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

   1 // Low-level functions for atomic operations: m68k version -*- C++ -*-
   2
   3 // Copyright (C) 2001-2020 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   // 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