libstdc++-v3/config/cpu/m68k/atomicity.h

   1 // Low-level functions for atomic operations: m68k version -*- C++ -*-
   2
   3 // Copyright (C) 2001, 2002 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 #ifndef _GLIBCXX_ATOMICITY_H
  31 #define _GLIBCXX_ATOMICITY_H    1
  32
  33 typedef int _Atomic_word;
  34
  35 #if defined(__mc68020__) || defined(__mc68030__) \
  36     || defined(__mc68040__) || defined(__mc68060__)
  37 // These variants support compare-and-swap.
  38
  39 static inline _Atomic_word
  40 __attribute__ ((__unused__))
  41 __exchange_and_add (volatile _Atomic_word *__mem, int __val)
  42 {
  43   register _Atomic_word __result = *__mem;
  44   register _Atomic_word __temp;
  45   __asm__ __volatile__ ("1: move%.l %0,%1\n\t"
  46                         "add%.l %3,%1\n\t"
  47                         "cas%.l %0,%1,%2\n\t"
  48                         "jne 1b"
  49                         : "=d" (__result), "=&d" (__temp), "+m" (*__mem)
  50                         : "d" (__val), "0" (__result)
  51                         : "memory");
  52   return __result;
  53 }
  54
  55 #elif defined(__rtems__)
  56   /*
  57    * TAS/JBNE is unsafe on systems with strict priority-based scheduling.
  58    * Disable interrupts, which we can do only from supervisor mode.
  59    */
  60 static inline _Atomic_word
  61 __attribute__ ((__unused__))
  62 __exchange_and_add (volatile _Atomic_word *__mem, int __val)
  63 {
  64   _Atomic_word __result;
  65   short __level, __tmpsr;
  66   __asm__ __volatile__ ("move%.w %%sr,%0\n\tor%.l %0,%1\n\tmove%.w %1,%%sr"
  67                        : "=d"(__level), "=d"(__tmpsr) : "1"(0x700));
  68
  69   __result = *__mem;
  70   *__mem = __result + __val;
  71
  72   __asm__ __volatile__ ("move%.w %0,%%sr" : : "d"(__level));
  73
  74   return __result;
  75 }
  76
  77 #elif !defined(__mcf5200__) && !defined(__mcf5300__)
  78 // 68000, 68010, cpu32 and 5400 support test-and-set.
  79
  80 template <int __inst>
  81 struct __Atomicity_lock
  82 {
  83   static volatile unsigned char _S_atomicity_lock;
  84 };
  85
  86 template <int __inst>
  87 volatile unsigned char __Atomicity_lock<__inst>::_S_atomicity_lock = 0;
  88
  89 template volatile unsigned char __Atomicity_lock<0>::_S_atomicity_lock;
  90
  91 static inline _Atomic_word
  92 __attribute__ ((__unused__))
  93 __exchange_and_add (volatile _Atomic_word *__mem, int __val)
  94 {
  95   _Atomic_word __result;
  96
  97   __asm__ __volatile__("1: tas %0\n\tjbne 1b"
  98                        : "=m"(__Atomicity_lock<0>::_S_atomicity_lock)
  99                        : "m"(__Atomicity_lock<0>::_S_atomicity_lock));
 100
 101   __result = *__mem;
 102   *__mem = __result + __val;
 103
 104   __Atomicity_lock<0>::_S_atomicity_lock = 0;
 105
 106   return __result;
 107 }
 108
 109 #elif defined(__vxWorks__) || defined(__embedded__)
 110 // The best we can hope for is to disable interrupts, which we
 111 // can only do from supervisor mode.
 112
 113 static inline _Atomic_word
 114 __attribute__ ((__unused__))
 115 __exchange_and_add (volatile _Atomic_word *__mem, int __val)
 116 {
 117   _Atomic_word __result;
 118   short __level, __tmpsr;
 119   __asm__ __volatile__ ("move%.w %%sr,%0\n\tor%.l %0,%1\n\tmove%.w %1,%%sr"
 120                         : "=d"(__level), "=d"(__tmpsr) : "1"(0x700));
 121
 122   __result = *__mem;
 123   *__mem = __result + __val;
 124
 125   __asm__ __volatile__ ("move%.w %0,%%sr" : : "d"(__level));
 126
 127   return __result;
 128 }
 129
 130 #else
 131 // These variants do not support any atomic operations at all.
 132
 133 #warning "__exchange_and_add is not atomic for this target"
 134
 135 static inline _Atomic_word
 136 __attribute__ ((__unused__))
 137 __exchange_and_add (volatile _Atomic_word *__mem, int __val)
 138 {
 139   _Atomic_word __result;
 140
 141   __result = *__mem;
 142   *__mem = __result + __val;
 143
 144   return __result;
 145 }
 146
 147 #endif /* CAS / IRQ / TAS */
 148
 149 static inline void
 150 __attribute__ ((__unused__))
 151 __atomic_add (volatile _Atomic_word* __mem, int __val)
 152 {
 153   // Careful: using add.l with a memory destination is not
 154   // architecturally guaranteed to be atomic.
 155   (void) __exchange_and_add (__mem, __val);
 156 }
 157
 158 #endif /* atomicity.h */