[llvm] [StackFrameLayoutAnalysis] Support more SlotTypes (PR #100562)

[Hari Limaye via llvm-commits]

hazzlim wrote:

> Better comments never hurt, but I’m fine either way. The offsets are something I’m planning to look into when I get some time.

I've updated the comment to be a bit more explanatory w.r.t. sorting VariableSized slots to the end.

https://github.com/llvm/llvm-project/pull/100562