[llvm] [RISCV][GISel] Support passing arguments through the stack. (PR #69289)

[Min-Yih Hsu via llvm-commits]

mshockwave wrote:

> I saw this was approved but WIP is in the title. Please change before commit.

Right, please also remember to update the commit message too as the tests have been added.

https://github.com/llvm/llvm-project/pull/69289