Adding upstream version 1:10.11.6.upstream/1%10.11.6

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 69 insertions, 0 deletions

diff --git a/include/my_atomic_wrapper.h b/include/my_atomic_wrapper.h
new file mode 100644
index 00000000..7b35b14d
--- /dev/null
+++ b/include/my_atomic_wrapper.h
@@ -0,0 +1,69 @@
+/* Copyright (c) 2020, 2021, MariaDB
+
+   This program 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; version 2 of the License.
+
+   This program 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.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335  USA */
+
+#pragma once
+#ifdef __cplusplus
+#include <atomic>
+/**
+  A wrapper for std::atomic, defaulting to std::memory_order_relaxed.
+
+  When it comes to atomic loads or stores at std::memory_order_relaxed
+  on IA-32 or AMD64, this wrapper is only introducing some constraints
+  to the C++ compiler, to prevent some optimizations of loads or
+  stores.
+
+  On POWER and ARM, atomic loads and stores involve different instructions
+  from normal loads and stores and will thus incur some overhead.
+
+  Because atomic read-modify-write operations will always incur
+  overhead, we intentionally do not define
+  operator++(), operator--(), operator+=(), operator-=(), or similar,
+  to make the overhead stand out in the users of this code.
+*/
+template <typename Type> class Atomic_relaxed
+{
+  std::atomic<Type> m;
+public:
+  Atomic_relaxed(const Atomic_relaxed<Type> &rhs)
+  { m.store(rhs, std::memory_order_relaxed); }
+  Atomic_relaxed(Type val) : m(val) {}
+  Atomic_relaxed() = default;
+
+  Type load(std::memory_order o= std::memory_order_relaxed) const
+  { return m.load(o); }
+  void store(Type i, std::memory_order o= std::memory_order_relaxed)
+  { m.store(i, o); }
+  operator Type() const { return m.load(); }
+  Type operator=(const Type i) { store(i); return i; }
+  Type operator=(const Atomic_relaxed<Type> &rhs) { return *this= Type{rhs}; }
+  Type operator+=(const Type i) { return fetch_add(i); }
+  Type fetch_add(const Type i, std::memory_order o= std::memory_order_relaxed)
+  { return m.fetch_add(i, o); }
+  Type fetch_sub(const Type i, std::memory_order o= std::memory_order_relaxed)
+  { return m.fetch_sub(i, o); }
+  Type fetch_xor(const Type i, std::memory_order o= std::memory_order_relaxed)
+  { return m.fetch_xor(i, o); }
+  Type fetch_and(const Type i, std::memory_order o= std::memory_order_relaxed)
+  { return m.fetch_and(i, o); }
+  Type fetch_or(const Type i, std::memory_order o= std::memory_order_relaxed)
+  { return m.fetch_or(i, o); }
+  bool compare_exchange_strong(Type& i1, const Type i2,
+                               std::memory_order o1= std::memory_order_relaxed,
+                               std::memory_order o2= std::memory_order_relaxed)
+  { return m.compare_exchange_strong(i1, i2, o1, o2); }
+  Type exchange(const Type i, std::memory_order o= std::memory_order_relaxed)
+  { return m.exchange(i, o); }
+};
+#endif /* __cplusplus */