$ c++ -O2 rcg.cc -o rcg

$ rcg
Usage: rcg [options] function1 function2 ... < rtl-input
[-d]          -- debug, prints into standard error all graph edges (unless
        invoked with -egypt) and include / exclude processing
[-egypt]      -- Graphviz input format created by egypt script. Default is rtl
        format created by gcc -fdump-rtl-expand
[-rtll]       -- standard in is list of rtl file names, one file name per line,
        instead of rtl input
[-no-refs]    -- produce direct call graph, by not including functions
        references when parsing rtl (passing / assigning function addresses)
The prior options control reverse call graph construction.
These options must placed before the following options that control graph
        traversal.
[-i function] -- include call paths with functions names
[-e function] -- exclude call paths with functions names
[-ic]         -- clear include functions list
[-ec]         -- clear exclude functions list
[-il]         -- file with list of include functions, one function name per line
[-el]         -- file with list of exclude functions, one function name per line
[-si]         -- stop traversal if matches function name in include list
        (default); has effect only if include list is not empty; call path with
        excluded functions that occur in the path before include functions will
        not be excluded / filtered out
[-ci]         -- continue traversal if matches include function
With -egypt the input is the output of "egypt" perl script which converts files
        created by gcc -fdump-rtl-expand into Graphviz input format.
The output is call paths for the specified functions / methods.
A practical invocation example:
find path_to_build_directory -type f -name '*.expand' | rcg -rtll function1 function2