Integer Fundamental Type Precisions

I'm curious why the IFC specifies `default`, `short`, and `long`, but not `long long` for fundamental type precision?

The IFC writes out:

- `long long` = int w/ 64-bit precision
- `long` = int w/ long precision
- `int` = int w/ default precision

This seems like an odd discrepancy (some builtin types represented via bitwidth and some are represented via a label)? 