1 // Low-level functions for atomic operations: m68k version -*- C++ -*- 2 3 // Copyright (C) 2001, 2002, 2003, 2004 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 #include <bits/atomicity.h> 31 32 namespace __gnu_cxx 33 { 34 #if ( defined(__mc68020__) || defined(__mc68030__) \ 35 || defined(__mc68040__) || defined(__mc68060__) ) \ 36 && !defined(__mcpu32__) 37 // These variants support compare-and-swap. 38 _Atomic_word 39 __attribute__ ((__unused__)) __exchange_and_add(volatile _Atomic_word * __mem,int __val)40 __exchange_and_add(volatile _Atomic_word* __mem, int __val) 41 { 42 register _Atomic_word __result = *__mem; 43 register _Atomic_word __temp; 44 __asm__ __volatile__ ("1: move%.l %0,%1\n\t" 45 "add%.l %3,%1\n\t" 46 "cas%.l %0,%1,%2\n\t" 47 "jne 1b" 48 : "=d" (__result), "=&d" (__temp), "=m" (*__mem) 49 : "d" (__val), "0" (__result), "m" (*__mem)); 50 return __result; 51 } 52 53 #elif defined(__rtems__) 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) 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) 88 { 89 _Atomic_word __result; 90 91 // bset with no immediate addressing (not SMP-safe) 92 #if defined(__mcf5200__) || defined(__mcf5300__) 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 MCF5400 support test-and-set (SMP-safe). 99 #elif defined(__mcpu32__) || defined(__mcf5400__) 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__)) __atomic_add(volatile _Atomic_word * __mem,int __val)127 __atomic_add(volatile _Atomic_word* __mem, int __val) 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 } // namespace __gnu_cxx 134