libcxx/benchmarks/VariantBenchmarks.h

   1 // -*- C++ -*-
   2 //===----------------------------------------------------------------------===//
   3 //
   4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   5 // See https://llvm.org/LICENSE.txt for license information.
   6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #ifndef BENCHMARK_VARIANT_BENCHMARKS_H
  11 #define BENCHMARK_VARIANT_BENCHMARKS_H
  12
  13 #include <array>
  14 #include <cstddef>
  15 #include <tuple>
  16 #include <type_traits>
  17 #include <variant>
  18
  19 #include "benchmark/benchmark.h"
  20
  21 #include "GenerateInput.h"
  22
  23 namespace VariantBenchmarks {
  24
  25 template <std::size_t I>
  26 struct S {
  27   static constexpr size_t v = I;
  28 };
  29
  30 template <std::size_t N, std::size_t... Is>
  31 static auto genVariants(std::index_sequence<Is...>) {
  32   using V                 = std::variant<S<Is>...>;
  33   using F                 = V (*)();
  34   static constexpr F fs[] = {[] { return V(std::in_place_index<Is>); }...};
  35
  36   std::array<V, N> result = {};
  37   for (auto& v : result) {
  38     v = fs[getRandomInteger(0ul, sizeof...(Is) - 1)]();
  39   }
  40
  41   return result;
  42 }
  43
  44 template <std::size_t N, std::size_t Alts>
  45 static void BM_Visit(benchmark::State& state) {
  46   auto args = genVariants<N>(std::make_index_sequence<Alts>{});
  47   for (auto _ : state) {
  48     benchmark::DoNotOptimize(
  49         std::apply([](auto... vs) { return std::visit([](auto... is) { return (is.v + ... + 0); }, vs...); }, args));
  50   }
  51 }
  52
  53 } // end namespace VariantBenchmarks
  54
  55 #endif // BENCHMARK_VARIANT_BENCHMARKS_H