[PATCH] D22696: [CodeGenPrep] Skip merging empty case blocks

[Jun Bum Lim via llvm-commits]

junbuml added a comment.

- In PGO I can see just noise level regression (-0.5%) with this patch with FreqRatio=2.
- In Evaluate_TPat(), I can see 10 empty case blocks were applied in this patch, resulting in 10 more branches in the final assembly in aarch64 with -mcpu=kryo.  Since SimplifyCFG also merge empty blocks in TryToSimplifyUncondBranchFromEmptyBlock(), making a simple case hit in CGP  require quite complex testcase. That's why I removed my first testcase in Diff1 (aarch64-skip-merging-case-block.ll). Please let me know if you really need a reduce testcase.
- As of now, in this patch I believe we need to keep the default FreqRatio conservative, so I want to set it 1000, which I believe conservative enough.


https://reviews.llvm.org/D22696