[llvm] Add new llvm.dbg.declare_value intrinsic. (PR #168132)

[Felipe de Azevedo Piovezan via llvm-commits]

https://github.com/felipepiovezan commented:

This LGTM (left some ideas for the docs).

To take a step back, and definitely outside of anything to be changed in this PR, why do we require the value to be in the entry BB? What if a variable has a single value in the entire function but its value is only available later?

https://github.com/llvm/llvm-project/pull/168132