[PATCH] D141109: [LoopReroll] Allow for multiple loop control only induction vars

[Joshua Cao via Phabricator via llvm-commits]

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Before this, LoopReroll would fail an assertion, falsely assuming that
there can only possibly a single loop control only induction variable.

For example:

  %a = phi i16 [ %dec2, %for.body ], [ 0, %entry ]
  %b = phi i16 [ %dec1, %for.body ], [ 0, %entry ]
  %a.next = add nsw i16 %1, -1
  %b.next = add nsw i16 %0, -1
  %add = add nsw i16 %a, %b
  ; ... rerollable code
  %cmp.not = icmp eq i16 -10, %add
  br i1 %cmp.not, label %exit, label %loop

Both %a and %b are valid loop control only induction vars

Additionally, some NFC changes to remove unnecessary isa<PHINode> check

Updated complex_reroll checks


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D141109

Files:
  llvm/lib/Transforms/Scalar/LoopRerollPass.cpp
  llvm/test/Transforms/LoopReroll/complex_reroll.ll

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