Newbie question on codeine for SmallString

The LLVM Tutorial,

   https://llvm.org/docs/tutorial/LangImpl01.html

provides an excellent introduction to language definition and code generation.

I am looking for a similar example that demonstrates how to use SmallString. Even a small test program,

Let me explain a bit better. Suppose in a custom language we want to support strings implemented as llvm::SmallString. You can imagine code like this,