From 1bc5aee63eb72b341f506ad058502cd0361f0d10 Mon Sep 17 00:00:00 2001
From: Ben Cheng <bccheng@google.com>
Date: Tue, 25 Mar 2014 22:37:19 -0700
Subject: Initial checkin of GCC 4.9.0 from trunk (r208799).

Change-Id: I48a3c08bb98542aa215912a75f03c0890e497dba
---
 gcc-4.9/libatomic/cas_n.c | 124 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 124 insertions(+)
 create mode 100644 gcc-4.9/libatomic/cas_n.c

(limited to 'gcc-4.9/libatomic/cas_n.c')

diff --git a/gcc-4.9/libatomic/cas_n.c b/gcc-4.9/libatomic/cas_n.c
new file mode 100644
index 000000000..801262d55
--- /dev/null
+++ b/gcc-4.9/libatomic/cas_n.c
@@ -0,0 +1,124 @@
+/* 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));
-- 
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