[llvm] [RISCV] Emit lpad for function with returns-twice attribute (PR #170520)

[Jesse Huang via llvm-commits]

jaidTw wrote:

> Is this a mailing list discussion that you can link to?

Nope, we discuss it personally, I can only link the [related patch](https://patchwork.sourceware.org/project/glibc/patch/20251027042634.2665717-17-jesse.huang@sifive.com/)
But both AArch64 and x86 have taken this approach and all have similar code in their backends (`X86IndirectBranchTracking.cpp` and `AArch64ISelLowering.cpp`)

https://github.com/llvm/llvm-project/pull/170520