--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libatomic/store_n.c	Fri Oct 27 22:46:09 2017 +0900
@@ -0,0 +1,112 @@
+/* Copyright (C) 2012-2017 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 && SIZE(HAVE_ATOMIC_LDST)
+void
+SIZE(libat_store) (UTYPE *mptr, UTYPE newval, int smodel)
+{
+  if (maybe_specialcase_relaxed(smodel))
+    __atomic_store_n (mptr, newval, __ATOMIC_RELAXED);
+  else if (maybe_specialcase_acqrel(smodel))
+    /* Note that ACQ and ACQ_REL are not valid for store.  */
+    __atomic_store_n (mptr, newval, __ATOMIC_RELEASE);
+  else
+    __atomic_store_n (mptr, newval, __ATOMIC_SEQ_CST);
+}
+
+#define DONE 1
+#endif /* HAVE_ATOMIC_STORE */
+
+/* If we have compare-and-swap, use it perform the store.  */
+#if !DONE && defined(atomic_compare_exchange_n)
+void
+SIZE(libat_store) (UTYPE *mptr, UTYPE newval, int smodel)
+{
+  UTYPE oldval;
+
+  pre_barrier (smodel);
+
+  oldval = *mptr;
+  while (!atomic_compare_exchange_n (mptr, &oldval, newval, true,
+				     __ATOMIC_RELAXED, __ATOMIC_RELAXED))
+    continue;
+
+  post_barrier (smodel);
+}
+
+#define DONE 1
+#endif /* atomic_compare_exchange_n */
+
+
+/* If this type is smaller than word-sized, fall back to a word-sized
+   compare-and-swap loop.  */
+#if !DONE && N < WORDSIZE && defined(atomic_compare_exchange_w)
+void
+SIZE(libat_store) (UTYPE *mptr, UTYPE newval, int smodel)
+{
+  UWORD mask, shift, woldval, wnewval, t, *wptr;
+
+  pre_barrier (smodel);
+
+  wptr = (UWORD *)((uintptr_t)mptr & -WORDSIZE);
+  shift = (((uintptr_t)mptr % WORDSIZE) * CHAR_BIT) ^ SIZE(INVERT_MASK);
+  mask = SIZE(MASK) << shift;
+
+  wnewval = (UWORD)newval << shift;
+  woldval = __atomic_load_n (wptr, __ATOMIC_RELAXED);
+  do
+    {
+      t = (woldval & ~mask) | wnewval;
+    }
+  while (!atomic_compare_exchange_w (wptr, &woldval, t));
+
+  post_barrier (smodel);
+}
+
+#define DONE 1
+#endif /* N < WORDSIZE && atomic_compare_exchange_w */
+
+
+/* Otherwise, fall back to some sort of protection mechanism.  */
+#if !DONE
+void
+SIZE(libat_store) (UTYPE *mptr, UTYPE newval, int smodel)
+{
+  UWORD magic;
+
+  pre_seq_barrier (smodel);
+  magic = protect_start (mptr);
+
+  *mptr = newval;
+
+  protect_end (mptr, magic);
+  post_seq_barrier (smodel);
+}
+#endif
+
+EXPORT_ALIAS (SIZE(store));