Hi Janne,
The patch itself looks Ok. One worry, are you introducing an O(N**2)(?) algorithm (looping over all symbols for every symbol?), and does this cause performance issues when compiling some gigantic F77 project?
This is a single pass over the code, so O(N) for the code size. The lookup is O(log M), where M is the number of global symbols in the file, so altogether, we're at O(N*log M), which should be OK. Thanks for the review. Committed as r274551. I will add the documentation about the change in behavior later. Regards Thomas