libcxx/benchmarks/CartesianBenchmarks.h

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include <string>
  10 #include <tuple>
  11 #include <type_traits>
  12 #include <vector>
  13
  14 #include "benchmark/benchmark.h"
  15 #include "test_macros.h"
  16
  17 namespace internal {
  18
  19 template <class D, class E, size_t I>
  20 struct EnumValue : std::integral_constant<E, static_cast<E>(I)> {
  21   static std::string name() { return std::string("_") + D::Names[I]; }
  22 };
  23
  24 template <class D, class E, size_t... Idxs>
  25 constexpr auto makeEnumValueTuple(std::index_sequence<Idxs...>) {
  26   return std::make_tuple(EnumValue<D, E, Idxs>{}...);
  27 }
  28
  29 template <class B>
  30 static auto skip(const B& Bench, int) -> decltype(Bench.skip()) {
  31   return Bench.skip();
  32 }
  33 template <class B>
  34 static auto skip(const B& Bench, char) {
  35   return false;
  36 }
  37
  38 template <class B, class Args, size_t... Is>
  39 void makeBenchmarkFromValuesImpl(const Args& A, std::index_sequence<Is...>) {
  40   for (auto& V : A) {
  41     B Bench{std::get<Is>(V)...};
  42     if (!internal::skip(Bench, 0)) {
  43       benchmark::RegisterBenchmark(Bench.name().c_str(), [=](benchmark::State& S) { Bench.run(S); });
  44     }
  45   }
  46 }
  47
  48 template <class B, class... Args>
  49 void makeBenchmarkFromValues(const std::vector<std::tuple<Args...> >& A) {
  50   makeBenchmarkFromValuesImpl<B>(A, std::index_sequence_for<Args...>());
  51 }
  52
  53 template <template <class...> class B, class Args, class... U>
  54 void makeBenchmarkImpl(const Args& A, std::tuple<U...> t) {
  55   makeBenchmarkFromValues<B<U...> >(A);
  56 }
  57
  58 template <template <class...> class B, class Args, class... U, class... T, class... Tuples>
  59 void makeBenchmarkImpl(const Args& A, std::tuple<U...>, std::tuple<T...>, Tuples... rest) {
  60   (internal::makeBenchmarkImpl<B>(A, std::tuple<U..., T>(), rest...), ...);
  61 }
  62
  63 template <class R, class T>
  64 void allValueCombinations(R& Result, const T& Final) {
  65   return Result.push_back(Final);
  66 }
  67
  68 template <class R, class T, class V, class... Vs>
  69 void allValueCombinations(R& Result, const T& Prev, const V& Value, const Vs&... Values) {
  70   for (const auto& E : Value) {
  71     allValueCombinations(Result, std::tuple_cat(Prev, std::make_tuple(E)), Values...);
  72   }
  73 }
  74
  75 } // namespace internal
  76
  77 // CRTP class that enables using enum types as a dimension for
  78 // makeCartesianProductBenchmark below.
  79 // The type passed to `B` will be a std::integral_constant<E, e>, with the
  80 // additional static function `name()` that returns the stringified name of the
  81 // label.
  82 //
  83 // Eg:
  84 // enum class MyEnum { A, B };
  85 // struct AllMyEnum : EnumValuesAsTuple<AllMyEnum, MyEnum, 2> {
  86 //   static constexpr absl::string_view Names[] = {"A", "B"};
  87 // };
  88 template <class Derived, class EnumType, size_t NumLabels>
  89 using EnumValuesAsTuple =
  90     decltype(internal::makeEnumValueTuple<Derived, EnumType>(std::make_index_sequence<NumLabels>{}));
  91
  92 // Instantiates B<T0, T1, ..., TN> where <Ti...> are the combinations in the
  93 // cartesian product of `Tuples...`, and pass (arg0, ..., argN) as constructor
  94 // arguments where `(argi...)` are the combination in the cartesian product of
  95 // the runtime values of `A...`.
  96 // B<T...> requires:
  97 //  - std::string name(args...): The name of the benchmark.
  98 //  - void run(benchmark::State&, args...): The body of the benchmark.
  99 // It can also optionally provide:
 100 //  - bool skip(args...): When `true`, skips the combination. Default is false.
 101 //
 102 // Returns int to facilitate registration. The return value is unspecified.
 103 template <template <class...> class B, class... Tuples, class... Args>
 104 int makeCartesianProductBenchmark(const Args&... A) {
 105   std::vector<std::tuple<typename Args::value_type...> > V;
 106   internal::allValueCombinations(V, std::tuple<>(), A...);
 107   internal::makeBenchmarkImpl<B>(V, std::tuple<>(), Tuples()...);
 108   return 0;
 109 }
 110
 111 template <class B, class... Args>
 112 int makeCartesianProductBenchmark(const Args&... A) {
 113   std::vector<std::tuple<typename Args::value_type...> > V;
 114   internal::allValueCombinations(V, std::tuple<>(), A...);
 115   internal::makeBenchmarkFromValues<B>(V);
 116   return 0;
 117 }
 118
 119 // When `opaque` is true, this function hides the runtime state of `value` from
 120 // the optimizer.
 121 // It returns `value`.
 122 template <class T>
 123 TEST_ALWAYS_INLINE inline T maybeOpaque(T value, bool opaque) {
 124   if (opaque)
 125     benchmark::DoNotOptimize(value);
 126   return value;
 127 }