[LLVMdev] Conflicting passes?

[Domagoj D]

Hi Andrew,

> This should really be in the FAQ.  But sufice to say if you make 
> your pass a function pass, you will be fine.
> Andrew

Thx for you reply. 

I think I can squeeze everything into a function pass, but I'd
like to run this by you, just in the case I mixed-up something:
(Chris, I'd also appreciate you wise thoughts on this. I'm sure 
that other users are banging into this wall too.):


Requirements:
- several conflicting passes before myPass
- call runOnFunction in reverse topological order
- have DominatorTree, ETForest, LoopInfo and some other analyses
  available
- possibly, I'll need access to DSAA

Possible solution:
- batch the conflicting transforms
- write myPass as a subclass of FunctionPass
- write myPass.runOnFunction like:
runOnFunction() {
  if (!calledFromPassManager) {
     doStuff();
  }
}
- use CallGraph within myPass.runOnModule, set 
  calledFromPassManager=false, call runOnFunction
  in reverse topological order. This bullet relies
  on the assumption that FunctionPass.runOnModule can
  be freely used without any limitations.
- If I understood correctly, FunctionPasses can use
  ModulePasses (and therefore also DSAA)


Thx.
    Domagoj




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