[llvm] [DebugInfo] Add DW_OP_LLVM_extract_bits (PR #93990)

[Adrian Prantl via llvm-commits]

adrian-prantl wrote:

I see: the value of the 4-bit signed field is `-1`, which is represented as `1111` in binary. And if there are other arithmetic DWARF operations after that would cause a problem for the untyped DWARF stack, where that value would be interpreted as 15 decimal. I think it's reasonable to have signedness bit in the operation under these circumstances. It would be more space-efficient to introduce two separate operations in in `u` and `s` variants, but I don't have any strong opinion either way.

I think I'm fine with this proposal! It would be good to hear at least one more LGTM from others in the @llvm/pr-subscribers-debuginfo group before landing this.

https://github.com/llvm/llvm-project/pull/93990