[llvm-branch-commits] [llvm] RegAlloc: Do not fatal error if there are no registers in the alloc order (PR #119640)

[Matt Arsenault via llvm-branch-commits]

arsenm wrote:

This ends up hitting a few machine verifier errors after the error, but I think it's best to fix those separately 

https://github.com/llvm/llvm-project/pull/119640