[llvm] [AMDGPU] NFC: Provide RPTracker interface for external iterators (PR #93088)

[Jeffrey Byrnes via llvm-commits]

jrbyrnes wrote:

In the latest, I've ported over RP speculation code from the generic trackers to GCN Trackers. While this does introduce code duplication, I thought this to be the better approach than to try to support subreg liveness in generic speculation and introduce generic tracker copies per speculation.

I've tried to organize the git history to ease the burden of review, please let me know if there's something I should do to assist further.

Commits named "Port *" are simple copy/paste of code./
Commits named "Fix * port issues" are minor changes to resolve API / build errors

The most interesting is "Modify behavior to support RP subreg aware RP speculation" which slightly modifies the behavior to support accurate RP speculation.

https://github.com/llvm/llvm-project/pull/93088