Reducing testcase sets using GCC

[Peter Watkins <peter_watkins@xxxxxxxxxx>]

Our company has a suite of testcases we run before checking in code. 
We'd like to reduce the number of tescases we have to run by running 
only the testcases affected by the source code changes the developer 
made. We have code coverage data for each testcase in the form of 
functions covered. i.e. each testcase knows which C++ functions in our 
product get called when the testcase executes.

I'm trying to determine which functions got changed in our product based 
on the changes a developer made to the source code. So given foo-new.cxx 
and foo-old.cxx, I'd like to know which functions are different between 
these two.

Presently I'm planning on comparing pre-processed copies of the two 
version. i.e. diff foo-new.i foo-old.i. Then from the diff, I'll try to 
determine which functions are changed. However I'm not familiar with 
GCC's plethora of options and debug outputs.

Does GCC provide an easy way of telling if a function or symbol changed 
between two versions of a source file? Has anyone else faced the problem 
of reducing a set of testcases given a set of source code changes? How 
did you solve the problem?

Thanks,

Peter