[PATCH] D43176: [LoopInterchange] Incrementally update the dominator tree.

Florian Hahn via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Mon Feb 12 14:12:49 PST 2018

fhahn added inline comments.

Comment at: lib/Transforms/Scalar/LoopInterchange.cpp:465
+    AU.addPreserved<DominatorTreeWrapperPass>();
efriedma wrote:
> fhahn wrote:
> > efriedma wrote:
> > > This list of preserved passes seems really short; at the very least, it should preserve GlobalsAA.  Would be nice to preserve LoopInfo, LCSSA, and ScalarEvolution; I think the pass needs to preserve them anyway to interact correctly with itself?
> > Yes, making it preserve the DT is a first step. It indeed relies on  LoopInfo, LCSSA, and ScalarEvolution being preserved too after interchanging 2 loops, for loop nests > 2. 
> > 
> > At least LoopInfo is not preserved properly at the moment. I plan to fix those issues in follow up commits.
> Okay.
> You should probably make DomTree required, to simplify the code; you'll always have it anyway because LoopInfo requires it.
Right, done!


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