21.6 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 21.7 Register Classes. For information on using registers to access a stack frame, see 21.8.3 Registers That Address the Stack Frame. For passing values in registers, see 21.8.6 Passing Arguments in Registers. For returning values in registers, see 21.8.7 How Scalar Function Values Are Returned.

21.6.1 Basic Characteristics of Registers		Number and kinds of registers.
21.6.2 Order of Allocation of Registers		Order in which registers are allocated.
21.6.3 How Values Fit in Registers		What kinds of values each reg can hold.
21.6.4 Handling Leaf Functions		Renumbering registers for leaf functions.
21.6.5 Registers That Form a Stack		Handling a register stack such as 80387.