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70 lines
2.2 KiB
C
70 lines
2.2 KiB
C
/* Copyright (C) 2018 Free Software Foundation, Inc.
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Contributed by Andreas Krebbel <krebbel@linux.vnet.ibm.com>
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This file is part of the GNU Atomic Library (libatomic).
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Libatomic is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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Libatomic is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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more details.
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Under Section 7 of GPL version 3, you are granted additional
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permissions described in the GCC Runtime Library Exception, version
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3.1, as published by the Free Software Foundation.
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You should have received a copy of the GNU General Public License and
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a copy of the GCC Runtime Library Exception along with this program;
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see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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<http://www.gnu.org/licenses/>. */
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#include <libatomic_i.h>
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/* The compiler builtin will use the hardware instruction cdsg if the
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memory operand is properly aligned and will fall back to the
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library call otherwise.
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In case the compiler for one part is able to detect that the
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location is aligned and fails to do so for another usage of the hw
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instruction and the sw fall back would be mixed on the same memory
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location. To avoid this the library fall back also has to use the
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hardware instruction if possible. */
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#if !DONE && N == 16
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UTYPE
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SIZE(libat_exchange) (UTYPE *mptr, UTYPE newval, int smodel UNUSED)
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{
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if (!((uintptr_t)mptr & 0xf))
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{
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/* Use the builtin only if the memory operand is 16 byte
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aligned. */
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return __atomic_exchange_n ((UTYPE *)__builtin_assume_aligned (mptr, 16),
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newval, __ATOMIC_SEQ_CST);
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}
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else
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{
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UTYPE oldval;
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UWORD magic;
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pre_seq_barrier (smodel);
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magic = protect_start (mptr);
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oldval = *mptr;
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*mptr = newval;
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protect_end (mptr, magic);
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post_seq_barrier (smodel);
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return oldval;
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}
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}
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#define DONE 1
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#endif /* N == 16 */
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#include "../../exch_n.c"
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