[PATCH] D43256: [MBP] Move a latch block with conditional exit and multi predecessors to top of loop

[Guozhi Wei via Phabricator via llvm-commits]

Carrot added a comment.

Thanks for the test case, I can reproduce it now.

As I suspected, the problem is in BranchProbabilityAnalysis. For floating point unorder comparison, it estimates the probability as 12/32. While for loop exit, the probability is 3.1%. With these probability numbers, move the latch before header is beneficial. Unfortunately there is never NaN in the input.

Even for a normal program, the NaN possibility is extremely rare, we should give a much smaller number for the unordered comparison.


Repository:
  rL LLVM

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  https://reviews.llvm.org/D43256/new/

https://reviews.llvm.org/D43256