[llvm] [CodeGen][RISCV] Make default describeLoadedValue implementation call getConstValDefinedInReg (PR #77611)

[Philip Reames via llvm-commits]

https://github.com/preames commented:

LGTM from the RISCV perspective.  I'd appreciate someone more familiar with the dwarf ecosystem to chime in.  I'm a bit worried we'll find missing support elsewhere in the toolchain if we start generating the new sub-expression type, but have no real way to quantify this risk.  It's completely possible this is a non-issue.

https://github.com/llvm/llvm-project/pull/77611