<html lang="en"> <head> <title>Registers - GNU Compiler Collection (GCC) Internals</title> <meta http-equiv="Content-Type" content="text/html"> <meta name="description" content="GNU Compiler Collection (GCC) Internals"> <meta name="generator" content="makeinfo 4.13"> <link title="Top" rel="start" href="index.html#Top"> <link rel="up" href="Target-Macros.html#Target-Macros" title="Target Macros"> <link rel="prev" href="Type-Layout.html#Type-Layout" title="Type Layout"> <link rel="next" href="Register-Classes.html#Register-Classes" title="Register Classes"> <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> <!-- Copyright (C) 1988-2015 Free Software Foundation, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with the Invariant Sections being ``Funding Free Software'', the Front-Cover Texts being (a) (see below), and with the Back-Cover Texts being (b) (see below). A copy of the license is included in the section entitled ``GNU Free Documentation License''. (a) The FSF's Front-Cover Text is: A GNU Manual (b) The FSF's Back-Cover Text is: You have freedom to copy and modify this GNU Manual, like GNU software. Copies published by the Free Software Foundation raise funds for GNU development.--> <meta http-equiv="Content-Style-Type" content="text/css"> <style type="text/css"><!-- pre.display { font-family:inherit } pre.format { font-family:inherit } pre.smalldisplay { font-family:inherit; font-size:smaller } pre.smallformat { font-family:inherit; font-size:smaller } pre.smallexample { font-size:smaller } pre.smalllisp { font-size:smaller } span.sc { font-variant:small-caps } span.roman { font-family:serif; font-weight:normal; } span.sansserif { font-family:sans-serif; font-weight:normal; } --></style> </head> <body> <div class="node"> <a name="Registers"></a> <p> Next: <a rel="next" accesskey="n" href="Register-Classes.html#Register-Classes">Register Classes</a>, Previous: <a rel="previous" accesskey="p" href="Type-Layout.html#Type-Layout">Type Layout</a>, Up: <a rel="up" accesskey="u" href="Target-Macros.html#Target-Macros">Target Macros</a> <hr> </div> <h3 class="section">17.7 Register Usage</h3> <p><a name="index-register-usage-4044"></a> This section explains how to describe what registers the target machine has, and how (in general) they can be used. <p>The description of which registers a specific instruction can use is done with register classes; see <a href="Register-Classes.html#Register-Classes">Register Classes</a>. For information on using registers to access a stack frame, see <a href="Frame-Registers.html#Frame-Registers">Frame Registers</a>. For passing values in registers, see <a href="Register-Arguments.html#Register-Arguments">Register Arguments</a>. For returning values in registers, see <a href="Scalar-Return.html#Scalar-Return">Scalar Return</a>. <ul class="menu"> <li><a accesskey="1" href="Register-Basics.html#Register-Basics">Register Basics</a>: Number and kinds of registers. <li><a accesskey="2" href="Allocation-Order.html#Allocation-Order">Allocation Order</a>: Order in which registers are allocated. <li><a accesskey="3" href="Values-in-Registers.html#Values-in-Registers">Values in Registers</a>: What kinds of values each reg can hold. <li><a accesskey="4" href="Leaf-Functions.html#Leaf-Functions">Leaf Functions</a>: Renumbering registers for leaf functions. <li><a accesskey="5" href="Stack-Registers.html#Stack-Registers">Stack Registers</a>: Handling a register stack such as 80387. </ul> </body></html>