[PATCH] D84763: DomTree: Make PostDomTree immune to block successors swap

[Nikita Popov via Phabricator via llvm-commits]

nikic added a comment.

Here's the numbers for this patch: https://llvm-compile-time-tracker.com/compare.php?from=4fdc4d892b988bb9f2e06c3440971d28d6361722&to=63b8e6e79174411d9340790fa5e4f67bc73620a0&stat=instructions There's a measurable impact, but doesn't seem particularly concerning (geomean 0.1% regression).



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Comment at: llvm/include/llvm/Support/GenericDomTreeConstruction.h:392
+      // reverse unreachable nodes.
+      Optional<DenseMap<NodePtr, unsigned>> SuccOrder;
+      auto InitSuccOrderOnce = [&]() {
----------------
You might want to use a SmallDenseMap, as number of successors is usually small.


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  https://reviews.llvm.org/D84763/new/

https://reviews.llvm.org/D84763