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2001-02-14 Joel Sherrill <joel@OARcorp.com> * config/cpu/m68k/bits/atomicity.h: Corrected for RTEMS targets which do not have a CAS instruction. From-SVN: r49772
159 lines
4.7 KiB
C++
159 lines
4.7 KiB
C++
// Low-level functions for atomic operations: m68k version -*- C++ -*-
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// Copyright (C) 2001, 2002 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 2, or (at your option)
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// any later version.
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License along
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// with this library; see the file COPYING. If not, write to the Free
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// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
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// USA.
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// As a special exception, you may use this file as part of a free software
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// library without restriction. Specifically, if other files instantiate
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// templates or use macros or inline functions from this file, or you compile
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// this file and link it with other files to produce an executable, this
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// file does not by itself cause the resulting executable to be covered by
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// the GNU General Public License. This exception does not however
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// invalidate any other reasons why the executable file might be covered by
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// the GNU General Public License.
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#ifndef _BITS_ATOMICITY_H
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#define _BITS_ATOMICITY_H 1
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typedef int _Atomic_word;
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#if defined(__mc68020__) || defined(__mc68030__) \
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|| defined(__mc68040__) || defined(__mc68060__)
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// These variants support compare-and-swap.
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static inline _Atomic_word
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__attribute__ ((__unused__))
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__exchange_and_add (volatile _Atomic_word *__mem, int __val)
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{
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register _Atomic_word __result = *__mem;
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register _Atomic_word __temp;
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__asm__ __volatile__ ("1: move%.l %0,%1\n\t"
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"add%.l %2,%1\n\t"
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"cas%.l %0,%1,%3\n\t"
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"jbne 1b"
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: "=d" (__result), "=&d" (__temp)
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: "d" (__val), "m" (*__mem), "0" (__result)
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: "memory");
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return __result;
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}
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#elif defined(__rtems__)
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/*
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* TAS/JBNE is unsafe on systems with strict priority-based scheduling.
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* Disable interrupts, which we can do only from supervisor mode.
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*/
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static inline _Atomic_word
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__attribute__ ((__unused__))
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__exchange_and_add (volatile _Atomic_word *__mem, int __val)
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{
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_Atomic_word __result;
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short __level, __tmpsr;
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__asm__ __volatile__ ("move%.w %%sr,%0\n\tor%.l %0,%1\n\tmove%.w %1,%%sr"
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: "=d"(__level), "=d"(__tmpsr) : "1"(0x700));
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__result = *__mem;
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*__mem = __result + __val;
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__asm__ __volatile__ ("move%.w %0,%%sr" : : "d"(__level));
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return __result;
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}
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#elif !defined(__mcf5200__) && !defined(__mcf5300__)
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// 68000, 68010, cpu32 and 5400 support test-and-set.
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template <int __inst>
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struct __Atomicity_lock
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{
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static volatile unsigned char _S_atomicity_lock;
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};
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template <int __inst>
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volatile unsigned char __Atomicity_lock<__inst>::_S_atomicity_lock = 0;
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template volatile unsigned char __Atomicity_lock<0>::_S_atomicity_lock;
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static inline _Atomic_word
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__attribute__ ((__unused__))
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__exchange_and_add (volatile _Atomic_word *__mem, int __val)
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{
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_Atomic_word __result;
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__asm__ __volatile__("1: tas %0\n\tjbne 1b"
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: "=m"(__Atomicity_lock<0>::_S_atomicity_lock)
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: "m"(__Atomicity_lock<0>::_S_atomicity_lock));
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__result = *__mem;
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*__mem = __result + __val;
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__Atomicity_lock<0>::_S_atomicity_lock = 0;
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return __result;
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}
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#elif defined(__vxWorks__) || defined(__embedded__)
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// The best we can hope for is to disable interrupts, which we
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// can only do from supervisor mode.
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static inline _Atomic_word
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__attribute__ ((__unused__))
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__exchange_and_add (volatile _Atomic_word *__mem, int __val)
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{
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_Atomic_word __result;
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short __level, __tmpsr;
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__asm__ __volatile__ ("move%.w %%sr,%0\n\tor%.l %0,%1\n\tmove%.w %1,%%sr"
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: "=d"(__level), "=d"(__tmpsr) : "1"(0x700));
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__result = *__mem;
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*__mem = __result + __val;
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__asm__ __volatile__ ("move%.w %0,%%sr" : : "d"(__level));
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return __result;
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}
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#else
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// These variants do not support any atomic operations at all.
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#warning "__exchange_and_add is not atomic for this target"
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static inline _Atomic_word
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__attribute__ ((__unused__))
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__exchange_and_add (volatile _Atomic_word *__mem, int __val)
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{
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_Atomic_word __result;
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__result = *__mem;
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*__mem = __result + __val;
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return __result;
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}
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#endif /* CAS / IRQ / TAS */
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static inline void
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__attribute__ ((__unused__))
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__atomic_add (volatile _Atomic_word* __mem, int __val)
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{
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// Careful: using add.l with a memory destination is not
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// architecturally guaranteed to be atomic.
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(void) __exchange_and_add (__mem, __val);
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}
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#endif /* atomicity.h */
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