[llvm] [RISCV64] liveness analysis (PR #167454)

[Craig Topper via llvm-commits]

topperc wrote:

> > Do you intend to make this a full analysis pass that other passes can query?
> 
> Do we need it? The liveness information is in the IR itself, once the kill flags are added. This PR is still missing the update of live-in/live-out set.

Are seeing a lot of incorrect liveins/outs post-RA? I know a lot of the kill flags are missing between isel and the pre-RA LiveVariables pass.

https://github.com/llvm/llvm-project/pull/167454