1 // Low-level functions for atomic operations: m68k version -*- C++ -*- 2 3 // Copyright (C) 2001-2013 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 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 // TAS/JBNE is unsafe on systems with strict priority-based scheduling. 52 // Disable interrupts, which we can do only from supervisor mode. 53 _Atomic_word 54 __attribute__ ((__unused__)) 55 __exchange_and_add(volatile _Atomic_word* __mem, int __val) throw () 56 { 57 _Atomic_word __result; 58 short __level, __tmpsr; 59 __asm__ __volatile__ ("move%.w %%sr,%0\n\tor%.l %0,%1\n\tmove%.w %1,%%sr" 60 : "=d"(__level), "=d"(__tmpsr) : "1"(0x700)); 61 62 __result = *__mem; 63 *__mem = __result + __val; 64 __asm__ __volatile__ ("move%.w %0,%%sr" : : "d"(__level)); 65 66 return __result; 67 } 68 69 #else 70 71 template<int __inst> 72 struct _Atomicity_lock 73 { 74 static volatile unsigned char _S_atomicity_lock; 75 }; 76 77 template<int __inst> 78 volatile unsigned char _Atomicity_lock<__inst>::_S_atomicity_lock = 0; 79 80 template volatile unsigned char _Atomicity_lock<0>::_S_atomicity_lock; 81 82 _Atomic_word 83 __attribute__ ((__unused__)) 84 __exchange_and_add(volatile _Atomic_word* __mem, int __val) throw () 85 { 86 _Atomic_word __result; 87 88 // bset with no immediate addressing (not SMP-safe) 89 #if defined(__mcfisaa__) || defined(__mcfisaaplus__) 90 __asm__ __volatile__("1: bset.b #7,%0@\n\tjbne 1b" 91 : /* no outputs */ 92 : "a"(&_Atomicity_lock<0>::_S_atomicity_lock) 93 : "cc", "memory"); 94 95 // CPU32 and CF ISAs B & C support test-and-set (SMP-safe). 96 #elif defined(__mcpu32__) || defined(__mcfisab__) || defined (__mcfisac__) 97 __asm__ __volatile__("1: tas %0\n\tjbne 1b" 98 : "+m"(_Atomicity_lock<0>::_S_atomicity_lock) 99 : /* none */ 100 : "cc"); 101 102 // Use bset with immediate addressing for 68000/68010 (not SMP-safe) 103 // NOTE: TAS is available on the 68000, but unsupported by some Amiga 104 // memory controllers. 105 #else 106 __asm__ __volatile__("1: bset.b #7,%0\n\tjbne 1b" 107 : "+m"(_Atomicity_lock<0>::_S_atomicity_lock) 108 : /* none */ 109 : "cc"); 110 #endif 111 112 __result = *__mem; 113 *__mem = __result + __val; 114 115 _Atomicity_lock<0>::_S_atomicity_lock = 0; 116 117 return __result; 118 } 119 120 #endif /* TAS / BSET */ 121 122 void 123 __attribute__ ((__unused__)) 124 __atomic_add(volatile _Atomic_word* __mem, int __val) throw () 125 { 126 // Careful: using add.l with a memory destination is not 127 // architecturally guaranteed to be atomic. 128 __exchange_and_add(__mem, __val); 129 } 130 131 _GLIBCXX_END_NAMESPACE_VERSION 132 } // namespace 133