[llvm] [Codegen] (NFC) Faster algorithm for MachineBlockPlacement (PR #91843)

[Mingming Liu via llvm-commits]

minglotus-6 wrote:

fwiw, https://llvm-compile-time-tracker.com/ is often used to measure compile-time changes for upstream changes. It has a ThinLTO set-up but there isn't one for PGO. https://llvm-compile-time-tracker.com/about.php has the instructions if you are interested.

https://github.com/llvm/llvm-project/pull/91843