Measuring effects of a pass on llvm test-suite

I've developed a pass and would like to see it's effects on the running time of the programs on the llvm test-suite. I think that the test-suite has mechanisms for measuring the running time of it's programs. Is that correct? Looking at the doc and other sources, it seemed that I just needed to modify the nightly test somehow. I tried to modify it to include my pass but I didn't find where to put that information. How does the nightly test decides which tests to run?

Basically, how to obtain running time measurements of the programs on the test-suite with and without applying a specific pass?

I guess your best shot is to add option to `llc` which is used to compile
code during test-suite running. That way, you can modify LLCBETAOPTION in
Makefile.programs under test-suite directory to turn on/off your pass.

Regards,
chenwj