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08c852026d
This patch is the result of running run-clang-tidy -fix -header-filter=.* -checks='-*,modernize-use-equals-default' . Code style changes have been done on top. The result of this change leads to the following improvements: 1. Binary size reduction. * For a -DBUILD_CONFIG=mysql_release build, the binary size is reduced by ~400kb. * A raw -DCMAKE_BUILD_TYPE=Release reduces the binary size by ~1.4kb. 2. Compiler can better understand the intent of the code, thus it leads to more optimization possibilities. Additionally it enabled detecting unused variables that had an empty default constructor but not marked so explicitly. Particular change required following this patch in sql/opt_range.cc result_keys, an unused template class Bitmap now correctly issues unused variable warnings. Setting Bitmap template class constructor to default allows the compiler to identify that there are no side-effects when instantiating the class. Previously the compiler could not issue the warning as it assumed Bitmap class (being a template) would not be performing a NO-OP for its default constructor. This prevented the "unused variable warning".
65 lines
2.8 KiB
C++
65 lines
2.8 KiB
C++
/* Copyright (c) 2020, MariaDB
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA */
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#pragma once
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#ifdef __cplusplus
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#include <atomic>
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/**
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A wrapper for std::atomic, defaulting to std::memory_order_relaxed.
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When it comes to atomic loads or stores at std::memory_order_relaxed
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on IA-32 or AMD64, this wrapper is only introducing some constraints
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to the C++ compiler, to prevent some optimizations of loads or
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stores.
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On POWER and ARM, atomic loads and stores involve different instructions
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from normal loads and stores and will thus incur some overhead.
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Because atomic read-modify-write operations will always incur
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overhead, we intentionally do not define
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operator++(), operator--(), operator+=(), operator-=(), or similar,
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to make the overhead stand out in the users of this code.
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*/
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template <typename Type> class Atomic_relaxed
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{
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std::atomic<Type> m;
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public:
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Atomic_relaxed(const Atomic_relaxed<Type> &rhs)
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{ m.store(rhs, std::memory_order_relaxed); }
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Atomic_relaxed(Type val) : m(val) {}
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Atomic_relaxed() = default;
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operator Type() const { return m.load(std::memory_order_relaxed); }
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Type operator=(const Type val)
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{ m.store(val, std::memory_order_relaxed); return val; }
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Type operator=(const Atomic_relaxed<Type> &rhs) { return *this= Type{rhs}; }
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Type fetch_add(const Type i, std::memory_order o= std::memory_order_relaxed)
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{ return m.fetch_add(i, o); }
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Type fetch_sub(const Type i, std::memory_order o= std::memory_order_relaxed)
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{ return m.fetch_sub(i, o); }
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Type fetch_xor(const Type i, std::memory_order o= std::memory_order_relaxed)
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{ return m.fetch_xor(i, o); }
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Type fetch_and(const Type i, std::memory_order o= std::memory_order_relaxed)
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{ return m.fetch_and(i, o); }
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Type fetch_or(const Type i, std::memory_order o= std::memory_order_relaxed)
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{ return m.fetch_or(i, o); }
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bool compare_exchange_strong(Type& i1, const Type i2,
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std::memory_order o1= std::memory_order_relaxed,
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std::memory_order o2= std::memory_order_relaxed)
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{ return m.compare_exchange_strong(i1, i2, o1, o2); }
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Type exchange(const Type i, std::memory_order o= std::memory_order_relaxed)
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{ return m.exchange(i, o); }
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};
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#endif /* __cplusplus */
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