[PATCH] D98213: [InlineCost] Enable the cost benefit analysis on FDO

[Wenlei He via Phabricator via llvm-commits]

wenlei added a comment.

In D98213#2620738 <https://reviews.llvm.org/D98213#2620738>, @davidxl wrote:

> It is probably related to MFS -- machine function splitting is not yet well tuned for AutoFDO, and the cost/benefit analysis needs to sync up with that to that for estimating cold size properlly.

Good point. Now I see that costBenefitAnalysis subtracts cold size when estimating, and the cold size is simply dead block size added together based on BFI, assuming they will all be moved out. Without turning on MFS for sample PGO, we would need to skip the cold size subtraction too so they're coordinated. IIRC, MFS was either small regression or neutral for sample PGO?


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