[PATCH] D81236: Improve LegacyPassManager API to correctly report modified status
serge via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Thu Jun 25 02:40:52 PDT 2020
serge-sans-paille marked 2 inline comments as done.
serge-sans-paille added inline comments.
================
Comment at: llvm/lib/Transforms/IPO/LoopExtractor.cpp:135
+ bool Changed = false;
+ LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>(F, &Changed).getLoopInfo();
----------------
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.
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https://reviews.llvm.org/D81236/new/
https://reviews.llvm.org/D81236
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