[PATCH] D62989: [Unroll] Do NOT unroll a loop with small runtime upperbound

[Z. Zheng via Phabricator via llvm-commits]

zzheng created this revision.
zzheng added reviewers: efriedma, haicheng.
Herald added a subscriber: dmgreen.
Herald added a project: LLVM.

For a runtime loop if we can compute its trip count upperbound:

      

Don't unroll if:

1. loop is not guaranteed to run either zero or upperbound iterations; and
2. trip count upperbound is less than UnrollMaxUpperBound

If unrolling, limit unroll factor to loop's trip count upperbound.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D62989

Files:
  include/llvm/Transforms/Utils/UnrollLoop.h
  lib/Transforms/Scalar/LoopUnrollAndJamPass.cpp
  lib/Transforms/Scalar/LoopUnrollPass.cpp
  test/Transforms/LoopUnroll/runtime-small-upperbound.ll

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