[llvm] [LoongArch] Add codegen support for ILP32D calling convention (PR #141539)

[via llvm-commits]

heiher wrote:

> BTW, does the clang part needs modification? E.g. `clang/lib/CodeGen/Targets/LoongArch.cpp`. But at least we should add some new tests like the existing `abi-lp64d.c`.

Thanks. The clang part will be added in a subsequent patch.

https://github.com/llvm/llvm-project/pull/141539