[PATCH] D49974: [GuardWidening] Widen guards with conditions of frequently taken dominated branches

[Max Kazantsev via Phabricator via llvm-commits]

mkazantsev created this revision.
mkazantsev added reviewers: apilipenko, fedor.sergeev, sanjoy, reames.

If there is a frequently taken branch dominated by a guard, and its condition is available
at the point of the guard, we can widen guard with condition of this branch and convert
the branch into unconditional:

  guard(cond1)
  if (cond2) {
    // taken in 99.9% cases
    // do something
  } else {
    // do something else    
  }

Converts to

  guard(cond1 && cond2)
  // do something


https://reviews.llvm.org/D49974

Files:
  lib/Transforms/Scalar/GuardWidening.cpp
  test/Transforms/GuardWidening/widen-frequent-branches.ll

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