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, 119 insertions, 0 deletions

diff --git a/REORG.TODO/sysdeps/x86/elide.h b/REORG.TODO/sysdeps/x86/elide.h
new file mode 100644
index 0000000000..53de41836e
--- /dev/null
+++ b/REORG.TODO/sysdeps/x86/elide.h
@@ -0,0 +1,119 @@
+/* elide.h: Generic lock elision support.
+   Copyright (C) 2014-2017 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_H
+#define ELIDE_H 1
+
+#include <hle.h>
+#include <elision-conf.h>
+#include <atomic.h>
+
+
+/* Adapt elision with ADAPT_COUNT and STATUS and decide retries.  */
+
+static inline bool
+elision_adapt(signed char *adapt_count, unsigned int status)
+{
+  if (status & _XABORT_RETRY)
+    return false;
+  if ((status & _XABORT_EXPLICIT)
+      && _XABORT_CODE (status) == _ABORT_LOCK_BUSY)
+    {
+      /* Right now we skip here.  Better would be to wait a bit
+	 and retry.  This likely needs some spinning. Be careful
+	 to avoid writing the lock.
+	 Using relaxed MO and separate atomic accesses is sufficient because
+	 adapt_count is just a hint.  */
+      if (atomic_load_relaxed (adapt_count) != __elision_aconf.skip_lock_busy)
+	atomic_store_relaxed (adapt_count, __elision_aconf.skip_lock_busy);
+    }
+  /* Internal abort.  There is no chance for retry.
+     Use the normal locking and next time use lock.
+     Be careful to avoid writing to the lock.  See above for MO.  */
+  else if (atomic_load_relaxed (adapt_count)
+      != __elision_aconf.skip_lock_internal_abort)
+    atomic_store_relaxed (adapt_count,
+	__elision_aconf.skip_lock_internal_abort);
+  return true;
+}
+
+/* is_lock_free must be executed inside the transaction */
+
+/* Returns true if lock defined by IS_LOCK_FREE was elided.
+   ADAPT_COUNT is a per-lock state variable; it must be accessed atomically
+   to avoid data races but is just a hint, so using relaxed MO and separate
+   atomic loads and stores instead of atomic read-modify-write operations is
+   sufficient.  */
+
+#define ELIDE_LOCK(adapt_count, is_lock_free)			\
+  ({								\
+    int ret = 0;						\
+								\
+    if (atomic_load_relaxed (&(adapt_count)) <= 0)		\
+      {								\
+        for (int i = __elision_aconf.retry_try_xbegin; i > 0; i--) \
+          {							\
+            unsigned int status;				\
+	    if ((status = _xbegin ()) == _XBEGIN_STARTED)	\
+	      {							\
+	        if (is_lock_free)				\
+	          {						\
+		    ret = 1;					\
+		    break;					\
+	          }						\
+	        _xabort (_ABORT_LOCK_BUSY);			\
+	      }							\
+	    if (!elision_adapt (&(adapt_count), status))	\
+	      break;						\
+          }							\
+      }								\
+    else 							\
+      atomic_store_relaxed (&(adapt_count),			\
+	  atomic_load_relaxed (&(adapt_count)) - 1);		\
+    ret;							\
+  })
+
+/* Returns true if lock defined by IS_LOCK_FREE was try-elided.
+   ADAPT_COUNT is a per-lock state variable.  */
+
+#define ELIDE_TRYLOCK(adapt_count, is_lock_free, write) ({	\
+  int ret = 0;						\
+  if (__elision_aconf.retry_try_xbegin > 0)		\
+    {  							\
+      if (write)					\
+        _xabort (_ABORT_NESTED_TRYLOCK);		\
+      ret = ELIDE_LOCK (adapt_count, is_lock_free);     \
+    }							\
+    ret;						\
+    })
+
+/* Returns true if lock defined by IS_LOCK_FREE was elided.  The call
+   to _xend crashes if the application incorrectly tries to unlock a
+   lock which has not been locked.  */
+
+#define ELIDE_UNLOCK(is_lock_free)		\
+  ({						\
+  int ret = 0;					\
+  if (is_lock_free)				\
+    {						\
+      _xend ();					\
+      ret = 1;					\
+    }						\
+  ret;						\
+  })
+
+#endif