For whom, mister anonymous?
A simple example. A bug (exception fault) that arises from the interaction of LLVM, MSVC and a 40,000-line post preprocessed C-source. Compile the source to bitcode, feed it to one of their tools and it does a binary chop on the code, excluding bits of it -- in a code-aware manner -- until the trap doesn't occur. Put the bit back that contains the bug and remove other bits. Rinse and repeat until you've excluded everything that doesn't contribute to the trap.
In less than 2 minutes, it reduces 40,000 lines of C, to 680 bytes of bitcode, that converted back amounts to about 12 lines of C. A simple, standalone testcase for further examination.