[llvm-dev] SimplifyCFG recursion

[Justin Bogner via llvm-dev]

Craig Topper via llvm-dev <llvm-dev at lists.llvm.org> writes:
> SimplifyCFG has many places that do this
>
> return simplifyCFG(BB, TTI, Options) || true;
>
> As far as I can tell this calls the global entry point for SimplifyCFG
> which creates a SimplifyCFGOpt object to call run(BB) on. So I think this
> means SimplifyCFG can create a new SimplifyCFGOpt object each time it
> recurses like this. I don't know how deep it goes in practice.
>
> The global entry point also has a 4th argument called LoopHeaders that is
> defaulted to nullptr. I think we lose the LoopHeaders pointer the first
> time we recurse because none of the recursive calls pass it along.

I agree, it looks like we're dropping this in the recursive calls.

> Should we instead be recursing to the run function on the current
> SimplifyCFGOpt object?

Seems reasonable to me. I don't really see any downside to doing that,
though I'm guessing there may be some bugs/behaviour change since this
will fix the loop headers issue.