1 // Low-level functions for atomic operations: m68k version -*- C++ -*-
2
3 // Copyright (C) 2001, 2002, 2003 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, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
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 #ifndef _BITS_ATOMICITY_H
31 #define _BITS_ATOMICITY_H 1
32
33 typedef int _Atomic_word;
34
35 #if ( defined(__mc68020__) || defined(__mc68030__) \
36 || defined(__mc68040__) || defined(__mc68060__) ) \
37 && !defined(__mcpu32__)
38 // These variants support compare-and-swap.
39
40 static inline _Atomic_word
41 __attribute__ ((__unused__))
__exchange_and_add(volatile _Atomic_word * __mem,int __val)42 __exchange_and_add (volatile _Atomic_word *__mem, int __val)
43 {
44 register _Atomic_word __result = *__mem;
45 register _Atomic_word __temp;
46 __asm__ __volatile__ ("1: move%.l %0,%1\n\t"
47 "add%.l %2,%1\n\t"
48 "cas%.l %0,%1,%3\n\t"
49 "jne 1b"
50 : "=d" (__result), "=&d" (__temp)
51 : "d" (__val), "m" (*__mem), "0" (__result)
52 : "memory");
53 return __result;
54 }
55
56 #elif defined(__rtems__)
57 /*
58 * TAS/JBNE is unsafe on systems with strict priority-based scheduling.
59 * Disable interrupts, which we can do only from supervisor mode.
60 */
61 static inline _Atomic_word
62 __attribute__ ((__unused__))
__exchange_and_add(volatile _Atomic_word * __mem,int __val)63 __exchange_and_add (volatile _Atomic_word *__mem, int __val)
64 {
65 _Atomic_word __result;
66 short __level, __tmpsr;
67 __asm__ __volatile__ ("move%.w %%sr,%0\n\tor%.l %0,%1\n\tmove%.w %1,%%sr"
68 : "=d"(__level), "=d"(__tmpsr) : "1"(0x700));
69
70 __result = *__mem;
71 *__mem = __result + __val;
72
73 __asm__ __volatile__ ("move%.w %0,%%sr" : : "d"(__level));
74
75 return __result;
76 }
77
78 #else
79
80 template <int __inst>
81 struct __Atomicity_lock
82 {
83 static volatile unsigned char _S_atomicity_lock;
84 };
85
86 template <int __inst>
87 volatile unsigned char __Atomicity_lock<__inst>::_S_atomicity_lock = 0;
88
89 template volatile unsigned char __Atomicity_lock<0>::_S_atomicity_lock;
90
91 static inline _Atomic_word
92 __attribute__ ((__unused__))
__exchange_and_add(volatile _Atomic_word * __mem,int __val)93 __exchange_and_add (volatile _Atomic_word *__mem, int __val)
94 {
95 _Atomic_word __result;
96
97 // bset with no immediate addressing
98 #if defined(__mcf5200__) || defined(__mcf5300__) || defined(__mcf5400__)
99 __asm__ __volatile__("1: bset.b #7,%0@\n\tjbne 1b"
100 : /* no outputs */
101 : "a"(&__Atomicity_lock<0>::_S_atomicity_lock)
102 : "cc", "memory");
103
104 // bset with immediate addressing
105 #elif defined(__mc68000__)
106 __asm__ __volatile__("1: bset.b #7,%0\n\tjbne 1b"
107 : "+m"(__Atomicity_lock<0>::_S_atomicity_lock)
108 : /* none */
109 : "cc");
110
111 #else // 680x0, cpu32, 5400 support test-and-set.
112 __asm__ __volatile__("1: tas %0\n\tjbne 1b"
113 : "+m"(__Atomicity_lock<0>::_S_atomicity_lock)
114 : /* none */
115 : "cc");
116 #endif
117
118 __result = *__mem;
119 *__mem = __result + __val;
120
121 __Atomicity_lock<0>::_S_atomicity_lock = 0;
122
123 return __result;
124 }
125
126 #endif /* TAS / BSET */
127
128 static inline void
129 __attribute__ ((__unused__))
__atomic_add(volatile _Atomic_word * __mem,int __val)130 __atomic_add (volatile _Atomic_word* __mem, int __val)
131 {
132 // Careful: using add.l with a memory destination is not
133 // architecturally guaranteed to be atomic.
134 (void) __exchange_and_add (__mem, __val);
135 }
136
137 #endif /* _BITS_ATOMICITY_H */
138