This is part of work in progress getting locking back into shape on
powerpc.  (If we ever were in shape, which is doubtful.)  Using the
ia64 version means we have a needless sync at the start of
gomp_mutex_lock (courtesy of __sync_val_compare_and_swap) and a
needless isync at the end of gomp_mutex_unlock (slightly odd use
of __sync_lock_test_and_set to release a lock).  It would be nice to
get rid of the __sync_val_compare_and_swap in config/linux/mutex.c
too.

        * config/linux/powerpc/mutex.h: Rewrite.

Index: libgomp/config/linux/powerpc/mutex.h
===================================================================
--- libgomp/config/linux/powerpc/mutex.h        (revision 181425)
+++ libgomp/config/linux/powerpc/mutex.h        (working copy)
@@ -1,2 +1,75 @@
-/* On PowerPC __sync_lock_test_and_set isn't a full barrier.  */
-#include "config/linux/ia64/mutex.h"
+/* Copyright (C) 2011 Free Software Foundation, Inc.
+   Contributed by Alan Modra <amo...@au1.ibm.com>
+
+   This file is part of the GNU OpenMP Library (libgomp).
+
+   Libgomp 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, or (at your option)
+   any later version.
+
+   Libgomp 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/>.  */
+
+/* This is a Linux specific implementation of a mutex synchronization
+   mechanism for libgomp.  This type is private to the library.  This
+   implementation uses atomic instructions and the futex syscall.  */
+
+#ifndef GOMP_MUTEX_H
+#define GOMP_MUTEX_H 1
+
+typedef int gomp_mutex_t;
+extern void gomp_mutex_lock_slow (gomp_mutex_t *mutex, int);
+extern void gomp_mutex_unlock_slow (gomp_mutex_t *mutex);
+
+#define GOMP_MUTEX_INIT_0 1
+
+enum memmodel
+{
+  MEMMODEL_RELAXED = 0,
+  MEMMODEL_CONSUME = 1,
+  MEMMODEL_ACQUIRE = 2,
+  MEMMODEL_RELEASE = 3,
+  MEMMODEL_ACQ_REL = 4,
+  MEMMODEL_SEQ_CST = 5,
+  MEMMODEL_LAST = 6
+};
+
+static inline void gomp_mutex_init (gomp_mutex_t *mutex)
+{
+  *mutex = 0;
+}
+
+static inline void gomp_mutex_destroy (gomp_mutex_t *mutex)
+{
+}
+
+static inline void gomp_mutex_lock (gomp_mutex_t *mutex)
+{
+  int oldval = 0;
+
+  __atomic_compare_exchange_4 (mutex, &oldval, 1, false,
+                              MEMMODEL_ACQUIRE, MEMMODEL_RELAXED);
+  if (__builtin_expect (oldval != 0, 0))
+    gomp_mutex_lock_slow (mutex, oldval);
+}
+
+static inline void gomp_mutex_unlock (gomp_mutex_t *mutex)
+{
+  int oldval = __atomic_exchange_4 (mutex, 0, MEMMODEL_RELEASE);
+
+  if (__builtin_expect (oldval > 1, 0))
+    gomp_mutex_unlock_slow (mutex);
+}
+#endif /* GOMP_MUTEX_H */

-- 
Alan Modra
Australia Development Lab, IBM

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