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

[Jun Bum Lim via llvm-commits]

junbuml added a comment.

> @danielcdh:  Could you point me to the original test case?


In my first posting in Diff 1, I added a test case (aarch64-skip-merging-case-block.ll) which was reduced from the benchmark I was targeting.

> @davidxl: Given the limitation of MachineSink pass to split critical edges later (for the switch case), the effect of creating critical edge in CGP here can be quite detrimental, so we should probably make the patch more general -- instead of checking just switch inst in Predecessor, check indirect branch as well. Perhaps also adding some cost related heuristic -- by checking the number of phis (with incoming value from Pred) in the Succ block.


Thanks David for the detail. What you describe here is exactly what I observed. Based on your comment, I will update this change to avoid creating critical edges in case when potential sinkables cannot be handled in later pass (MachineSink);  it's going to be more general to cover indirect branches as well, and a simple cost heuristic will be added  based on the number of phis in Succ.


https://reviews.llvm.org/D22696