On Mon, 2007-07-23 at 09:58 -0500, Dan Gohman wrote: > > + // If we can show that there is no inner cycle in the loop then we know > > + // that the execution count must equal the branch count. > > Would it be too intrusive to ask ScalarEvolution to use a > PostDominanceFrontier for this?
No, that's what I implemented at first. Unfortunately, it doesn't cover all the possible cases (specifically, it broke 2007-01-06-TripCount.ll). In 2007-01-06-TripCount.ll there's two "loops" sharing one loop header. The first runs from header -> exit -> A -> header and the other is header -> B -> A -> header. I was testing exit postdom header, which it does, but that didn't catch this case where the transform is still unsafe. If you think I merely had my test wrong, please let me know what you think it ought to be and I'll implement it and see. Nick _______________________________________________ llvm-commits mailing list llvm-commits@cs.uiuc.edu http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
