
+ d <<= GMP_NAIL_BITS;
+
+ /* Skip a division if high < divisor. Having the test here before
+ normalizing will still skip as often as possible. */
+ r = up[un - 1] << GMP_NAIL_BITS;
+ if (r < d)
+ {
+ r >>= GMP_NAIL_BITS;
+ un--;
+ if (un == 0)
+ return r;
+ }
+ else
+ r = 0;
+
+ /* If udiv_qrnnd doesn't need a normalized divisor, can use the simple
+ code above. */
+ if (! UDIV_NEEDS_NORMALIZATION
+ && BELOW_THRESHOLD (un, MOD_1_UNNORM_THRESHOLD))
+ {
+ for (i = un - 1; i >= 0; i--)
+ {
+ n0 = up[i] << GMP_NAIL_BITS;
+ udiv_qrnnd (dummy, r, r, n0, d);
+ r >>= GMP_NAIL_BITS;
+ }
+ return r;
+ }
+
+ count_leading_zeros (cnt, d);
+ d <<= cnt;
+
+ n1 = up[un - 1] << GMP_NAIL_BITS;
+ r = (r << cnt) | (n1 >> (GMP_LIMB_BITS - cnt));
+
+ if (UDIV_NEEDS_NORMALIZATION
+ && BELOW_THRESHOLD (un, MOD_1_UNNORM_THRESHOLD))
+ {
+ for (i = un - 2; i >= 0; i--)
+ {
+ n0 = up[i] << GMP_NAIL_BITS;
+ udiv_qrnnd (dummy, r, r,
+ (n1 << cnt) | (n0 >> (GMP_NUMB_BITS - cnt)),
+ d);
+ r >>= GMP_NAIL_BITS;
+ n1 = n0;
+ }
+ udiv_qrnnd (dummy, r, r, n1 << cnt, d);
+ r >>= GMP_NAIL_BITS;
+ return r >> cnt;
+ }
+ else
+ {
+ mp_limb_t inv;
+ invert_limb (inv, d);
+
+ for (i = un - 2; i >= 0; i--)
+ {
+ n0 = up[i] << GMP_NAIL_BITS;
+ udiv_qrnnd_preinv (dummy, r, r,
+ (n1 << cnt) | (n0 >> (GMP_NUMB_BITS - cnt)),
+ d, inv);
+ r >>= GMP_NAIL_BITS;
+ n1 = n0;
+ }
+ udiv_qrnnd_preinv (dummy, r, r, n1 << cnt, d, inv);
+ r >>= GMP_NAIL_BITS;
+ return r >> cnt;
+ }
+}
+
+static mp_limb_t
+mpn_mod_1_norm (mp_srcptr up, mp_size_t un, mp_limb_t d)
+{
+ mp_size_t i;
+ mp_limb_t n0, r;
+ mp_limb_t dummy;
+
+ ASSERT (un > 0);
+
+ d <<= GMP_NAIL_BITS;
+
+ ASSERT (d & GMP_LIMB_HIGHBIT);
+
+ /* High limb is initial remainder, possibly with one subtract of
+ d to get r<d. */
+ r = up[un - 1] << GMP_NAIL_BITS;
+ if (r >= d)
+ r -= d;
+ r >>= GMP_NAIL_BITS;
+ un--;
+ if (un == 0)
+ return r;
+
+ if (BELOW_THRESHOLD (un, MOD_1_NORM_THRESHOLD))
+ {
+ for (i = un - 1; i >= 0; i--)
+ {
+ n0 = up[i] << GMP_NAIL_BITS;
+ udiv_qrnnd (dummy, r, r, n0, d);
+ r >>= GMP_NAIL_BITS;
+ }
+ return r;
+ }
+ else
+ {
+ mp_limb_t inv;
+ invert_limb (inv, d);
+ for (i = un - 1; i >= 0; i--)
+ {
+ n0 = up[i] << GMP_NAIL_BITS;
+ udiv_qrnnd_preinv (dummy, r, r, n0, d, inv);
+ r >>= GMP_NAIL_BITS;
+ }
+ return r;
+ }
+}
+
+mp_limb_t
+mpn_mod_1 (mp_srcptr ap, mp_size_t n, mp_limb_t b)
+{
+ ASSERT (n >= 0);
+ ASSERT (b != 0);
+
+ /* Should this be handled at all? Rely on callers? Note un==0 is currently
+ required by mpz/fdiv_r_ui.c and possibly other places. */
+ if (n == 0)
+ return 0;
+
+ if (UNLIKELY ((b & GMP_NUMB_HIGHBIT) != 0))
+ {
+ /* The functions below do not handle this large divisor. */
+ return mpn_mod_1_norm (ap, n, b);
+ }
+ else if (BELOW_THRESHOLD (n, MOD_1_1_THRESHOLD))
+ {
+ return mpn_mod_1_unnorm (ap, n, b);
+ }
+ else if (BELOW_THRESHOLD (n, MOD_1_2_THRESHOLD))
+ {
+ mp_limb_t pre[4];
+ mpn_mod_1s_1p_cps (pre, b);
+ return mpn_mod_1s_1p (ap, n, b << pre[1], pre);
+ }
+ else if (BELOW_THRESHOLD (n, MOD_1_4_THRESHOLD) || UNLIKELY (b > GMP_NUMB_MASK / 4))
+ {
+ mp_limb_t pre[5];
+ mpn_mod_1s_2p_cps (pre, b);
+ return mpn_mod_1s_2p (ap, n, b << pre[1], pre);
+ }
+ else
+ {
+ mp_limb_t pre[7];
+ mpn_mod_1s_4p_cps (pre, b);
+ return mpn_mod_1s_4p (ap, n, b << pre[1], pre);
+ }
+}
projects / msp430-gcc.git / blobdiff