Is c++17 & c++20 slower than c++11 or earlier version? [closed]

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I have this code to read lines and words from a large file.

#include <iostream>
#include <vector>
#include <algorithm>
#include <sstream>
#include <iterator>
#include <string>
#include <fstream>
#include <sys/time.h>
#include <boost/regex.hpp>

using namespace std;

bool boostreglike(const string & str, const string & regstr)
{
  boost::regex regexp(regstr);
  boost::smatch matches;
  try{
    return boost::regex_search(str, matches, regexp);
  }catch (exception& e) {
    return false;
  }
  return false;
}

long int curtime()
{
  struct timeval tp;
  gettimeofday(&tp, NULL);
  return tp.tv_sec * 1000 + tp.tv_usec / 1000;
}

main (int argc, char *argv[])
{
  long int thistime = curtime();
  ifstream ifile(argv[2]);
  string strline, str(argv[1]);
  while (std::getline(ifile, strline)){
    if (argc>3){
      std::vector<std::string> tokens;
      std::string token;
      std::stringstream ss(strline);
      while (getline(ss, token, argv[3][0]))
        tokens.push_back(token);
    }
  }
  printf("Time eclapsed %u\n", curtime()-thistime);
}

If I compile it with c++11 or earlier version, it took 6.6s to read a 800M size file.

$ g++ -g test2.cpp -lboost_regex -o test2
$ tim开发者_如何学Goe ./test2 123456789 largefile.txt " "
Time eclapsed 6610

real    0m6.613s
user    0m6.507s
sys     0m0.106s
$ g++ -g -std=c++11 test2.cpp -lboost_regex -o test2_11
$ time ./test2_11 123456789 largefile.txt " "
Time eclapsed 6648

real    0m6.651s
user    0m6.528s
sys     0m0.122s

But if it's compiled with c++17 or c++20, it took 10s.

$ g++ -g -std=c++17 test2.cpp -lboost_regex -o test2_17
$ time ./test2_17 123456789 largefile.txt " "
Time eclapsed 10514

real    0m10.518s
user    0m10.403s
sys     0m0.113s
$ g++ -g -std=c++2a test2.cpp -lboost_regex -o test2_2a
$ time ./test2_2a 123456789 largefile.txt " "
Time eclapsed 10421

real    0m10.424s
user    0m10.313s
sys     0m0.111s

My g++ version is 8.3.1 20190311

I expected to gain better performance in c++17 or c++20, but the actual situation is quite the opposite.

Is it because the implementation of string or vector becomes more complicated or something else?.