[llvm-commits] BlockFrequency for BasicBlocks

[Jakub Staszak]

The new version attached. OK to commit now?

On Jun 17, 2011, at 4:10 PM, Andrew Trick wrote:

> Hi Kuba,
> 
> If you define the constructor and destructor in the .cpp, then do you still need to include InitializePasses.h from BlockFrequency.h.
Done, i also removed "LoopInfo.h"

> And do you really need a "deinit" method?
Yes, if I try to delete BFI in destructor I get a warning ("note: neither the destructor nor the class-specific operator delete will be called, even if they are declared when the class is defined.").

> The block frequency pass should only require a *single* CFG graph traversal. I'm not sure how to do that with LLVM's current rpot/pot iterators. Ideally, LLVM would have a DFSOrder analysis to order the blocks. That ordering will remain valid until some CFG transform.
I removed PO vector, so we have one RPO and one PO traversal now.

> For, now I think you can at least limit it to two traversals (one reverse postorder and one postorder) and add a FIXME so we remember to fold it into one traversal later. Subsequently whenever you need to visit blocks in RPO/PO order, just use the RPO/PO vectors directly.
> 
> Can you also comment that LoopSimplify can make the algorithm converge faster.
Done.

> Can frequency reach zero in divBlockFreq? Don't you want to saturate at 1?
I think it can, so i jest set it to 1/START_FREQ.

- Kuba
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