[PATCH] D58373: [Dominators] Avoid potentially quadratic std::is_permutation

[Jakub Kuderski via Phabricator via llvm-commits]

kuhar added a comment.

`Roots.size()` is only > 1 for the PostDominatorTree, and I'd expect it to be small (< 100) on virtually all functions. `is_permulation` was used in the original code because it doesn't allocate and should be cheaper for small trees.

Do you have some statistics on the size of Roots? At what size does SmallPtrSet start to outperform `is_permuatation`?


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  rL LLVM

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  https://reviews.llvm.org/D58373/new/

https://reviews.llvm.org/D58373