powerpc: Add the lock elision using HTM

This patch adds support for lock elision using ISA 2.07 hardware
transactional memory instructions for pthread_mutex primitives.
Similar to s390 version, the for elision logic defined in
'force-elision.h' is only enabled if ENABLE_LOCK_ELISION is defined.

Also, the lock elision code should be able to be built even with
a compiler that does not provide HTM support with builtins.
However I have noted the performance is sub-optimal due scheduling
pressures.

1 files changed, 32 insertions, 0 deletions

diff --git a/sysdeps/unix/sysv/linux/powerpc/elision-unlock.c b/sysdeps/unix/sysv/linux/powerpc/elision-unlock.c
new file mode 100644
index 0000000000..59d46bb43a
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/powerpc/elision-unlock.c
@@ -0,0 +1,32 @@
+/* elision-unlock.c: Commit an elided pthread lock.
+   Copyright (C) 2014 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include "pthreadP.h"
+#include "lowlevellock.h"
+#include "htm.h"
+
+int
+__lll_unlock_elision(int *lock, int pshared)
+{
+  /* When the lock was free we're in a transaction.  */
+  if (*lock == 0)
+    __builtin_tend (0);
+  else
+    lll_unlock ((*lock), pshared);
+  return 0;
+}