[libc++][format] Adds formatting benchmarks.

[Mordante]

Summary

These benchmarks will be used to test the performance inpact of the next
set of optimization patches.

[Mordante]

Rebased to trigger CI.

[Mordante]

Retrigger the CI.

[Mordante]

Rebased and attempt to fix the build.

[Mordante]

There seems to be an issue with the benchmark build. Need to investigate.

[vitaut]

Minor comment inline, otherwise LGTM.

libcxx/benchmarks/format_to.bench.cpp

53

Why pass Span as a template parameter instead of the character type?

65

Same here

[Mordante]

Addresses the review comments. That fixes the build locally.
Readd the bytes processed since removing them didn't fix the build.

[Mordante]

Rebased to see whether that fixes the CI.

libcxx/benchmarks/format.bench.cpp

+//===----------------------------------------------------------------------===//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include <format>
+
+#include <string>
+
+#include "benchmark/benchmark.h"
+#include "make_string.h"
+
+#define CSTR(S) MAKE_CSTRING(CharT, S)
+
+template <class CharT>
+static void BM_format_string(benchmark::State& state) {
+  size_t size = state.range(0);
+  std::basic_string<CharT> str(size, CharT('*'));
+
+  while (state.KeepRunningBatch(str.size()))
+    benchmark::DoNotOptimize(std::format(CSTR("{}"), str));
+
+  state.SetBytesProcessed(state.iterations() * size * sizeof(CharT));
+}
+BENCHMARK_TEMPLATE(BM_format_string, char)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_string, wchar_t)->RangeMultiplier(2)->Range(1, 1 << 20);
+
+int main(int argc, char** argv) {
+  benchmark::Initialize(&argc, argv);
+  if (benchmark::ReportUnrecognizedArguments(argc, argv))
+    return 1;
+
+  benchmark::RunSpecifiedBenchmarks();
+}

libcxx/benchmarks/format_to.bench.cpp

+//===----------------------------------------------------------------------===//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include <format>
+
+#include <iterator>
+#include <algorithm>
+#include <array>
+#include <list>
+#include <span>
+#include <string>
+#include <vector>
+
+#include "benchmark/benchmark.h"
+#include "make_string.h"
+
+#define CSTR(S) MAKE_CSTRING(CharT, S)
+
+/*** Back inserter ***/
+
+template <class Container>
+static void BM_format_to_string_back_inserter(benchmark::State& state) {
+  using CharT = typename Container::value_type;
+  size_t size = state.range(0);
+  auto str = std::basic_string<CharT>(size, CharT('*'));
+
+  for (auto _ : state) {
+    Container output;
+    benchmark::DoNotOptimize(std::format_to(std::back_inserter(output), CSTR("{}"), str));
+  }
+  state.SetBytesProcessed(state.iterations() * size * sizeof(CharT));
+}
+
+/*** Begin ***/
+
+template <class Container>
+static void BM_format_to_string_begin(benchmark::State& state) {
+  using CharT = typename Container::value_type;
+  size_t size = state.range(0);
+  auto str = std::basic_string<CharT>(size, CharT('*'));
+
+  Container output(size, CharT('-'));
+  for (auto _ : state)
+    benchmark::DoNotOptimize(std::format_to(std::begin(output), CSTR("{}"), str));
+
+  state.SetBytesProcessed(state.iterations() * size * sizeof(CharT));
+}
+
+/*** Pointer ***/
+
+template <class CharT>
+static void BM_format_to_string_span(benchmark::State& state) {
+  size_t size = state.range(0);
+  auto str = std::basic_string<CharT>(size, CharT('*'));
+
+  auto buffer = std::basic_string<CharT>(size, CharT('-'));
+  std::span<CharT> output{buffer};
+  for (auto _ : state)
+    benchmark::DoNotOptimize(std::format_to(std::begin(output), CSTR("{}"), str));
+
+  state.SetBytesProcessed(state.iterations() * size * sizeof(CharT));
+}
+
+template <class CharT>
+static void BM_format_to_string_pointer(benchmark::State& state) {
+  size_t size = state.range(0);
+  auto str = std::basic_string<CharT>(size, CharT('*'));
+
+  auto buffer = std::basic_string<CharT>(size, CharT('-'));
+  CharT* output = buffer.data();
+  for (auto _ : state)
+    benchmark::DoNotOptimize(std::format_to(output, CSTR("{}"), str));
+
+  state.SetBytesProcessed(state.iterations() * size * sizeof(CharT));
+}
+
+/*** Main ***/
+
+BENCHMARK_TEMPLATE(BM_format_to_string_back_inserter, std::string)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_string_back_inserter, std::vector<char>)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_string_back_inserter, std::list<char>)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_string_begin, std::string)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_string_begin, std::vector<char>)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_string_begin, std::list<char>)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_string_span, char)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_string_pointer, char)->RangeMultiplier(2)->Range(1, 1 << 20);
+
+BENCHMARK_TEMPLATE(BM_format_to_string_back_inserter, std::wstring)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_string_back_inserter, std::vector<wchar_t>)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_string_back_inserter, std::list<wchar_t>)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_string_begin, std::wstring)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_string_begin, std::vector<wchar_t>)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_string_begin, std::list<wchar_t>)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_string_span, wchar_t)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_string_pointer, wchar_t)->RangeMultiplier(2)->Range(1, 1 << 20);
+
+int main(int argc, char** argv) {
+  benchmark::Initialize(&argc, argv);
+  if (benchmark::ReportUnrecognizedArguments(argc, argv))
+    return 1;
+
+  benchmark::RunSpecifiedBenchmarks();
+}

