That looks like an interesting tool, I'll have to try it out. The program is deterministic given a fixed seed. The bug depends on whether or not optimization i

That looks like an interesting tool, I'll have to try it out. The program is deterministic given a fixed seed. The bug depends on whether or not optimization is on, so it might be in the backend. What I've heard is that the C++ FE in particular still does have some troubles with miscompilations, so that is why I suspect it.