llvm-project/llvm/test/Transforms/LoopSimplify
Anna Thomas bdb9430917 [BasicBlockUtils] Check for unreachable preds before updating LI in UpdateAnalysisInformation
Summary:
We are incorrectly updating the LI when loop-simplify generates
dedicated exit blocks for a loop. The issue is that there's an implicit
assumption that the Preds passed into UpdateAnalysisInformation are
reachable. However, this is not true and breaks LI by incorrectly
updating the header of a loop.

One such case is when we generate dedicated exits when the exit block is
a landing pad (through SplitLandingPadPredecessors). There maybe other
cases as well, since we do not guarantee that Preds passed in are
reachable basic blocks.

The added test case shows how loop-simplify breaks LI for the outer loop (and DT in turn)
after we try to generate the LoopSimplifyForm.

Reviewers: davide, chandlerc, sanjoy

Reviewed By: davide

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D41519

llvm-svn: 321653
2018-01-02 16:25:50 +00:00
..
2003-04-25-AssertFail.ll
2003-05-12-PreheaderExitOfChild.ll
2003-08-15-PreheadersFail.ll
2003-12-10-ExitBlocksProblem.ll
2004-02-05-DominatorInfoCorruption.ll
2004-03-15-IncorrectDomUpdate.ll
2004-04-01-IncorrectDomUpdate.ll
2004-04-12-LoopSimplify-SwitchBackedges.ll
2004-04-13-LoopSimplifyUpdateDomFrontier.ll
2007-10-28-InvokeCrash.ll
2010-07-15-IncorrectDomFrontierUpdate.ll
2010-12-26-PHIInfiniteLoop.ll
2011-12-14-LandingpadHeader.ll
2012-03-20-indirectbr.ll
ashr-crash.ll
basictest.ll
dbg-loc.ll Remove the obsolete offset parameter from @llvm.dbg.value 2017-07-28 20:21:02 +00:00
dup-preds.ll
hardertest.ll
indirectbr-backedge.ll
indirectbr.ll
merge-exits.ll
notify-scev.ll
phi-node-simplify.ll
pr26682.ll
pr28272.ll
pr30454.ll
pr33494.ll [SCEV] Do not visit nodes twice in containsConstantSomewhere 2017-07-28 06:42:15 +00:00
preserve-llvm-loop-metadata.ll
preserve-scev.ll [SCEV] Teach SCEV to find maxBECount when loop endbound is variant 2017-10-13 14:30:43 +00:00
single-backedge.ll
unreachable-loop-pred.ll [BasicBlockUtils] Check for unreachable preds before updating LI in UpdateAnalysisInformation 2018-01-02 16:25:50 +00:00