Tracking time inside a function call - c++

Question

One of my functions is taking more time to execute than expected. It's one of nesteds function and these functions are spread in multiple files across a big project.

function1 (...) {
  function2 (...);
}

function2(...){
  function3(..)
}
...

I am thinking of a way to print time taken by each function call. I am not sure if it's a correct approach. eg:

function1: 1.0 ms
function2: 0.8 ms
function3: 0.1 ms 

Unfortunate I am stuck with an very old compiler gcc-4.1.2. Is there a possibility to trace the timing of all the functions involved in user space without too much modifications in the files (because it is a big project and functions are spread across multiple files). Or If there is a tutorial, please consider pointing me to the link.

Thanks