[PATCH] D23437: [LoopInfo] Add a routine for verification by recomputation.

[Michael Zolotukhin via llvm-commits]

mzolotukhin created this revision.
mzolotukhin added reviewers: chandlerc, sanjoy, hfinkel.
mzolotukhin added subscribers: silvas, llvm-commits.
Herald added a subscriber: mzolotukhin.

Current implementation of LI verifier isn't ideal and fails to detect
some cases when LI is incorrect. For instance, it checks that all
recorded loops are in a correct form, but it has no way to check if
there are no more other (unrecorded in LI) loops in the function. This
patch adds a way to detect such bugs.

Examples of potential use:
- In PR28888 loop-unroll breaks LI, but we don't detect it (with this
  patch we will).
- IRCE breaks LI in IRCE/with-parent-loops.ll test. I'm xfail-ing this
  test for now (I'll file a separate PR for it).

https://reviews.llvm.org/D23437

Files:
  include/llvm/Analysis/LoopInfo.h
  include/llvm/Analysis/LoopInfoImpl.h
  lib/Analysis/LoopInfo.cpp
  test/Transforms/IRCE/with-parent-loops.ll

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