1 // Low-level functions for atomic operations: m68k version -*- C++ -*- 2 3 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2009 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 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx) 28 29 #if ( defined(__mc68020__) || defined(__mc68030__) \ 30 || defined(__mc68040__) || defined(__mc68060__) ) \ 31 && !defined(__mcpu32__) 32 // These variants support compare-and-swap. 33 _Atomic_word 34 __attribute__ ((__unused__)) 35 __exchange_and_add(volatile _Atomic_word* __mem, int __val) throw () 36 { 37 register _Atomic_word __result = *__mem; 38 register _Atomic_word __temp; 39 __asm__ __volatile__ ("1: move%.l %0,%1\n\t" 40 "add%.l %3,%1\n\t" 41 "cas%.l %0,%1,%2\n\t" 42 "jne 1b" 43 : "=d" (__result), "=&d" (__temp), "=m" (*__mem) 44 : "d" (__val), "0" (__result), "m" (*__mem)); 45 return __result; 46 } 47 48 #elif defined(__rtems__) 49 // TAS/JBNE is unsafe on systems with strict priority-based scheduling. 50 // Disable interrupts, which we can do only from supervisor mode. 51 _Atomic_word 52 __attribute__ ((__unused__)) 53 __exchange_and_add(volatile _Atomic_word* __mem, int __val) throw () 54 { 55 _Atomic_word __result; 56 short __level, __tmpsr; 57 __asm__ __volatile__ ("move%.w %%sr,%0\n\tor%.l %0,%1\n\tmove%.w %1,%%sr" 58 : "=d"(__level), "=d"(__tmpsr) : "1"(0x700)); 59 60 __result = *__mem; 61 *__mem = __result + __val; 62 __asm__ __volatile__ ("move%.w %0,%%sr" : : "d"(__level)); 63 64 return __result; 65 } 66 67 #else 68 69 template<int __inst> 70 struct _Atomicity_lock 71 { 72 static volatile unsigned char _S_atomicity_lock; 73 }; 74 75 template<int __inst> 76 volatile unsigned char _Atomicity_lock<__inst>::_S_atomicity_lock = 0; 77 78 template volatile unsigned char _Atomicity_lock<0>::_S_atomicity_lock; 79 80 _Atomic_word 81 __attribute__ ((__unused__)) 82 __exchange_and_add(volatile _Atomic_word* __mem, int __val) throw () 83 { 84 _Atomic_word __result; 85 86 // bset with no immediate addressing (not SMP-safe) 87 #if defined(__mcfisaa__) || defined(__mcfisaaplus__) 88 __asm__ __volatile__("1: bset.b #7,%0@\n\tjbne 1b" 89 : /* no outputs */ 90 : "a"(&_Atomicity_lock<0>::_S_atomicity_lock) 91 : "cc", "memory"); 92 93 // CPU32 and CF ISAs B & C support test-and-set (SMP-safe). 94 #elif defined(__mcpu32__) || defined(__mcfisab__) || defined (__mcfisac__) 95 __asm__ __volatile__("1: tas %0\n\tjbne 1b" 96 : "+m"(_Atomicity_lock<0>::_S_atomicity_lock) 97 : /* none */ 98 : "cc"); 99 100 // Use bset with immediate addressing for 68000/68010 (not SMP-safe) 101 // NOTE: TAS is available on the 68000, but unsupported by some Amiga 102 // memory controllers. 103 #else 104 __asm__ __volatile__("1: bset.b #7,%0\n\tjbne 1b" 105 : "+m"(_Atomicity_lock<0>::_S_atomicity_lock) 106 : /* none */ 107 : "cc"); 108 #endif 109 110 __result = *__mem; 111 *__mem = __result + __val; 112 113 _Atomicity_lock<0>::_S_atomicity_lock = 0; 114 115 return __result; 116 } 117 118 #endif /* TAS / BSET */ 119 120 void 121 __attribute__ ((__unused__)) 122 __atomic_add(volatile _Atomic_word* __mem, int __val) throw () 123 { 124 // Careful: using add.l with a memory destination is not 125 // architecturally guaranteed to be atomic. 126 __exchange_and_add(__mem, __val); 127 } 128 129 _GLIBCXX_END_NAMESPACE 130