Prepare for radical source tree reorganization.zack/build-layout-experiment

All top-level files and directories are moved into a temporary storage
directory, REORG.TODO, except for files that will certainly still
exist in their current form at top level when we're done (COPYING,
COPYING.LIB, LICENSES, NEWS, README), all old ChangeLog files (which
are moved to the new directory OldChangeLogs, instead), and the
generated file INSTALL (which is just deleted; in the new order, there
will be no generated files checked into version control).

1 files changed, 125 insertions, 0 deletions

diff --git a/REORG.TODO/sysdeps/powerpc/nptl/elide.h b/REORG.TODO/sysdeps/powerpc/nptl/elide.h
new file mode 100644
index 0000000000..1c42814b71
--- /dev/null
+++ b/REORG.TODO/sysdeps/powerpc/nptl/elide.h
@@ -0,0 +1,125 @@
+/* elide.h: Generic lock elision support for powerpc.
+   Copyright (C) 2015-2017 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/>.  */
+
+#ifndef ELIDE_PPC_H
+# define ELIDE_PPC_H
+
+#ifdef ENABLE_LOCK_ELISION
+# include <htm.h>
+# include <elision-conf.h>
+
+/* Get the new value of adapt_count according to the elision
+   configurations.  Returns true if the system should retry again or false
+   otherwise.  */
+static inline bool
+__get_new_count (uint8_t *adapt_count, int attempt)
+{
+  /* A persistent failure indicates that a retry will probably
+     result in another failure.  Use normal locking now and
+     for the next couple of calls.  */
+  if (_TEXASRU_FAILURE_PERSISTENT (__builtin_get_texasru ()))
+    {
+      if (__elision_aconf.skip_lock_internal_abort > 0)
+	*adapt_count = __elision_aconf.skip_lock_internal_abort;
+      return false;
+    }
+  /* Same logic as above, but for a number of temporary failures in a
+     a row.  */
+  else if (attempt <= 1 && __elision_aconf.skip_lock_out_of_tbegin_retries > 0
+	   && __elision_aconf.try_tbegin > 0)
+    *adapt_count = __elision_aconf.skip_lock_out_of_tbegin_retries;
+  return true;
+}
+
+/* CONCURRENCY NOTES:
+
+   The evaluation of the macro expression is_lock_free encompasses one or
+   more loads from memory locations that are concurrently modified by other
+   threads.  For lock elision to work, this evaluation and the rest of the
+   critical section protected by the lock must be atomic because an
+   execution with lock elision must be equivalent to an execution in which
+   the lock would have been actually acquired and released.  Therefore, we
+   evaluate is_lock_free inside of the transaction that represents the
+   critical section for which we want to use lock elision, which ensures
+   the atomicity that we require.  */
+
+/* Returns 0 if the lock defined by is_lock_free was elided.
+   ADAPT_COUNT is a per-lock state variable.  */
+# define ELIDE_LOCK(adapt_count, is_lock_free)				\
+  ({									\
+    int ret = 0;							\
+    if (adapt_count > 0)						\
+      (adapt_count)--;							\
+    else								\
+      for (int i = __elision_aconf.try_tbegin; i > 0; i--)		\
+	{								\
+	  if (__libc_tbegin (0))					\
+	    {								\
+	      if (is_lock_free)						\
+		{							\
+		  ret = 1;						\
+		  break;						\
+		}							\
+	      __libc_tabort (_ABORT_LOCK_BUSY);				\
+	    }								\
+	  else								\
+	    if (!__get_new_count (&adapt_count,i))			\
+	      break;							\
+	}								\
+    ret;								\
+  })
+
+# define ELIDE_TRYLOCK(adapt_count, is_lock_free, write)	\
+  ({								\
+    int ret = 0;						\
+    if (__elision_aconf.try_tbegin > 0)				\
+      {								\
+	if (write)						\
+	  __libc_tabort (_ABORT_NESTED_TRYLOCK);		\
+	ret = ELIDE_LOCK (adapt_count, is_lock_free);		\
+      }								\
+    ret;							\
+  })
+
+
+static inline bool
+__elide_unlock (int is_lock_free)
+{
+  if (is_lock_free)
+    {
+      /* This code is expected to crash when trying to unlock a lock not
+	 held by this thread.  More information is available in the
+	 __pthread_rwlock_unlock() implementation.  */
+      __libc_tend (0);
+      return true;
+    }
+  return false;
+}
+
+# define ELIDE_UNLOCK(is_lock_free) \
+  __elide_unlock (is_lock_free)
+
+# else
+
+# define ELIDE_LOCK(adapt_count, is_lock_free) 0
+# define ELIDE_TRYLOCK(adapt_count, is_lock_free, write) 0
+# define ELIDE_UNLOCK(is_lock_free) 0
+
+#endif /* ENABLE_LOCK_ELISION  */
+
+#endif