libgcc/ashrdi3.c

   1 /* ashrdi3.c extracted from gcc-2.7.2/libgcc2.c which is: */
   2 /* Copyright (C) 1989, 1992, 1993, 1994, 1995 Free Software Foundation, Inc.
   3
   4 This file is part of GNU CC.
   5
   6 GNU CC is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU CC is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU CC; see the file COPYING.  If not, write to
  18 the Free Software Foundation, 51 Franklin St, Fifth Floor, Boston,
  19 MA 02110-1301, USA. */
  20
  21 #include "libgcc.h"
  22
  23 #define BITS_PER_UNIT 8
  24
  25 struct DIstruct {SItype high, low;};
  26
  27 typedef union
  28 {
  29   struct DIstruct s;
  30   DItype ll;
  31 } DIunion;
  32
  33 DItype
  34 __ashrdi3 (DItype u, word_type b)
  35 {
  36   DIunion w;
  37   word_type bm;
  38   DIunion uu;
  39
  40   if (b == 0)
  41     return u;
  42
  43   uu.ll = u;
  44
  45   bm = (sizeof (SItype) * BITS_PER_UNIT) - b;
  46   if (bm <= 0)
  47     {
  48       /* w.s.high = 1..1 or 0..0 */
  49       w.s.high = uu.s.high >> (sizeof (SItype) * BITS_PER_UNIT - 1);
  50       w.s.low = uu.s.high >> -bm;
  51     }
  52   else
  53     {
  54       USItype carries = (USItype)uu.s.high << bm;
  55       w.s.high = uu.s.high >> b;
  56       w.s.low = ((USItype)uu.s.low >> b) | carries;
  57     }
  58
  59   return w.ll;
  60 }