1 // Low-level functions for atomic operations: m68k version -*- C++ -*-
2
3 // Copyright (C) 2001-2021 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 3, 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 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24
25 #include <ext/atomicity.h>
26
_GLIBCXX_VISIBILITY(default)27 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
28 {
29 _GLIBCXX_BEGIN_NAMESPACE_VERSION
30
31 #if ( defined(__mc68020__) || defined(__mc68030__) \
32 || defined(__mc68040__) || defined(__mc68060__) ) \
33 && !defined(__mcpu32__)
34 // These variants support compare-and-swap.
35 _Atomic_word
36 __attribute__ ((__unused__))
37 __exchange_and_add(volatile _Atomic_word* __mem, int __val) throw ()
38 {
39 register _Atomic_word __result = *__mem;
40 register _Atomic_word __temp;
41 __asm__ __volatile__ ("1: move%.l %0,%1\n\t"
42 "add%.l %3,%1\n\t"
43 "cas%.l %0,%1,%2\n\t"
44 "jne 1b"
45 : "=d" (__result), "=&d" (__temp), "=m" (*__mem)
46 : "d" (__val), "0" (__result), "m" (*__mem));
47 return __result;
48 }
49
50 #elif defined(__rtems__)
51 // This code is only provided for reference. RTEMS uses now the atomic
52 // builtins and libatomic. See configure.host.
53 //
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) throw ()
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) throw ()
88 {
89 _Atomic_word __result;
90
91 // bset with no immediate addressing (not SMP-safe)
92 #if defined(__mcfisaa__) || defined(__mcfisaaplus__)
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 CF ISAs B & C support test-and-set (SMP-safe).
99 #elif defined(__mcpu32__) || defined(__mcfisab__) || defined (__mcfisac__)
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) throw ()
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_VERSION
135 } // namespace
136