Imported gcc-4.4.3

[msp430-gcc.git] / gmp / mpz / cfdiv_r_2exp.c

diff --git a/gmp/mpz/cfdiv_r_2exp.c b/gmp/mpz/cfdiv_r_2exp.c
new file mode 100644 (file)
index 0000000..005779f
--- /dev/null
+++ b/gmp/mpz/cfdiv_r_2exp.c
@@ -0,0 +1,155 @@
+/* mpz_cdiv_r_2exp, mpz_fdiv_r_2exp -- remainder from mpz divided by 2^n.
+
+Copyright 2001, 2002, 2004 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"
+
+
+/* Bit mask of "n" least significant bits of a limb. */
+#define LOW_MASK(n)   ((CNST_LIMB(1) << (n)) - 1)
+
+
+/* dir==1 for ceil, dir==-1 for floor */
+
+static void __gmpz_cfdiv_r_2exp __GMP_PROTO ((REGPARM_3_1 (mpz_ptr w, mpz_srcptr u, unsigned long cnt, int dir))) REGPARM_ATTR (1);
+#define cfdiv_r_2exp(w,u,cnt,dir)  __gmpz_cfdiv_r_2exp (REGPARM_3_1 (w, u, cnt, dir))
+
+REGPARM_ATTR (1) static void
+cfdiv_r_2exp (mpz_ptr w, mpz_srcptr u, unsigned long cnt, int dir)
+{
+  mp_size_t  usize, abs_usize, limb_cnt, i;
+  mp_srcptr  up;
+  mp_ptr     wp;
+  mp_limb_t  high;
+
+  usize = SIZ(u);
+  if (usize == 0)
+    {
+      SIZ(w) = 0;
+      return;
+    }
+
+  limb_cnt = cnt / GMP_NUMB_BITS;
+  cnt %= GMP_NUMB_BITS;
+  abs_usize = ABS (usize);
+
+  /* MPZ_REALLOC(w) below is only when w!=u, so we can fetch PTR(u) here
+     nice and early */
+  up = PTR(u);
+
+  if ((usize ^ dir) < 0)
+    {
+      /* Round towards zero, means just truncate */
+
+      if (w == u)
+        {
+          /* if already smaller than limb_cnt then do nothing */
+          if (abs_usize <= limb_cnt)
+            return;
+          wp = PTR(w);
+        }
+      else
+        {
+          i = MIN (abs_usize, limb_cnt+1);
+          MPZ_REALLOC (w, i);
+          wp = PTR(w);
+          MPN_COPY (wp, up, i);
+
+          /* if smaller than limb_cnt then only the copy is needed */
+          if (abs_usize <= limb_cnt)
+            {
+              SIZ(w) = usize;
+              return;
+            }
+        }
+    }
+  else
+    {
+      /* Round away from zero, means twos complement if non-zero */
+
+      /* if u!=0 and smaller than divisor, then must negate */
+      if (abs_usize <= limb_cnt)
+        goto negate;
+
+      /* if non-zero low limb, then must negate */
+      for (i = 0; i < limb_cnt; i++)
+        if (up[i] != 0)
+          goto negate;
+
+      /* if non-zero partial limb, then must negate */
+      if ((up[limb_cnt] & LOW_MASK (cnt)) != 0)
+        goto negate;
+
+      /* otherwise low bits of u are zero, so that's the result */
+      SIZ(w) = 0;
+      return;
+
+    negate:
+      /* twos complement negation to get 2**cnt-u */
+
+      MPZ_REALLOC (w, limb_cnt+1);
+      up = PTR(u);
+      wp = PTR(w);
+
+      /* Ones complement */
+      i = MIN (abs_usize, limb_cnt+1);
+      mpn_com_n (wp, up, i);
+      for ( ; i <= limb_cnt; i++)
+        wp[i] = GMP_NUMB_MAX;
+
+      /* Twos complement.  Since u!=0 in the relevant part, the twos
+         complement never gives 0 and a carry, so can use MPN_INCR_U. */
+      MPN_INCR_U (wp, limb_cnt+1, CNST_LIMB(1));
+
+      usize = -usize;
+    }
+
+  /* Mask the high limb */
+  high = wp[limb_cnt];
+  high &= LOW_MASK (cnt);
+  wp[limb_cnt] = high;
+
+  /* Strip any consequent high zeros */
+  while (high == 0)
+    {
+      limb_cnt--;
+      if (limb_cnt < 0)
+        {
+          SIZ(w) = 0;
+          return;
+        }
+      high = wp[limb_cnt];
+    }
+
+  limb_cnt++;
+  SIZ(w) = (usize >= 0 ? limb_cnt : -limb_cnt);
+}
+
+
+void
+mpz_cdiv_r_2exp (mpz_ptr w, mpz_srcptr u, unsigned long cnt)
+{
+  cfdiv_r_2exp (w, u, cnt, 1);
+}
+
+void
+mpz_fdiv_r_2exp (mpz_ptr w, mpz_srcptr u, unsigned long cnt)
+{
+  cfdiv_r_2exp (w, u, cnt, -1);
+}