[PATCH] D106041: [WIP][SimpleLoopUnswitch] Re-fix introduction of UB when hoisted condition may be undef or poison

[Hyeongyu Kim via Phabricator via llvm-commits]

hyeongyukim updated this revision to Diff 365856.
hyeongyukim added a comment.

While checking the performance regression caused by this patch, I found the following issue:

    Cond.fr = freeze(Cond)
    br Cond.fr, BB_True, BB_False
  BB_True:
    use(Cond.fr)			; Cond.fr is not replaced to true
    ...
  BB_False:
    use(Cond.fr)			; Cond.fr is not repalced to false
    ...

In Original LoopUnswitch, we check the use of invariants and replace them if they are dominated by `LoopPH` or `ClonedPH.`
But while fixing LoopUnswitch, I inserted freeze to `Cond`(which is invariant) and replaced all original uses of `Cond` to `Cond.fr.`
Not only `Cond` but also `Cond.fr` is invariant, but the current implementation doesn't know that `Cond.fr` is invariant.
I added a code and test code(`test1_freeze`) that tells that Cond and Cond.fr are both invariants.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D106041/new/

https://reviews.llvm.org/D106041

Files:
  llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
  llvm/test/Transforms/SimpleLoopUnswitch/ARM/nontrivial-unswitch-cost.ll
  llvm/test/Transforms/SimpleLoopUnswitch/implicit-null-checks.ll
  llvm/test/Transforms/SimpleLoopUnswitch/nontrivial-unswitch.ll

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