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

[Alexis Engelke via llvm-commits]

aengelke wrote:

> getNodeIndex() not being inlined maybe?

I briefly looked at Clang's generated assembly code, but it was inlined and I also didn't immediately find something that looked terribly unoptimized. But I didn't spend much time on that. If other users have a problem with that slightly lower performance, adding block numbers there is probably the better way forward. (Bolt's blocks already have an Index and Clang has a BlockId, leaving only VPlan and MLIR.)

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