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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 See 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::.

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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.
Obsolete Register Macros
Macros formerly used for the 80387.