GNU Compiler Collection (GCC) Internals

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.