[llvm] [LiveDebugValues] Add a limit on the number of stack slot indexes (PR #225950)

[Scott Linder via llvm-commits]

slinder1 wrote:

I added the original pass writers/maintainers, and also Eric since NVIDIA may have a similar issue.

This is essentially the workaround we have downstream for AMDGPU, but I don't have any better ideas.

For @doru1004 you say "Those targets also tend not to implement
isLoadFromStackSlotPostFE / isStoreToStackSlotPostFE", but I'm not sure I follow. Is this just a coincidence or do we not implement these *because* we have so many subreg indexes?

https://github.com/llvm/llvm-project/pull/225950