[llvm] [AMDGPU][WIP] Optimize SGPR spills (PR #93668)

[Christudasan Devadasan via llvm-commits]

https://github.com/cdevadas commented:

The new test llvm/test/CodeGen/AMDGPU/stack-slot-color-after-sgpr-regalloc.mir needs to be written precisely to show the stack indices being shared. See my previous comments.

https://github.com/llvm/llvm-project/pull/93668