mulmid C implementation.

1 files changed, 90 insertions, 0 deletions

diff --git a/mpn/generic/add_err1_n.c b/mpn/generic/add_err1_n.c
new file mode 100644
index 000000000..8ccba7006
--- /dev/null
+++ b/mpn/generic/add_err1_n.c
@@ -0,0 +1,90 @@
+/* mpn_add_err1_n -- add_n with one error term
+
+   Contributed by David Harvey.
+
+   THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE.  IT IS ONLY
+   SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES.  IN FACT, IT IS ALMOST
+   GUARANTEED THAT IT'LL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.
+
+Copyright 2011 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"
+
+/*
+  Computes:
+
+  (1) {rp,n} := {up,n} + {vp,n} (just like mpn_add_n) with incoming carry cy,
+  return value is carry out.
+
+  (2) Let c[i+1] = carry from i-th limb addition (c[0] = cy).
+  Computes c[1]*yp[n-1] + ... + c[n]*yp[0], stores two-limb result at ep.
+
+  Requires n >= 1.
+
+  None of the outputs may overlap each other or any of the inputs, except
+  that {rp,n} may be equal to {up,n} or {vp,n}.
+*/
+mp_limb_t
+mpn_add_err1_n (mp_ptr rp, mp_srcptr up, mp_srcptr vp,
+		mp_ptr ep, mp_srcptr yp,
+                mp_size_t n, mp_limb_t cy)
+{
+  mp_limb_t el, eh, ul, vl, yl, zl, rl, sl, cy1, cy2;
+
+  ASSERT (n >= 1);
+  ASSERT (MPN_SAME_OR_SEPARATE_P (rp, up, n));
+  ASSERT (MPN_SAME_OR_SEPARATE_P (rp, vp, n));
+  ASSERT (! MPN_OVERLAP_P (rp, n, yp, n));
+  ASSERT (! MPN_OVERLAP_P (ep, 2, up, n));
+  ASSERT (! MPN_OVERLAP_P (ep, 2, vp, n));
+  ASSERT (! MPN_OVERLAP_P (ep, 2, yp, n));
+  ASSERT (! MPN_OVERLAP_P (ep, 2, rp, n));
+
+  yp += n - 1;
+  el = eh = 0;
+
+  do
+    {
+      yl = *yp--;
+      ul = *up++;
+      vl = *vp++;
+
+      /* ordinary add_n */
+      ADDC_LIMB (cy1, sl, ul, vl);
+      ADDC_LIMB (cy2, rl, sl, cy);
+      cy = cy1 | cy2;
+      *rp++ = rl;
+
+      /* update (eh:el) */
+      zl = (-cy) & yl;
+      el += zl;
+      eh += el < zl;
+    }
+  while (--n);
+
+#if GMP_NAIL_BITS != 0
+  eh = (eh << GMP_NAIL_BITS) + (el >> GMP_NUMB_BITS);
+  el &= GMP_NUMB_MASK;
+#endif
+
+  ep[0] = el;
+  ep[1] = eh;
+
+  return cy;
+}