[PATCH] D116610: [ADCE][NFC] Batch DT updates together

[Jakub Kuderski via Phabricator via llvm-commits]

kuhar added a comment.

> This change is NFC but can improve the runtime of the compiler dramatically in some pathological cases (where the pass was pushing a lot (several thousands) of small updates (less than 6)).
> For instance on the motivating example we went from 300+ sec to less than a second.

Nice!



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Comment at: llvm/lib/Transforms/Scalar/ADCE.cpp:582
   bool Changed = false;
+  SmallVector<DominatorTree::UpdateType, 16> DeletedEdges;
 
----------------
How did you pick this constant? 


================
Comment at: llvm/lib/Transforms/Scalar/ADCE.cpp:636
 
+  if (!DeletedEdges.empty())
+    DomTreeUpdater(DT, &PDT, DomTreeUpdater::UpdateStrategy::Eager)
----------------
How about we move this as an early exit in `DomTreeUpdater::applyUpdates`?


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https://reviews.llvm.org/D116610