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lshrdi3.c
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1 /* lshrdi3.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, 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA. */
20 
21 #define BITS_PER_UNIT 8
22 
23 typedef int SItype __attribute__ ((mode (SI)));
24 typedef unsigned int USItype __attribute__ ((mode (SI)));
25 typedef int DItype __attribute__ ((mode (DI)));
26 typedef int word_type __attribute__ ((mode (__word__)));
27 
28 struct DIstruct {SItype high, low;};
29 
30 typedef union
31 {
32  struct DIstruct s;
33  DItype ll;
34 } DIunion;
35 
36 DItype
37 __lshrdi3 (DItype u, word_type b)
38 {
39  DIunion w;
40  word_type bm;
41  DIunion uu;
42 
43  if (b == 0)
44  return u;
45 
46  uu.ll = u;
47 
48  bm = (sizeof (SItype) * BITS_PER_UNIT) - b;
49  if (bm <= 0)
50  {
51  w.s.high = 0;
52  w.s.low = (USItype)uu.s.high >> -bm;
53  }
54  else
55  {
56  USItype carries = (USItype)uu.s.high << bm;
57  w.s.high = (USItype)uu.s.high >> b;
58  w.s.low = ((USItype)uu.s.low >> b) | carries;
59  }
60 
61  return w.ll;
62 }