accfbd4cb3
The __is_trivially_relocatable builtin has semantics that do not correspond to any current or future notion of trivial relocation. Furthermore, it currently leads to incorrect optimizations for some types on supported compilers: - Clang on Windows where types with non-trivial destructors get incorrectly optimized - AppleClang where types with non-trivial move constructors get incorrectly optimized Until there is an agreed upon and bugfree implementation of what it means to be trivially relocatable, it is safer to simply use trivially copyable instead. This doesn't leave a lot of types behind and is definitely correct.
72 lines
2.4 KiB
C++
72 lines
2.4 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// <vector>
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// Make sure we don't miscompile vector operations for types that shouldn't be considered
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// trivially relocatable.
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#include <vector>
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#include <cassert>
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#include <cstddef>
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#include <type_traits>
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#include <utility>
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#include "test_macros.h"
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struct Tracker {
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std::size_t move_constructs = 0;
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};
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struct [[clang::trivial_abi]] Inner {
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TEST_CONSTEXPR_CXX20 explicit Inner(Tracker* tracker) : tracker_(tracker) {}
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TEST_CONSTEXPR_CXX20 Inner(const Inner& rhs) : tracker_(rhs.tracker_) { tracker_->move_constructs += 1; }
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TEST_CONSTEXPR_CXX20 Inner(Inner&& rhs) : tracker_(rhs.tracker_) { tracker_->move_constructs += 1; }
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Tracker* tracker_;
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};
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// Even though this type contains a trivial_abi type, it is not trivially move-constructible,
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// so we should not attempt to optimize its move construction + destroy using trivial relocation.
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struct NotTriviallyMovable {
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TEST_CONSTEXPR_CXX20 explicit NotTriviallyMovable(Tracker* tracker) : inner_(tracker) {}
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TEST_CONSTEXPR_CXX20 NotTriviallyMovable(NotTriviallyMovable&& other) : inner_(std::move(other.inner_)) {}
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Inner inner_;
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};
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static_assert(!std::is_trivially_copyable<NotTriviallyMovable>::value, "");
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LIBCPP_STATIC_ASSERT(!std::__libcpp_is_trivially_relocatable<NotTriviallyMovable>::value, "");
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TEST_CONSTEXPR_CXX20 bool tests() {
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Tracker track;
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std::vector<NotTriviallyMovable> v;
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// Fill the vector at its capacity, such that any subsequent push_back would require growing.
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v.reserve(5);
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std::size_t const capacity = v.capacity(); // could technically be more than 5
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while (v.size() < v.capacity()) {
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v.emplace_back(&track);
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}
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assert(track.move_constructs == 0);
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assert(v.capacity() == capacity);
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assert(v.size() == capacity);
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// Force a reallocation of the buffer + relocalization of the elements.
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// All the existing elements of the vector should be move-constructed to their new location.
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v.emplace_back(&track);
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assert(track.move_constructs == capacity);
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return true;
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}
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int main(int, char**) {
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tests();
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#if TEST_STD_VER >= 20
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static_assert(tests());
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#endif
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return 0;
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}
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