[llvm] [Support] Store dominator tree nodes in a vector (PR #101705)

[Nikita Popov via llvm-commits]

nikic wrote:

> [c-t-t](http://llvm-compile-time-tracker.com/compare.php?from=e7f9d8e5c3e49e729c69aaa9be3322f7902370b8&to=5b907f0f5c34fcaf20ad1caa8e53b7d616e75c8d&stat=instructions:u). The extra indirection map->vector costs 0.2% (interestingly, there's no effect in stage1-O3). I'd like to keep nodes in a single place, though, because it makes code a lot more simple.

Interesting. Sounds like an optimization failure in clang that doesn't occur in gcc. getNodeIndex() not being inlined maybe?

https://github.com/llvm/llvm-project/pull/101705