[LLVMdev] opt and bugs

[Duncan Sands]

Hi John,

> My first question is: When we start running random combinations of 
> passes using opt, which ones should we leave out, because you folks 
> don't want to hear that they're wrong?  For example, the other day I 
> learned that ABCD is not yet ready for this sort of testing.  A while 
> ago someone on the list said something similar about predsimplify 
> (though it looks like that pass has disappeared from the tree?).

check out include/llvm/Support/StandardPasses.h.  All of the passes scheduled
there need to be solid because they are really being used.

> Also I'd appreciate some advice about probabilities for each pass.  For 
> example, it seems like a lot of passes will have little to do if Mem2Reg 
> doesn't run, so perhaps that pass should get >0.5 probability of 
> running.  Does that make sense and do other examples come to mind?

You could start with the list of passes you get at -O3, then randomly
alter it, shifting the pass order, dropping passes and introducing more.
Each run might take too long though due to scheduling many passes.

> Frankly I don't expect a zillion bugs to come out of this but it is 
> super easy and you asked for it :).

Well, we will soon know!

Thanks for doing this,

Duncan.