[PATCH] D151052: [LoopUnroll] Peel iterations based on select, and, or conditions

[Joshua Cao via Phabricator via llvm-commits]

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This allows us to peel this loop with a `and`:

  for (int i = 0; i < N; ++i) {
    if (i % 2 == 0 && i < 3) // can peel based on || as well
      f1();
    f2();

into:

  for (int i = 0; i < 3; ++i) { // peel three iterations
    if (i % 2 == 0)
      f1();
    f2();
  }
  for (int i = 3; i < N; ++i)
    f2();

-----

This also allows us to peel loops with a `select`:

  for (int i = 0; i <= N; ++i);
    f3(i == 0 ? a : b); // select instruction

into:

  f3(a); // peel one iteration
  for (int i = 1; i <= N; ++i)
    f3(b);


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D151052

Files:
  llvm/lib/Transforms/Utils/LoopPeel.cpp
  llvm/test/Transforms/LoopUnroll/peel-loop-conditions.ll

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