[PATCH] D125896: [LoopUnroll] Freeze tripcount rather than condition

[Nikita Popov via Phabricator via llvm-commits]

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This is a followup to D125754 <https://reviews.llvm.org/D125754>. We introduce two branches, one before the unrolled loop and one before the epilogue (and similar for the prologue case). The previous patch only froze the condition on the first branch.

Rather than independently freezing the second condition, this patch instead freezes TripCount and bases BECount on it. These are the two quantities involved in the conditions, and this ensures that both work on a consistent, non-poisonous trip count.


https://reviews.llvm.org/D125896

Files:
  llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
  llvm/test/Transforms/LoopUnroll/runtime-loop-at-most-two-exits.ll
  llvm/test/Transforms/LoopUnroll/runtime-loop-multiexit-dom-verify.ll
  llvm/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll
  llvm/test/Transforms/LoopUnroll/runtime-multiexit-heuristic.ll

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