[LLVMdev] Irreducible Control-Flow & Loops

[Chris Lattner]

On Sep 28, 2009, at 2:28 AM, Ralf Karrenberg wrote:

>
> I am considering writing a patch for LoopInfo instead of creating my  
> own
> data structure for irreducible loops.
> Is such an enhancement desired or even already implemented by someone
> (e.g. in the 2.6 branch)?

I'm not sure that this is a good idea.  LoopInfo is clearly defined to  
represent "natural" loops (where the header dominates the body of the  
loop).  Natural loops have a lot of very useful properties like loop  
headers etc that the loop optimizers depend on.  We already have SCC  
iterators etc, is there a specific reason you want to have LoopInfo do  
this?

If you're writing a pass that converts irreducible control flow to  
reducible loops, I'd think it would be based on SCC iterators, not on  
LoopInfo.

-Chris