78 lines
2.4 KiB
C++
78 lines
2.4 KiB
C++
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//===----------------------------------------------------------------------===//
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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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#include <cassert>
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#include <cstddef>
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#include <utility>
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#include "benchmark/benchmark.h"
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template <std::size_t Indx, std::size_t Depth>
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struct C : public virtual C<Indx, Depth - 1>, public virtual C<Indx + 1, Depth - 1> {
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virtual ~C() {}
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};
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template <std::size_t Indx>
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struct C<Indx, 0> {
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virtual ~C() {}
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};
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template <std::size_t Indx, std::size_t Depth>
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struct B : public virtual C<Indx, Depth - 1>, public virtual C<Indx + 1, Depth - 1> {};
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template <class Indx, std::size_t Depth>
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struct makeB;
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template <std::size_t... Indx, std::size_t Depth>
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struct makeB<std::index_sequence<Indx...>, Depth> : public B<Indx, Depth>... {};
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template <std::size_t Width, std::size_t Depth>
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struct A : public makeB<std::make_index_sequence<Width>, Depth> {};
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constexpr std::size_t Width = 10;
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constexpr std::size_t Depth = 5;
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template <typename Destination>
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void CastTo(benchmark::State& state) {
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A<Width, Depth> a;
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auto base = static_cast<C<Width / 2, 0>*>(&a);
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Destination* b = nullptr;
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for (auto _ : state) {
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b = dynamic_cast<Destination*>(base);
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benchmark::DoNotOptimize(b);
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}
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assert(b != 0);
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}
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BENCHMARK(CastTo<B<Width / 2, Depth>>);
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BENCHMARK(CastTo<A<Width, Depth>>);
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BENCHMARK_MAIN();
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/**
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* Benchmark results: (release builds)
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*
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* libcxxabi:
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* ----------------------------------------------------------------------
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* Benchmark Time CPU Iterations
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* ----------------------------------------------------------------------
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* CastTo<B<Width / 2, Depth>> 1997 ns 1997 ns 349247
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* CastTo<A<Width, Depth>> 256 ns 256 ns 2733871
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*
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* libsupc++:
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* ----------------------------------------------------------------------
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* Benchmark Time CPU Iterations
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* ----------------------------------------------------------------------
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* CastTo<B<Width / 2, Depth>> 5240 ns 5240 ns 133091
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* CastTo<A<Width, Depth>> 866 ns 866 ns 808600
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*
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*
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*/
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