Benchmark ways of passing strings to functions

string_copy_elision_benchmark.cpp

#define RUN_ME /*
    g++ -Wall -std=c++17 $(pkg-config benchmark --cflags) -O2 $0 -o $(basename $0 .cpp) $(pkg-config benchmark --libs) -lpthread
    ./$(basename $0 .cpp)
    exit 0
*/

// --------------------------------------------------
// Benchmark           Time           CPU Iterations
// --------------------------------------------------
// BM_r1              52 ns         52 ns   12272152
// BM_r2              30 ns         30 ns   23541703
// BM_r3              36 ns         36 ns   19523162
// BM_r4              27 ns         27 ns   25579177

#include <string>
#include <string_view>
#include <algorithm>
#include <benchmark/benchmark.h>

#define TEXT "abcdefghijklmnopqrstuvwxyz"

using std::string;
using std::string_view;
using std::reverse;

static string reverse_string1(const string &str) {
    string copy = str;
    reverse(begin(copy), end(copy));
    return copy;
}

static string reverse_string2(string str) {
    reverse(begin(str), end(str));
    return str;
}

static string reverse_string3(string_view str) {
    string copy = string(str);
    reverse(begin(copy), end(copy));
    return copy;
}

static string reverse_string4(string_view str) {
    return string(rbegin(str), rend(str));
}

static void BM_r1(benchmark::State& state) {
  for (auto _ : state) {
    benchmark::DoNotOptimize(reverse_string1(TEXT));
  }
}
BENCHMARK(BM_r1);

static void BM_r2(benchmark::State& state) {
  for (auto _ : state) {
    benchmark::DoNotOptimize(reverse_string2(TEXT));
  }
}
BENCHMARK(BM_r2);

static void BM_r3(benchmark::State& state) {
  for (auto _ : state) {
    benchmark::DoNotOptimize(reverse_string3(TEXT));
  }
}
BENCHMARK(BM_r3);

static void BM_r4(benchmark::State& state) {
  for (auto _ : state) {
    benchmark::DoNotOptimize(reverse_string4(TEXT));
  }
}
BENCHMARK(BM_r4);



BENCHMARK_MAIN();