[PATCH] D42637: [PowerPC] Check hot loop exit edge in PPCCTRLoops

[Hiroshi Inoue via Phabricator via llvm-commits]

inouehrs created this revision.
inouehrs added reviewers: hfinkel, echristo, kbarton, nemanjai, jtony, sfertile, lei, syzaara.

PPCCTRLoops transform loops using mtctr/bdnz instructions if loop trip count is known.
But if there is a loop exit edge which is known to be frequently taken (by builtin_expect or by PGO), we should not transform the loop to avoid the cost of mtctr instruction. Here is an example of a loop with hot exit edge:

  for (unsigned i = 0; i < TripCount; i++) {
    // do something
    if (__builtin_expect(check(), 1))
      break;
    // do something
  }




https://reviews.llvm.org/D42637

Files:
  lib/Target/PowerPC/PPCCTRLoops.cpp
  test/CodeGen/PowerPC/ctrloops-hot-exit.ll

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