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

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hiraditya 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.

Yes, there are some for sure. https://github.com/llvm/llvm-project/issues/168202 is a (draft) list of tests that trigger liveness issues. Out of all, I investigated two for which I have separate bugs linked there.

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