[PATCH] D46162: [PowerPC] Don't transform to CTR loop if the decrement branch instr. would end up in a different loop

[Nemanja Ivanovic via Phabricator via llvm-commits]

nemanjai created this revision.
nemanjai added reviewers: chandlerc, hfinkel, echristo, kbarton.
Herald added a subscriber: javed.absar.

This fixes PR37229.

Basically, we don't want to transform a loop to a CTR loop if the decrement-and-branch instruction would end up in an exiting block that is also part of another nested loop. Previously this couldn't happen because of how SCEV computed the trip count. However, the check is fundamentally needed.


Repository:
  rL LLVM

https://reviews.llvm.org/D46162

Files:
  lib/Target/PowerPC/PPCCTRLoops.cpp
  test/CodeGen/PowerPC/no-ctr-loop-if-exit-in-nested-loop.ll

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