2017-10-07 00:16:47 +00:00
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/* Copyright (C) 2012-2017 Free Software Foundation, Inc.
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2014-09-21 17:33:12 +00:00
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Contributed by Richard Henderson <rth@redhat.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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/* If we natively support the load, and if we're unconcerned with extra
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barriers (e.g. fully in-order cpu for which barriers are a nop), then
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go ahead and expand the operation inline. */
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#if !defined(WANT_SPECIALCASE_RELAXED) && !defined(__OPTIMIZE_SIZE__)
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# define EXACT_INLINE(N, DEST, SRC, DONE) \
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if (C2(HAVE_ATOMIC_LDST_,N)) \
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{ \
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DEST = __atomic_load_n (SRC, __ATOMIC_SEQ_CST); \
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DONE; \
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}
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#else
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# define EXACT_INLINE(N, DEST, SRC, DONE)
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#endif
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#define EXACT_(N, DEST, SRC, DONE) \
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do { \
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EXACT_INLINE (N, DEST, SRC, DONE); \
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DEST = C3(local_,load_,N) (SRC, smodel); \
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DONE; \
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} while (0)
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#define EXACT(N) \
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do { \
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if (!C2(HAVE_INT,N)) break; \
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if ((uintptr_t)mptr & (N - 1)) break; \
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EXACT_(N, *PTR(N,rptr), PTR(N,mptr), return); \
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} while (0)
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#define LARGER(N) \
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do { \
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if (!C2(HAVE_INT,N)) break; \
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r = (uintptr_t)mptr & (N - 1); \
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a = (uintptr_t)mptr & -N; \
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if (r + n <= N) \
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EXACT_ (N, u.C2(i,N), PTR(N,a), goto Lfinish); \
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} while (0)
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void
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libat_load (size_t n, void *mptr, void *rptr, int smodel)
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{
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union max_size_u u;
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uintptr_t r, a;
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switch (n)
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{
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case 0: return;
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case 1: EXACT(1); goto L4;
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case 2: EXACT(2); goto L4;
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case 4: EXACT(4); goto L8;
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case 8: EXACT(8); goto L16;
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case 16: EXACT(16); break;
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case 3: L4: LARGER(4); /* FALLTHRU */
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case 5 ... 7: L8: LARGER(8); /* FALLTHRU */
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case 9 ... 15: L16: LARGER(16); break;
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Lfinish:
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memcpy (rptr, u.b + r, n);
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return;
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}
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pre_seq_barrier (smodel);
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libat_lock_n (mptr, n);
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memcpy (rptr, mptr, n);
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libat_unlock_n (mptr, n);
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post_seq_barrier (smodel);
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}
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EXPORT_ALIAS (load);
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