[project @ 1996-01-08 20:28:12 by partain]

[ghc-hetmet.git] / ghc / runtime / gmp / mpn_add.c

diff --git a/ghc/runtime/gmp/mpn_add.c b/ghc/runtime/gmp/mpn_add.c
new file mode 100644 (file)
index 0000000..10502a8
--- /dev/null
+++ b/ghc/runtime/gmp/mpn_add.c
@@ -0,0 +1,141 @@
+/* mpn_add -- Add two low-level integers.
+
+Copyright (C) 1991 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 General Public License as published by
+the Free Software Foundation; either version 2, 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 General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with the GNU MP Library; see the file COPYING.  If not, write to
+the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
+
+#include "gmp.h"
+#include "gmp-impl.h"
+
+/* Add ADD1_PTR/ADD1_SIZE and ADD2_PTR/ADD2_SIZE and store the first
+   ADD1_SIZE words of the result at SUM_PTR.
+
+   Return 1 if carry out was generated, return 0 otherwise.
+
+   Argument constraint: ADD1_SIZE >= ADD2_SIZE.
+
+   The size of SUM can be calculated as ADD1_SIZE + the return value.  */
+
+mp_limb
+#ifdef __STDC__
+mpn_add (mp_ptr sum_ptr,
+        mp_srcptr add1_ptr, mp_size add1_size,
+        mp_srcptr add2_ptr, mp_size add2_size)
+#else
+mpn_add (sum_ptr, add1_ptr, add1_size, add2_ptr, add2_size)
+     mp_ptr sum_ptr;
+     mp_srcptr add1_ptr;
+     mp_size add1_size;
+     mp_srcptr add2_ptr;
+     mp_size add2_size;
+#endif
+{
+  mp_limb a1, a2, sum;
+  mp_size j;
+
+  /* The loop counter and index J goes from some negative value to zero.
+     This way the loops become faster.  Need to offset the base pointers
+     to take care of the negative indices.  */
+
+  j = -add2_size;
+  if (j == 0)
+    goto add2_finished;
+
+  add1_ptr -= j;
+  add2_ptr -= j;
+  sum_ptr -= j;
+
+  /* There are two do-loops, marked NON-CARRY LOOP and CARRY LOOP that
+     jump between each other.  The first loop is for when the previous
+     addition didn't produce a carry-out; the second is for the
+     complementary case.  */
+
+  /* NON-CARRY LOOP */
+  do
+    {
+      a1 = add1_ptr[j];
+      a2 = add2_ptr[j];
+      sum = a1 + a2;
+      sum_ptr[j] = sum;
+      if (sum < a2)
+       goto cy_loop;
+    ncy_loop:
+      j++;
+    }
+  while (j < 0);
+
+  /* We have exhausted ADD2.  Just copy ADD1 to SUM, and return
+     0 as an indication of no carry-out.  */
+
+ add2_finished:
+  /* Immediate return if the copy would be a no-op.  */
+  if (sum_ptr == add1_ptr)
+    return 0;
+
+  j = add2_size - add1_size;
+  add1_ptr -= j;
+  sum_ptr -= j;
+
+  while (j < 0)
+    {
+      sum_ptr[j] = add1_ptr[j];
+      j++;
+    }
+  return 0;
+
+  /* CARRY LOOP */
+  do
+    {
+      a1 = add1_ptr[j];
+      a2 = add2_ptr[j];
+      sum = a1 + a2 + 1;
+      sum_ptr[j] = sum;
+      if (sum > a2)
+       goto ncy_loop;
+    cy_loop:
+      j++;
+    }
+  while (j < 0);
+
+  j = add2_size - add1_size;
+  add1_ptr -= j;
+  sum_ptr -= j;
+
+  while (j < 0)
+    {
+      a1 = add1_ptr[j];
+      sum = a1 + 1;
+      sum_ptr[j] = sum;
+      if (sum > 0)
+       goto copy_add1;
+      j++;
+    }
+  return 1;
+
+ copy_add1:
+  if (sum_ptr == add1_ptr)
+    return 0;
+
+  j++;
+  while (j < 0)
+    {
+      sum_ptr[j] = add1_ptr[j];
+      j++;
+    }
+
+  return 0;
+}