C-Reduce is a tool that takes a large C or C++ program that has a
property of interest (such as triggering a compiler bug) and
automatically produces a much smaller C/C++ program that has the same
property. It is intended for use by people who discover and report bugs
in compilers and other tools that process C/C++ code.

A sample run would look like:

$ creduce --n $(nproc) --timing build_and_verify.sh test.i
$ creduce --help