1 // Low-level functions for atomic operations: m68k version -*- C++ -*-
2 
3 // Copyright (C) 2001-2019 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