Imported gcc-4.4.3

[msp430-gcc.git] / gmp / mpn / cray / sub_n.c

diff --git a/gmp/mpn/cray/sub_n.c b/gmp/mpn/cray/sub_n.c
new file mode 100644 (file)
index 0000000..90a5f1b
--- /dev/null
+++ b/gmp/mpn/cray/sub_n.c
@@ -0,0 +1,80 @@
+/* Cray PVP mpn_sub_n -- subtract two limb vectors and store their difference
+   in a third limb vector.
+
+Copyright 1996, 2000, 2001 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/.  */
+
+/* This code runs at 4 cycles/limb.  It may be possible to bring it down
+   to 3 cycles/limb.  */
+
+#include "gmp.h"
+#include "gmp-impl.h"
+
+mp_limb_t
+mpn_sub_n (mp_ptr rp, mp_srcptr up, mp_srcptr vp, mp_size_t n)
+{
+  mp_limb_t cy[n];
+  mp_limb_t a, b, r, s0, c0, c1;
+  mp_size_t i;
+  int more_carries;
+
+  /* Main subtract loop.  Generate a raw output difference in rp[] and a
+     borrow vector in cy[].  */
+#pragma _CRI ivdep
+  for (i = 0; i < n; i++)
+    {
+      a = up[i];
+      b = vp[i];
+      s0 = a - b;              /* a = s0 + b */
+      rp[i] = s0;
+      c0 = ((s0 & b) | ((s0 | b) & ~a)) >> 63;
+      cy[i] = c0;
+    }
+  /* Borrow subtract loop.  Subtract the borrow vector cy[] from the raw
+     difference rp[] and store the new difference back to rp[0].  If this
+     generates further borrow, set more_carries.  */
+  more_carries = 0;
+#pragma _CRI ivdep
+  for (i = 1; i < n; i++)
+    {
+      r = rp[i];
+      c0 = cy[i - 1];
+      s0 = r - c0;             /* r = s0 + c0 */
+      rp[i] = s0;
+      c0 = (s0 & ~r) >> 63;
+      more_carries += c0;
+    }
+  /* If that second loop generated borrow, handle that in scalar loop.  */
+  if (more_carries)
+    {
+      mp_limb_t cyrec = 0;
+      /* Look for places where rp[k] contains just ones and cy[k-1] is
+        non-zero.  These are where we got a recurrency borrow.  */
+      for (i = 1; i < n; i++)
+       {
+         r = rp[i];
+         c0 = (~r == 0 && cy[i - 1] != 0);
+         s0 = r - cyrec;
+         rp[i] = s0;
+         c1 = (s0 & ~r) >> 63;
+         cyrec = c0 | c1;
+       }
+      return cyrec | cy[n - 1];
+    }
+
+  return cy[n - 1];
+}