One the subject of porting code from one language to another (ignoring that the headline says "rewrite", which implies more than a dumb port). Are there any to

One the subject of porting code from one language to another (ignoring that the headline says "rewrite", which implies more than a dumb port). Are there any tools to help map out the work that needs to be done? I found myself doing this by hand recently, doing graph search on a piece of paper. I needed to port one function, so I identified all the functions that function called, wrote them down, and then looked into the next layer of functions etc. I manually searched the potential call graphs by reading the code and wrote down all possible functions involved. I then crossed of functions that seemed obvious, such as a function to retrieve the value of a dictionary with a default value, such simple functions are trivial and need no special effort. In the end I had a list of functions that needed to be ported one-by-one and I began working from the bottom up. I was wondering if there are any tools that could automate this process? It seems to be the beginning of a source-to-source compiler, but such a compiler could be kept simple by embracing that most of the work can be presented to a human to perform manually. The "compilers" only job is to structure the work and break it down into small chunks.