Imported gcc-4.4.3

[msp430-gcc.git] / gmp / mpn / generic / binvert.c

diff --git a/gmp/mpn/generic/binvert.c b/gmp/mpn/generic/binvert.c
new file mode 100644 (file)
index 0000000..24d4dcd
--- /dev/null
+++ b/gmp/mpn/generic/binvert.c
@@ -0,0 +1,117 @@
+/* Compute {up,n}^(-1) mod 2(n*GMP_NUMB_BITS).
+
+   Contributed to the GNU project by Torbjorn 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 (C) 2004, 2005, 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"
+
+
+/*
+  r[k+1] = r[k] - r[k] * (u*r[k] - 1)
+  r[k+1] = r[k] + r[k] - r[k]*(u*r[k])
+*/
+
+/* This is intended for constant THRESHOLDs only, where the compiler can
+   completely fold the result.  */
+#define LOG2C(n) \
+ (((n) >=    0x1) + ((n) >=    0x2) + ((n) >=    0x4) + ((n) >=    0x8) + \
+  ((n) >=   0x10) + ((n) >=   0x20) + ((n) >=   0x40) + ((n) >=   0x80) + \
+  ((n) >=  0x100) + ((n) >=  0x200) + ((n) >=  0x400) + ((n) >=  0x800) + \
+  ((n) >= 0x1000) + ((n) >= 0x2000) + ((n) >= 0x4000) + ((n) >= 0x8000))
+
+#if TUNE_PROGRAM_BUILD
+#define NPOWS \
+ ((sizeof(mp_size_t) > 6 ? 48 : 8*sizeof(mp_size_t)))
+#else
+#define NPOWS \
+ ((sizeof(mp_size_t) > 6 ? 48 : 8*sizeof(mp_size_t)) - LOG2C (BINV_NEWTON_THRESHOLD))
+#endif
+
+mp_size_t
+mpn_binvert_itch (mp_size_t n)
+{
+#if WANT_FFT
+  if (ABOVE_THRESHOLD (n, 2 * MUL_FFT_MODF_THRESHOLD))
+    return mpn_fft_next_size (n, mpn_fft_best_k (n, 0));
+  else
+#endif
+    return 3 * (n - (n >> 1));
+}
+
+void
+mpn_binvert (mp_ptr rp, mp_srcptr up, mp_size_t n, mp_ptr scratch)
+{
+  mp_ptr xp;
+  mp_size_t rn, newrn;
+  mp_size_t sizes[NPOWS], *sizp;
+  mp_limb_t di;
+
+  /* Compute the computation precisions from highest to lowest, leaving the
+     base case size in 'rn'.  */
+  sizp = sizes;
+  for (rn = n; ABOVE_THRESHOLD (rn, BINV_NEWTON_THRESHOLD); rn = (rn + 1) >> 1)
+    *sizp++ = rn;
+
+  xp = scratch;
+
+  /* Compute a base value using a low-overhead O(n^2) algorithm.  FIXME: We
+     should call some divide-and-conquer lsb division function here for an
+     operand subrange.  */
+  MPN_ZERO (xp, rn);
+  xp[0] = 1;
+  binvert_limb (di, up[0]);
+  if (BELOW_THRESHOLD (rn, DC_BDIV_Q_THRESHOLD))
+    mpn_sb_bdiv_q (rp, xp, rn, up, rn, -di);
+  else
+    mpn_dc_bdiv_q (rp, xp, rn, up, rn, -di);
+
+  /* Use Newton iterations to get the desired precision.  */
+  for (; rn < n; rn = newrn)
+    {
+      newrn = *--sizp;
+
+#if WANT_FFT
+      if (ABOVE_THRESHOLD (newrn, 2 * MUL_FFT_MODF_THRESHOLD))
+       {
+         int k;
+         mp_size_t m, i;
+
+         k = mpn_fft_best_k (newrn, 0);
+         m = mpn_fft_next_size (newrn, k);
+         mpn_mul_fft (xp, m, up, newrn, rp, rn, k);
+         for (i = rn - 1; i >= 0; i--)
+           if (xp[i] > (i == 0))
+             {
+               mpn_add_1 (xp + rn, xp + rn, newrn - rn, 1);
+               break;
+             }
+       }
+      else
+#endif
+       mpn_mul (xp, up, newrn, rp, rn);
+      mpn_mullow_n (rp + rn, rp, xp + rn, newrn - rn);
+      mpn_neg_n (rp + rn, rp + rn, newrn - rn);
+    }
+}