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/* Copyright (C) 2012 Free Software Foundation, Inc.
Contributed by Richard Henderson <rth@redhat.com>.
This file is part of the GNU Atomic Library (libatomic).
Libatomic 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 3 of the License, or
(at your option) any later version.
Libatomic 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.
Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.
You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
<http://www.gnu.org/licenses/>. */
#include "libatomic_i.h"
#define EXACT(N) \
do { \
if (!C2(HAVE_INT,N)) break; \
if ((uintptr_t)ptr & (N - 1)) break; \
if (__atomic_always_lock_free(N, 0)) return true; \
if (C2(MAYBE_HAVE_ATOMIC_CAS_,N)) return true; \
} while (0)
#define LARGER(N) \
do { \
uintptr_t r = (uintptr_t)ptr & (N - 1); \
if (!C2(HAVE_INT,N)) break; \
if (!C2(HAVE_ATOMIC_LDST_,N)) break; \
if (!C2(MAYBE_HAVE_ATOMIC_CAS_,N)) break; \
if (r + n <= N) return true; \
} while (0)
bool
libat_is_lock_free (size_t n, void *ptr)
{
switch (n)
{
case 0: return true;
case 1: EXACT(1); goto L4;
case 2: EXACT(2); goto L4;
case 4: EXACT(4); goto L8;
case 8: EXACT(8); goto L16;
case 16: EXACT(16); break;
case 3: L4: LARGER(4); /* FALLTHRU */
case 5 ... 7: L8: LARGER(8); /* FALLTHRU */
case 9 ... 15: L16: LARGER(16); break;
}
return false;
}
EXPORT_ALIAS (is_lock_free);
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