[PATCH] D81236: Improve LegacyPassManager API to correctly report modified status

[Ehud Katz via Phabricator via llvm-commits]

ekatz accepted this revision.
ekatz added a comment.
This revision is now accepted and ready to land.

I admit, I don't like this change. This is a work around a design flaw in the old PM. However, it seems like the right decision to handle it, right now.
I think we should post a RFC for a new - *cough* - PM... ;)

LGTM, but please separate the patch into two: the PM related; and the LoopExtractor.



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Comment at: llvm/lib/Transforms/IPO/LoopExtractor.cpp:135
+  bool Changed = false;
+  LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>(F, &Changed).getLoopInfo();
 
----------------
serge-sans-paille wrote:
> ekatz wrote:
> > jdoerfert wrote:
> > > ekatz wrote:
> > > > Maybe I am missing something, but isn't `LoopExtractor` dependent on `BreakCriticalEdges`? I mean, what are the transformations that the `LoopInfo` analysis depends on?
> > > > what are the transformations that the LoopInfo analysis depends on?
> > > 
> > > No transformations:
> > > 
> > > ```
> > >   void LoopInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {                                                                                                                                              
> > >     AU.setPreservesAll();
> > >     AU.addRequiredTransitive<DominatorTreeWrapperPass>();
> > >   }
> > >   
> > > ```
> > So why would the `Changed` ever be set to `true`?
> It's set to True because of the on the fly pass evaluation: asking for `LoopInfo` triggers the whole dependencies, including `BreakCriticalEdges`. That's why the API change I propose only impacts on the fly passes.
I see.


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  https://reviews.llvm.org/D81236/new/

https://reviews.llvm.org/D81236