benchmark libxml2 strlen - https://gitlab.gnome.org/GNOME/libxml2/-/merge_requests/147

benchmark.c

#include <stdlib.h>
#include <stdio.h>
#include <sys/time.h>
#include <string.h>
#include <limits.h>

long time_in_ms()
{
  struct timeval  tv;
  gettimeofday(&tv, NULL);

  return (tv.tv_sec) * 1000 + (tv.tv_usec) / 1000.0 ;
}

long elapsed_ms_since(long start)
{
  return time_in_ms() - start ;
}

#define N_ITERATIONS 10000000

int xmlStrlen(const char *str);
int xmlStrlenFast(const char* str);

static int xmlStrlenStatic(const char* str) {
    size_t len = str ? strlen((const char *)str) : 0;
    return(len > INT_MAX ? 0 : len);
}

int main(int argc, char **argv)
{
  int sizes[] = { 1, 2, 3, 4, 8, 16, 32, 64, 128, 256, 512 };
  int sizes_len = sizeof(sizes) / sizeof(int);
  long start_time, elapsed_ms;
  int j, jsize;

  printf("iterating %d times ...\n\n", N_ITERATIONS);
  printf("%10s %12s %12s %12s %12s\n", "", "v2.9.13", "baseline", "#147", "#115");
  printf("%10s %12s %12s %12s %12s\n", "length", "xmlStrlen()", "strlen()", "xmlFast()", "xmlStatic()");

  for (jsize = 0 ; jsize < sizes_len ; ++jsize) {
    char *subject = malloc(sizes[jsize]+1);
    for (j = 0 ; j < sizes[jsize] ; ++j) {
      subject[j] = 'x';
    }
    subject[sizes[jsize]] = 0;
    printf("%10d", sizes[jsize]);

    start_time = time_in_ms();
    for (j = 0 ; j < N_ITERATIONS ; ++j) {
      if (xmlStrlen(subject) != sizes[jsize]) { abort(); }
      subject[0] = 'x';
    }
    printf(" %9ld ms", elapsed_ms_since(start_time));

    start_time = time_in_ms();
    for (j = 0 ; j < N_ITERATIONS ; ++j) {
      if (strlen(subject) != sizes[jsize]) { abort(); }
      subject[0] = 'x';
    }
    printf(" %9ld ms", elapsed_ms_since(start_time));

    start_time = time_in_ms();
    for (j = 0 ; j < N_ITERATIONS ; ++j) {
      if (xmlStrlenFast(subject) != sizes[jsize]) { abort(); }
      subject[0] = 'x';
    }
    printf(" %9ld ms", elapsed_ms_since(start_time));

    start_time = time_in_ms();
    for (j = 0 ; j < N_ITERATIONS ; ++j) {
      if (xmlStrlenStatic(subject) != sizes[jsize]) { abort(); }
      subject[0] = 'x';
    }
    printf(" %9ld ms", elapsed_ms_since(start_time));

    printf("\n");
    free(subject);
  }
  printf("\n");
  exit(0);
}

lib.c

#include <string.h>
#include <limits.h>

int xmlStrlen(const char *str) {
    size_t len = 0;

    if (str == NULL) return(0);
    while (*str != 0) { /* non input consuming */
        str++;
        len++;
    }
    return(len > INT_MAX ? 0 : len);
}

int xmlStrlenFast(const char* str) {
    size_t len = str ? strlen((const char *)str) : 0;
    return(len > INT_MAX ? 0 : len);
}

Makefile

CFLAGS = -std=c89

default: run


benchmark-O0.o: benchmark.c
	$(CC) -O0 $(CFLAGS) -c -o benchmark-O0.o benchmark.c

lib-O0.o: lib.c
	$(CC) -O0 $(CFLAGS) -c -o lib-O0.o lib.c

benchmark-O0: benchmark-O0.o lib-O0.o
	$(CC) -O0 $(CFLAGS) -o benchmark-O0 benchmark-O0.o lib-O0.o


benchmark-O1.o: benchmark.c
	$(CC) -O1 $(CFLAGS) -c -o benchmark-O1.o benchmark.c

lib-O1.o: lib.c
	$(CC) -O1 $(CFLAGS) -c -o lib-O1.o lib.c

benchmark-O1: benchmark-O1.o lib-O1.o
	$(CC) -O1 $(CFLAGS) -o benchmark-O1 benchmark-O1.o lib-O1.o


benchmark-O2.o: benchmark.c
	$(CC) -O2 $(CFLAGS) -c -o benchmark-O2.o benchmark.c

lib-O2.o: lib.c
	$(CC) -O2 $(CFLAGS) -c -o lib-O2.o lib.c

benchmark-O2: benchmark-O2.o lib-O2.o
	$(CC) -O2 $(CFLAGS) -o benchmark-O2 benchmark-O2.o lib-O2.o


benchmark-O3.o: benchmark.c
	$(CC) -O3 $(CFLAGS) -c -o benchmark-O3.o benchmark.c

lib-O3.o: lib.c
	$(CC) -O3 $(CFLAGS) -c -o lib-O3.o lib.c

benchmark-O3: benchmark-O3.o lib-O3.o
	$(CC) -O3 $(CFLAGS) -o benchmark-O3 benchmark-O3.o lib-O3.o


all: benchmark-O0 benchmark-O1 benchmark-O2 benchmark-O3

run: all
	./benchmark-O0
	./benchmark-O1
	./benchmark-O2
	./benchmark-O3

clean:
	rm -f benchmark-O* *.o