1// Low-level functions for atomic operations: m68k version -*- C++ -*-
2
3// Copyright (C) 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library.  This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 2, or (at your option)
9// any later version.
10
11// This library 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 along
17// with this library; see the file COPYING.  If not, write to the Free
18// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
19// USA.
20
21// As a special exception, you may use this file as part of a free software
22// library without restriction.  Specifically, if other files instantiate
23// templates or use macros or inline functions from this file, or you compile
24// this file and link it with other files to produce an executable, this
25// file does not by itself cause the resulting executable to be covered by
26// the GNU General Public License.  This exception does not however
27// invalidate any other reasons why the executable file might be covered by
28// the GNU General Public License.
29
30#include <ext/atomicity.h>
31
32_GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
33
34#if ( defined(__mc68020__) || defined(__mc68030__) \
35      || defined(__mc68040__) || defined(__mc68060__) ) \
36    && !defined(__mcpu32__)
37  // These variants support compare-and-swap.
38  _Atomic_word
39  __attribute__ ((__unused__))
40  __exchange_and_add(volatile _Atomic_word* __mem, int __val)
41  {
42    register _Atomic_word __result = *__mem;
43    register _Atomic_word __temp;
44    __asm__ __volatile__ ("1: move%.l %0,%1\n\t"
45			  "add%.l %3,%1\n\t"
46			  "cas%.l %0,%1,%2\n\t"
47			  "jne 1b"
48			  : "=d" (__result), "=&d" (__temp), "=m" (*__mem)
49			  : "d" (__val), "0" (__result), "m" (*__mem));
50    return __result;
51  }
52
53#elif defined(__rtems__)
54  // TAS/JBNE is unsafe on systems with strict priority-based scheduling.
55  // Disable interrupts, which we can do only from supervisor mode.
56  _Atomic_word
57  __attribute__ ((__unused__))
58  __exchange_and_add(volatile _Atomic_word* __mem, int __val)
59  {
60    _Atomic_word __result;
61    short __level, __tmpsr;
62    __asm__ __volatile__ ("move%.w %%sr,%0\n\tor%.l %0,%1\n\tmove%.w %1,%%sr"
63			  : "=d"(__level), "=d"(__tmpsr) : "1"(0x700));
64
65    __result = *__mem;
66    *__mem = __result + __val;
67    __asm__ __volatile__ ("move%.w %0,%%sr" : : "d"(__level));
68
69    return __result;
70  }
71
72#else
73
74  template<int __inst>
75    struct _Atomicity_lock
76    {
77      static volatile unsigned char _S_atomicity_lock;
78    };
79
80  template<int __inst>
81  volatile unsigned char _Atomicity_lock<__inst>::_S_atomicity_lock = 0;
82
83  template volatile unsigned char _Atomicity_lock<0>::_S_atomicity_lock;
84
85  _Atomic_word
86  __attribute__ ((__unused__))
87  __exchange_and_add(volatile _Atomic_word* __mem, int __val)
88  {
89    _Atomic_word __result;
90
91    // bset with no immediate addressing (not SMP-safe)
92#if defined(__mcf5200__) || defined(__mcf5300__)
93    __asm__ __volatile__("1: bset.b #7,%0@\n\tjbne 1b"
94			 : /* no outputs */
95			 : "a"(&_Atomicity_lock<0>::_S_atomicity_lock)
96			 : "cc", "memory");
97
98    // CPU32 and MCF5400 support test-and-set (SMP-safe).
99#elif defined(__mcpu32__) || defined(__mcf5400__)
100    __asm__ __volatile__("1: tas %0\n\tjbne 1b"
101			 : "+m"(_Atomicity_lock<0>::_S_atomicity_lock)
102			 : /* none */
103			 : "cc");
104
105    // Use bset with immediate addressing for 68000/68010 (not SMP-safe)
106    // NOTE: TAS is available on the 68000, but unsupported by some Amiga
107    // memory controllers.
108#else
109    __asm__ __volatile__("1: bset.b #7,%0\n\tjbne 1b"
110			 : "+m"(_Atomicity_lock<0>::_S_atomicity_lock)
111			 : /* none */
112			 : "cc");
113#endif
114
115    __result = *__mem;
116    *__mem = __result + __val;
117
118    _Atomicity_lock<0>::_S_atomicity_lock = 0;
119
120    return __result;
121  }
122
123#endif /* TAS / BSET */
124
125  void
126  __attribute__ ((__unused__))
127  __atomic_add(volatile _Atomic_word* __mem, int __val)
128  {
129    // Careful: using add.l with a memory destination is not
130    // architecturally guaranteed to be atomic.
131    __exchange_and_add(__mem, __val);
132  }
133
134_GLIBCXX_END_NAMESPACE
135