If the type T is a direct interface type (a pointer type), we don't need to call into the runtime to convert a value from type T to an interface{}. If T is such a type, then just making an interface value from the type ptr (a constant) and T itself is all that is needed.

For convT2I, we could also do something similar. If the type is a directInterface type and the itab cache is not nil, we can use that itab cache value directly without calling into the runtime. This is less obviously a win because the generated code still needs the call, and the cache read might need an atomic load.