[llvm] [Support][NFC] Use DomTreeBase methods in SemiNCA (PR #101059)

[Jakub Kuderski via llvm-commits]

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@@ -586,7 +586,8 @@ struct SemiNCAInfo {
     // Loop over all of the discovered blocks in the function...
     for (NodePtr W : llvm::drop_begin(NumToNode)) {
       // Don't replace this with 'count', the insertion side effect is important
-      if (DT.DomTreeNodes[W]) continue;  // Haven't calculated this node yet?
+      if (DT.getNode(W))
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kuhar wrote:

WFIW, this refactor makes it less obvious whether `W` is inserted or not. If we do need the insertion, we should update the comment and make this explicit.

Otherwise +1 to what @nikic said above.

https://github.com/llvm/llvm-project/pull/101059