[llvm-branch-commits] [llvm] [LivePhysRegs] Add callee-saved regs from MFI in addLiveOutsNoPristines. (PR #73553)

[Matthias Braun via llvm-branch-commits]

MatzeB wrote:

I still feel like I am missing something here, and it's been a while since I looked at this. But my impression is that LLVM modeling is "cheating" a bit in that technically all the callee-saves should be implicit-uses of the return instruction (and not live afterwards) but we don't model it that way and instead make them appear as live-outs of the return block? So doesn't seem like overestimating the liveness because of our current modeling?

If I'm reading your patch correctly it would mean we would start adding all pristine registers for the return block. I am just confused so far because this is happening in a function called `addLiveOutsNoPristines`...

https://github.com/llvm/llvm-project/pull/73553