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authorBen Cheng <bccheng@google.com>2014-03-25 22:37:19 -0700
committerBen Cheng <bccheng@google.com>2014-03-25 22:37:19 -0700
commit1bc5aee63eb72b341f506ad058502cd0361f0d10 (patch)
treec607e8252f3405424ff15bc2d00aa38dadbb2518 /gcc-4.9/libatomic/cas_n.c
parent283a0bf58fcf333c58a2a92c3ebbc41fb9eb1fdb (diff)
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Initial checkin of GCC 4.9.0 from trunk (r208799).
Change-Id: I48a3c08bb98542aa215912a75f03c0890e497dba
Diffstat (limited to 'gcc-4.9/libatomic/cas_n.c')
-rw-r--r--gcc-4.9/libatomic/cas_n.c124
1 files changed, 124 insertions, 0 deletions
diff --git a/gcc-4.9/libatomic/cas_n.c b/gcc-4.9/libatomic/cas_n.c
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+/* Copyright (C) 2012-2014 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"
+
+
+/* If we support the builtin, just use it. */
+#if !DONE && defined(atomic_compare_exchange_n)
+bool
+SIZE(libat_compare_exchange) (UTYPE *mptr, UTYPE *eptr, UTYPE newval,
+ int smodel, int fmodel UNUSED)
+{
+ if (maybe_specialcase_relaxed(smodel))
+ return atomic_compare_exchange_n (mptr, eptr, newval, false,
+ __ATOMIC_RELAXED, __ATOMIC_RELAXED);
+ else if (maybe_specialcase_acqrel(smodel))
+ return atomic_compare_exchange_n (mptr, eptr, newval, false,
+ __ATOMIC_ACQ_REL, __ATOMIC_RELAXED);
+ else
+ return atomic_compare_exchange_n (mptr, eptr, newval, false,
+ __ATOMIC_SEQ_CST, __ATOMIC_RELAXED);
+}
+
+#define DONE 1
+#endif /* HAVE_ATOMIC_CAS */
+
+
+/* If this type is not larger than word-sized, fall back to a word-sized
+ compare-and-swap loop, possibly assisted by the OS. */
+#if !DONE && N <= WORDSIZE && defined(atomic_compare_exchange_w)
+bool
+SIZE(libat_compare_exchange) (UTYPE *mptr, UTYPE *eptr, UTYPE newval,
+ int smodel, int fmodel)
+{
+ UWORD mask, shift, weval, woldval, wnewval, t, *wptr;
+
+ pre_barrier (smodel);
+
+ if (N < WORDSIZE)
+ {
+ wptr = (UWORD *)((uintptr_t)mptr & -WORDSIZE);
+ shift = (((uintptr_t)mptr % WORDSIZE) * CHAR_BIT) ^ SIZE(INVERT_MASK);
+ mask = SIZE(MASK) << shift;
+ }
+ else
+ {
+ wptr = (UWORD *)mptr;
+ shift = 0;
+ mask = -1;
+ }
+
+ weval = *eptr << shift;
+ wnewval = (UWORD)newval << shift;
+ woldval = __atomic_load_n (wptr, __ATOMIC_RELAXED);
+ do
+ {
+ if ((woldval & mask) != weval)
+ goto failure;
+ t = (woldval & ~mask) | wnewval;
+ }
+ while (!atomic_compare_exchange_w (wptr, &woldval, t, true,
+ __ATOMIC_RELAXED, __ATOMIC_RELAXED));
+ post_barrier (smodel);
+ return true;
+
+ failure:
+ *eptr = woldval >> shift;
+ post_barrier (fmodel);
+ return false;
+}
+
+#define DONE 1
+#endif /* HAVE_ATOMIC_CAS && N <= WORDSIZE */
+
+
+/* Otherwise, fall back to some sort of protection mechanism. */
+#if !DONE
+bool
+SIZE(libat_compare_exchange) (UTYPE *mptr, UTYPE *eptr, UTYPE newval,
+ int smodel, int fmodel UNUSED)
+{
+ UTYPE oldval;
+ UWORD magic;
+ bool ret;
+
+ pre_seq_barrier (smodel);
+ magic = protect_start (mptr);
+
+ oldval = *mptr;
+ ret = (oldval == *eptr);
+ if (ret)
+ *mptr = newval;
+ else
+ *eptr = oldval;
+
+ protect_end (mptr, magic);
+ post_seq_barrier (smodel);
+
+ return ret;
+}
+#endif
+
+EXPORT_ALIAS (SIZE(compare_exchange));