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module/jni/libcxx/benchmarks/VariantBenchmarks.h

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+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef BENCHMARK_VARIANT_BENCHMARKS_H
+#define BENCHMARK_VARIANT_BENCHMARKS_H
+
+#include <array>
+#include <cstddef>
+#include <tuple>
+#include <type_traits>
+#include <variant>
+
+#include "benchmark/benchmark.h"
+
+#include "GenerateInput.h"
+
+namespace VariantBenchmarks {
+
+template <std::size_t I>
+struct S {
+  static constexpr size_t v = I;
+};
+
+template <std::size_t N, std::size_t... Is>
+static auto genVariants(std::index_sequence<Is...>) {
+  using V = std::variant<S<Is>...>;
+  using F = V (*)();
+  static constexpr F fs[] = {[] { return V(std::in_place_index<Is>); }...};
+
+  std::array<V, N> result = {};
+  for (auto& v : result) {
+    v = fs[getRandomInteger(0ul, sizeof...(Is) - 1)]();
+  }
+
+  return result;
+}
+
+template <std::size_t N, std::size_t Alts>
+static void BM_Visit(benchmark::State& state) {
+  auto args = genVariants<N>(std::make_index_sequence<Alts>{});
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(std::apply(
+        [](auto... vs) {
+          return std::visit([](auto... is) { return (is.v + ... + 0); }, vs...);
+        },
+        args));
+  }
+}
+
+} // end namespace VariantBenchmarks
+
+#endif // BENCHMARK_VARIANT_BENCHMARKS_H