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

[Jeremy Morse via llvm-commits]

https://github.com/jmorse commented:

I see this is adding some more intrinsic definitions -- could we avoid this, as open-source LLVM only supports debug records nowadays? If things like the Swift compiler still need intrinsics, this is awkward, especially as we keep on deleting bits of intrinsic support from LLVM.

If you're definitely keeping intrinsic support for the moment, it might want autoupgrade tests and an intrinsic round-trip test.

DbgVariableRecord has helpers like `isAddressOfVariable` and `isValueOfVariable` which are used in a few places in the codebase -- should declare_value return true for any of those? (This probably involves examining the callsites that deal with those).

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