--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libatomic/glfree.c	Fri Oct 27 22:46:09 2017 +0900
@@ -0,0 +1,82 @@
+/* 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"
+
+/* Accesses with a power-of-two size are not lock-free if we don't have an
+   integer type of this size or if they are not naturally aligned.  They
+   are lock-free if such a naturally aligned access is always lock-free
+   according to the compiler, which requires that both atomic loads and CAS
+   are available.
+   In all other cases, we fall through to LARGER (see below).  */
+#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)) break;			\
+    if (C2(FAST_ATOMIC_LDST_,N)) return true;			\
+  } while (0)
+
+
+/* We next check to see if an access of a larger size is lock-free.  We use
+   a similar check as in EXACT, except that we also check that the alignment
+   of the access is so that the data to be accessed is completely covered
+   by the larger access.  */
+#define LARGER(N)						\
+  do {								\
+    uintptr_t r = (uintptr_t)ptr & (N - 1);			\
+    if (!C2(HAVE_INT,N)) break;					\
+    if (!C2(FAST_ATOMIC_LDST_,N)) break;			\
+    if (!C2(MAYBE_HAVE_ATOMIC_CAS_,N)) break;			\
+    if (r + n <= N) return true;				\
+  } while (0)
+
+
+/* Note that this can return that a size/alignment is not lock-free even if
+   all the operations that we use to implement the respective accesses provide
+   lock-free forward progress as specified in C++14:  Users likely expect
+   "lock-free" to also mean "fast", which is why we do not return true if, for
+   example, we implement loads with this size/alignment using a CAS.  */
+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);