[clang] [clang][utils] Add auto mode to reduction script (PR #163282)

[Paul Kirth via cfe-commits]

ilovepi wrote:

> we really need to come up with some sort of testing strategy for this, otherwise I think it'll be very hard to maintain this script and make improvements without breaking things (would need some blessed way to crash the compiler, e.g. `#pragma clang __debug crash` crashes the frontend, need to figure out how to crash the middle/backend). I think I'd prefer that we figure that out before making improvements

why not add an off by default debugging pass we can add to a pipeline that just has a call to __builtin_trap() as its run() impl? could do the same for a machine function pass to check for backend stuff. that's probably good enough for testing purposes.

https://github.com/llvm/llvm-project/pull/163282