Register Usage
==============
This section explains how to describe what registers the target
machine has, and how (in general) they can be used.
The description of which registers a specific instruction can use is
done with register classes; see Note:Register Classes. For
information on using registers to access a stack frame, see Note:Frame
Registers. For passing values in registers, see Note:Register
Arguments. For returning values in registers, see Note:Scalar
Return.