[PATCH] D65148: [SimplifyCFG] Bump phi-node-folding-threshold from 2 to 3

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

Aggressively flattening the CFG has tradeoffs.  If the branch is very unpredictable, or it unblocks some important optimization, it can have a huge benefit.  If you don't fall into one of those cases, you're mildly degrading the performance of a bunch of code, by forcing the execution of instructions where the result isn't used.

I'd like some idea of how often we actually end up with a "select" in the generated code, vs. getting transformed back to a branch by some later pass.  We do some select->branch conversion before isel, and on x86, we also do cmov->branch conversion after isel.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D65148/new/

https://reviews.llvm.org/D65148