13.7 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 Register Classes. For information on using registers to access a stack frame, see Frame Registers. For passing values in registers, see Register Arguments. For returning values in registers, see Scalar Return.

• Register Basics: Number and kinds of registers.
• Allocation Order: Order in which registers are allocated.
• Values in Registers: What kinds of values each reg can hold.
• Leaf Functions: Renumbering registers for leaf functions.
• Stack Registers: Handling a register stack such as 80387.