[PATCH] D118066: [SimplifyCFG] Don't speculatively execute preductably-taken block

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri created this revision.
lebedev.ri added reviewers: spatel, Carrot, reames, nikic.
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Herald added subscribers: wenlei, hiraditya.
lebedev.ri requested review of this revision.

Back in D106650 <https://reviews.llvm.org/D106650> / D106717 <https://reviews.llvm.org/D106717> i've added these profile-guided bailouts,
but i've kept the speculation in the case where there is
a single block to speculate, and we predict it to be taken.

But now, i'm having second thoughts.
If we predict it to be taken, isn't flattening it, 
and incurring the cost of a `select`, a pessimization?


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D118066

Files:
  llvm/lib/Transforms/Utils/SimplifyCFG.cpp
  llvm/test/Transforms/PGOProfile/chr.ll
  llvm/test/Transforms/SimplifyCFG/fold-two-entry-phi-node-with-one-block-profmd.ll
  llvm/test/Transforms/SimplifyCFG/speculatively-execute-block-profmd.ll

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