nptl: Extract <bits/atomic_wide_counter.h> from pthread_cond_common.c

And make it an installed header.  This addresses a few aliasing
violations (which do not seem to result in miscompilation due to
the use of atomics), and also enables use of wide counters in other
parts of the library.

The debug output in nptl/tst-cond22 has been adjusted to print
the 32-bit values instead because it avoids a big-endian/little-endian
difference.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

1 files changed, 35 insertions, 0 deletions

diff --git a/bits/atomic_wide_counter.h b/bits/atomic_wide_counter.h
new file mode 100644
index 0000000000..0687eb554e
--- /dev/null
+++ b/bits/atomic_wide_counter.h
@@ -0,0 +1,35 @@
+/* Monotonically increasing wide counters (at least 62 bits).
+   Copyright (C) 2016-2021 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
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _BITS_ATOMIC_WIDE_COUNTER_H
+#define _BITS_ATOMIC_WIDE_COUNTER_H
+
+/* Counter that is monotonically increasing (by less than 2**31 per
+   increment), with a single writer, and an arbitrary number of
+   readers.  */
+typedef union
+{
+  __extension__ unsigned long long int __value64;
+  struct
+  {
+    unsigned int __low;
+    unsigned int __high;
+  } __value32;
+} __atomic_wide_counter;
+
+#endif /* _BITS_ATOMIC_WIDE_COUNTER_H */