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

[Ehud Katz via Phabricator via llvm-commits]

ekatz added inline comments.


================
Comment at: llvm/lib/Transforms/IPO/LoopExtractor.cpp:135
+  bool Changed = false;
+  LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>(F, &Changed).getLoopInfo();
 
----------------
mehdi_amini wrote:
> ekatz wrote:
> > 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.
> What is "on the fl pass evaluation" in this context? I'm missing why `BreakCriticalEdges` isn't triggered before `LoopExtractor::runOnFunction` invocation?
To add to your question, just to make sure I understand it correctly- if `getAnalysis` was never called, then `BreakCriticalEdges` wasn't either?


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

https://reviews.llvm.org/D81236