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diff --git a/absl/strings/ascii_benchmark.cc b/absl/strings/ascii_benchmark.cc
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+++ b/absl/strings/ascii_benchmark.cc
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+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/strings/ascii.h"
+
+#include <cctype>
+#include <string>
+#include <array>
+#include <random>
+
+#include "benchmark/benchmark.h"
+
+namespace {
+
+std::array<unsigned char, 256> MakeShuffledBytes() {
+  std::array<unsigned char, 256> bytes;
+  for (size_t i = 0; i < 256; ++i) bytes[i] = static_cast<unsigned char>(i);
+  std::random_device rd;
+  std::seed_seq seed({rd(), rd(), rd(), rd(), rd(), rd(), rd(), rd()});
+  std::mt19937 g(seed);
+  std::shuffle(bytes.begin(), bytes.end(), g);
+  return bytes;
+}
+
+template <typename Function>
+void AsciiBenchmark(benchmark::State& state, Function f) {
+  std::array<unsigned char, 256> bytes = MakeShuffledBytes();
+  size_t sum = 0;
+  for (auto _ : state) {
+    for (unsigned char b : bytes) sum += f(b) ? 1 : 0;
+  }
+  // Make a copy of `sum` before calling `DoNotOptimize` to make sure that `sum`
+  // can be put in a CPU register and not degrade performance in the loop above.
+  size_t sum2 = sum;
+  benchmark::DoNotOptimize(sum2);
+  state.SetBytesProcessed(state.iterations() * bytes.size());
+}
+
+using StdAsciiFunction = int (*)(int);
+template <StdAsciiFunction f>
+void BM_Ascii(benchmark::State& state) {
+  AsciiBenchmark(state, f);
+}
+
+using AbslAsciiIsFunction = bool (*)(unsigned char);
+template <AbslAsciiIsFunction f>
+void BM_Ascii(benchmark::State& state) {
+  AsciiBenchmark(state, f);
+}
+
+using AbslAsciiToFunction = char (*)(unsigned char);
+template <AbslAsciiToFunction f>
+void BM_Ascii(benchmark::State& state) {
+  AsciiBenchmark(state, f);
+}
+
+inline char Noop(unsigned char b) { return static_cast<char>(b); }
+
+BENCHMARK_TEMPLATE(BM_Ascii, Noop);
+BENCHMARK_TEMPLATE(BM_Ascii, std::isalpha);
+BENCHMARK_TEMPLATE(BM_Ascii, absl::ascii_isalpha);
+BENCHMARK_TEMPLATE(BM_Ascii, std::isdigit);
+BENCHMARK_TEMPLATE(BM_Ascii, absl::ascii_isdigit);
+BENCHMARK_TEMPLATE(BM_Ascii, std::isalnum);
+BENCHMARK_TEMPLATE(BM_Ascii, absl::ascii_isalnum);
+BENCHMARK_TEMPLATE(BM_Ascii, std::isspace);
+BENCHMARK_TEMPLATE(BM_Ascii, absl::ascii_isspace);
+BENCHMARK_TEMPLATE(BM_Ascii, std::ispunct);
+BENCHMARK_TEMPLATE(BM_Ascii, absl::ascii_ispunct);
+BENCHMARK_TEMPLATE(BM_Ascii, std::isblank);
+BENCHMARK_TEMPLATE(BM_Ascii, absl::ascii_isblank);
+BENCHMARK_TEMPLATE(BM_Ascii, std::iscntrl);
+BENCHMARK_TEMPLATE(BM_Ascii, absl::ascii_iscntrl);
+BENCHMARK_TEMPLATE(BM_Ascii, std::isxdigit);
+BENCHMARK_TEMPLATE(BM_Ascii, absl::ascii_isxdigit);
+BENCHMARK_TEMPLATE(BM_Ascii, std::isprint);
+BENCHMARK_TEMPLATE(BM_Ascii, absl::ascii_isprint);
+BENCHMARK_TEMPLATE(BM_Ascii, std::isgraph);
+BENCHMARK_TEMPLATE(BM_Ascii, absl::ascii_isgraph);
+BENCHMARK_TEMPLATE(BM_Ascii, std::isupper);
+BENCHMARK_TEMPLATE(BM_Ascii, absl::ascii_isupper);
+BENCHMARK_TEMPLATE(BM_Ascii, std::islower);
+BENCHMARK_TEMPLATE(BM_Ascii, absl::ascii_islower);
+BENCHMARK_TEMPLATE(BM_Ascii, isascii);
+BENCHMARK_TEMPLATE(BM_Ascii, absl::ascii_isascii);
+BENCHMARK_TEMPLATE(BM_Ascii, std::tolower);
+BENCHMARK_TEMPLATE(BM_Ascii, absl::ascii_tolower);
+BENCHMARK_TEMPLATE(BM_Ascii, std::toupper);
+BENCHMARK_TEMPLATE(BM_Ascii, absl::ascii_toupper);
+
+static void BM_StrToLower(benchmark::State& state) {
+  const int size = state.range(0);
+  std::string s(size, 'X');
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(absl::AsciiStrToLower(s));
+  }
+}
+BENCHMARK(BM_StrToLower)->Range(1, 1 << 20);
+
+static void BM_StrToUpper(benchmark::State& state) {
+  const int size = state.range(0);
+  std::string s(size, 'x');
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(absl::AsciiStrToUpper(s));
+  }
+}
+BENCHMARK(BM_StrToUpper)->Range(1, 1 << 20);
+
+}  // namespace