There were some discussions here about -ftime-trace. I've written a GCC
plugin with similar functionality last year:
https://github.com/royjacobson/externis. It works at least on GCC11 and
GCC12.
It was written by practically reverse engineering the GCC AST and can only
make use of the GCC plugin callbacks, which are very limited, so the
information it provides is sometimes inaccurate and heuristic. But maybe it
can help by providing something to iterate on.

Cheers,
Roy