libcxx/benchmarks/format_to_n.bench.cpp

+//===----------------------------------------------------------------------===//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include <format>
+
+#include <iterator>
+#include <algorithm>
+#include <array>
+#include <list>
+#include <span>
+#include <string>
+#include <vector>
+
+#include "benchmark/benchmark.h"
+#include "make_string.h"
+
+#define CSTR(S) MAKE_CSTRING(CharT, S)
+
+/*** Back inserter ***/
+
+template <class Container>
+static void BM_format_to_n_string_back_inserter(benchmark::State& state) {
+  using CharT = typename Container::value_type;
+  size_t size = state.range(0);
+  auto str = std::basic_string<CharT>(2 * size, CharT('*'));
+
+  for (auto _ : state) {
+    Container output;
+    benchmark::DoNotOptimize(std::format_to_n(std::back_inserter(output), size, CSTR("{}"), str));
+  }
+  state.SetBytesProcessed(state.iterations() * size * sizeof(CharT));
+}
+
+/*** Begin ***/
+
+template <class Container>
+static void BM_format_to_n_string_begin(benchmark::State& state) {
+  using CharT = typename Container::value_type;
+  size_t size = state.range(0);
+  auto str = std::basic_string<CharT>(2 * size, CharT('*'));
+
+  Container output(size, CharT('-'));
+  for (auto _ : state)
+    benchmark::DoNotOptimize(std::format_to_n(std::begin(output), size, CSTR("{}"), str));
+
+  state.SetBytesProcessed(state.iterations() * size * sizeof(CharT));
+}
+
+/*** Pointer ***/
+
+template <class CharT>
+static void BM_format_to_n_string_span(benchmark::State& state) {
+  size_t size = state.range(0);
+  auto str = std::basic_string<CharT>(2 * size, CharT('*'));
+
+  auto buffer = std::basic_string<CharT>(size, CharT('-'));
+  std::span<CharT> output{buffer};
+  for (auto _ : state)
+    benchmark::DoNotOptimize(std::format_to_n(std::begin(output), size, CSTR("{}"), str));
+
+  state.SetBytesProcessed(state.iterations() * size * sizeof(CharT));
+}
+
+template <class CharT>
+static void BM_format_to_n_string_pointer(benchmark::State& state) {
+  size_t size = state.range(0);
+  auto str = std::basic_string<CharT>(2 * size, CharT('*'));
+
+  auto buffer = std::basic_string<CharT>(size, CharT('-'));
+  CharT* output = buffer.data();
+  for (auto _ : state)
+    benchmark::DoNotOptimize(std::format_to_n(output, size, CSTR("{}"), str));
+
+  state.SetBytesProcessed(state.iterations() * size * sizeof(CharT));
+}
+
+/*** Main ***/
+
+BENCHMARK_TEMPLATE(BM_format_to_n_string_back_inserter, std::string)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_n_string_back_inserter, std::vector<char>)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_n_string_back_inserter, std::list<char>)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_n_string_begin, std::string)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_n_string_begin, std::vector<char>)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_n_string_begin, std::list<char>)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_n_string_span, char)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_n_string_pointer, char)->RangeMultiplier(2)->Range(1, 1 << 20);
+
+BENCHMARK_TEMPLATE(BM_format_to_n_string_back_inserter, std::wstring)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_n_string_back_inserter, std::vector<wchar_t>)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_n_string_back_inserter, std::list<wchar_t>)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_n_string_begin, std::wstring)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_n_string_begin, std::vector<wchar_t>)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_n_string_begin, std::list<wchar_t>)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_n_string_span, wchar_t)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_format_to_n_string_pointer, wchar_t)->RangeMultiplier(2)->Range(1, 1 << 20);
+
+int main(int argc, char** argv) {
+  benchmark::Initialize(&argc, argv);
+  if (benchmark::ReportUnrecognizedArguments(argc, argv))
+    return 1;
+
+  benchmark::RunSpecifiedBenchmarks();
+}

libcxx/benchmarks/formatted_size.bench.cpp

+//===----------------------------------------------------------------------===//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include <format>
+
+#include <string>
+
+#include "benchmark/benchmark.h"
+#include "make_string.h"
+
+#define CSTR(S) MAKE_CSTRING(CharT, S)
+
+template <class CharT>
+static void BM_formatted_size_string(benchmark::State& state) {
+  size_t size = state.range(0);
+  std::basic_string<CharT> str(size, CharT('*'));
+
+  while (state.KeepRunningBatch(str.size()))
+    benchmark::DoNotOptimize(std::formatted_size(CSTR("{}"), str));
+
+  state.SetBytesProcessed(state.iterations() * size * sizeof(CharT));
+}
+BENCHMARK_TEMPLATE(BM_formatted_size_string, char)->RangeMultiplier(2)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_formatted_size_string, wchar_t)->RangeMultiplier(2)->Range(1, 1 << 20);
+
+int main(int argc, char** argv) {
+  benchmark::Initialize(&argc, argv);
+  if (benchmark::ReportUnrecognizedArguments(argc, argv))
+    return 1;
+
+  benchmark::RunSpecifiedBenchmarks();
+}