[PATCH] D42406: Utils: Fix DomTree update for entry block

[Jakub Kuderski via Phabricator via llvm-commits]

kuhar added inline comments.


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Comment at: lib/Transforms/Utils/BasicBlockUtils.cpp:324
+    if (OldBB == DT->getRootNode()->getBlock()) {
+      assert(NewBB == &NewBB->getParent()->getEntryBlock());
+      DT->setNewRoot(NewBB);
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Can you also add a comment explaining why we need this special case here? I think the reason is that `DT.splitBlock` expects `NewBB` to have a non-empty set of predecessors. 


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Comment at: lib/Transforms/Utils/BasicBlockUtils.cpp:327
+    } else
+      DT->splitBlock(NewBB);
+  }
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Without the patch, was the crash happening inside Split in `GenericDomTree.h`? If it doesn't support it, maybe it would make sense to assert in `DT->split` that `NewBB != getRootNode()` for (forward) dominators?


https://reviews.llvm.org/D42406