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

[Vikash Gupta via llvm-commits]

vg0204 wrote:

> 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.

While going through it, I found a problem in test case output, need to reassess my changes in PR, currently working on it.

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