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// Low-level functions for atomic operations: m68k version -*- C++ -*-

// Copyright (C) 2001, 2002, 2003, 2004 Free Software Foundation, Inc.

//

// This file is part of the GNU ISO C++ Library.  This library is free

// software; you can redistribute it and/or modify it under the

// terms of the GNU General Public License as published by the

// Free Software Foundation; either version 2, or (at your option)

// any later version.

// This library is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License along

// with this library; see the file COPYING.  If not, write to the Free

// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,

// USA.

// As a special exception, you may use this file as part of a free software

// library without restriction.  Specifically, if other files instantiate

// templates or use macros or inline functions from this file, or you compile

// this file and link it with other files to produce an executable, this

// file does not by itself cause the resulting executable to be covered by

// the GNU General Public License.  This exception does not however

// invalidate any other reasons why the executable file might be covered by

// the GNU General Public License.

#include <bits/atomicity.h>

namespace __gnu_cxx

{

#if ( defined(__mc68020__) || defined(__mc68030__) \

      || defined(__mc68040__) || defined(__mc68060__) ) \

    && !defined(__mcpu32__)

  // These variants support compare-and-swap.

  _Atomic_word

  __attribute__ ((__unused__))

  __exchange_and_add(volatile _Atomic_word* __mem, int __val)

  {

    register _Atomic_word __result = *__mem;

    register _Atomic_word __temp;

    __asm__ __volatile__ ("1: move%.l %0,%1\n\t"

                          "add%.l %3,%1\n\t"

                          "cas%.l %0,%1,%2\n\t"

                          "jne 1b"

                          : "=d" (__result), "=&d" (__temp), "=m" (*__mem)

                          : "d" (__val), "0" (__result), "m" (*__mem));

    return __result;

  }

#elif defined(__rtems__)

  // TAS/JBNE is unsafe on systems with strict priority-based scheduling.

  // Disable interrupts, which we can do only from supervisor mode.

  _Atomic_word

  __attribute__ ((__unused__))

  __exchange_and_add(volatile _Atomic_word* __mem, int __val)

  {

    _Atomic_word __result;

    short __level, __tmpsr;

    __asm__ __volatile__ ("move%.w %%sr,%0\n\tor%.l %0,%1\n\tmove%.w %1,%%sr"

                          : "=d"(__level), "=d"(__tmpsr) : "1"(0x700));

    __result = *__mem;

    *__mem = __result + __val;

    __asm__ __volatile__ ("move%.w %0,%%sr" : : "d"(__level));

    return __result;

  }

#else

  template<int __inst>

    struct _Atomicity_lock

    {

      static volatile unsigned char _S_atomicity_lock;

    };

  template<int __inst>

  volatile unsigned char _Atomicity_lock<__inst>::_S_atomicity_lock = 0;

  template volatile unsigned char _Atomicity_lock<0>::_S_atomicity_lock;

  _Atomic_word

  __attribute__ ((__unused__))

  __exchange_and_add(volatile _Atomic_word* __mem, int __val)

  {

    _Atomic_word __result;

    // bset with no immediate addressing (not SMP-safe)

#if defined(__mcf5200__) || defined(__mcf5300__)

    __asm__ __volatile__("1: bset.b #7,%0@\n\tjbne 1b"

                         : /* no outputs */

                         : "a"(&_Atomicity_lock<0>::_S_atomicity_lock)

                         : "cc", "memory");

    // CPU32 and MCF5400 support test-and-set (SMP-safe).

#elif defined(__mcpu32__) || defined(__mcf5400__)

    __asm__ __volatile__("1: tas %0\n\tjbne 1b"

                         : "+m"(_Atomicity_lock<0>::_S_atomicity_lock)

                         : /* none */

                         : "cc");

    // Use bset with immediate addressing for 68000/68010 (not SMP-safe)

    // NOTE: TAS is available on the 68000, but unsupported by some Amiga

    // memory controllers.

#else

    __asm__ __volatile__("1: bset.b #7,%0\n\tjbne 1b"

                         : "+m"(_Atomicity_lock<0>::_S_atomicity_lock)

                         : /* none */

                         : "cc");

#endif

    __result = *__mem;

    *__mem = __result + __val;

    _Atomicity_lock<0>::_S_atomicity_lock = 0;

    return __result;

  }

#endif /* TAS / BSET */

  void

  __attribute__ ((__unused__))

  __atomic_add(volatile _Atomic_word* __mem, int __val)

  {

    // Careful: using add.l with a memory destination is not

    // architecturally guaranteed to be atomic.

    __exchange_and_add(__mem, __val);

  }

} // namespace __gnu_cxx