Does evaluating 'else if' take as much CPU time as evaluating 'if' in C?

Initial assumption: We will run the following programs 1000 times with argv[1] not being NULL :

#include<stdio.h>
#include<stdlib.h>


int main( int argc, char *argv[] )  {
 
 if ( argv[1] == NULL ) {
  printf("Usage: a.out argument1");
  exit(1);
}
 else if ( argv[1] != NULL ) {
    
    some_expensive_computation;
    
   
   }

return 0;   
}

Will the above code run faster in such case than the following:

#include<stdio.h>
#include<stdlib.h>


int main( int argc, char *argv[] )  {
 
 if ( argv[1] == NULL ) {
  printf("Usage: a.out argument1");
  exit(1);
}
 if ( argv[1] != NULL ) {
    
    some_expensive_computation;
    
   
   }

return 0;   
}

I've already learned that the fastest code would make use of else instead of else if. Does evaluating 'else if' take as much CPU time as evaluating 'if' in C?