<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <!-- This file documents the GNU Assembler "as". Copyright (C) 1991-2020 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 no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License". --> <!-- Created by GNU Texinfo 6.5, http://www.gnu.org/software/texinfo/ --> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>Xtensa Registers (Using as)</title> <meta name="description" content="Xtensa Registers (Using as)"> <meta name="keywords" content="Xtensa Registers (Using as)"> <meta name="resource-type" content="document"> <meta name="distribution" content="global"> <meta name="Generator" content="makeinfo"> <link href="index.html#Top" rel="start" title="Top"> <link href="AS-Index.html#AS-Index" rel="index" title="AS Index"> <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> <link href="Xtensa-Syntax.html#Xtensa-Syntax" rel="up" title="Xtensa Syntax"> <link href="Xtensa-Optimizations.html#Xtensa-Optimizations" rel="next" title="Xtensa Optimizations"> <link href="Xtensa-Opcodes.html#Xtensa-Opcodes" rel="prev" title="Xtensa Opcodes"> <style type="text/css"> <!-- a.summary-letter {text-decoration: none} blockquote.indentedblock {margin-right: 0em} blockquote.smallindentedblock {margin-right: 0em; font-size: smaller} blockquote.smallquotation {font-size: smaller} div.display {margin-left: 3.2em} div.example {margin-left: 3.2em} div.lisp {margin-left: 3.2em} div.smalldisplay {margin-left: 3.2em} div.smallexample {margin-left: 3.2em} div.smalllisp {margin-left: 3.2em} kbd {font-style: oblique} pre.display {font-family: inherit} pre.format {font-family: inherit} pre.menu-comment {font-family: serif} pre.menu-preformatted {font-family: serif} pre.smalldisplay {font-family: inherit; font-size: smaller} pre.smallexample {font-size: smaller} pre.smallformat {font-family: inherit; font-size: smaller} pre.smalllisp {font-size: smaller} span.nolinebreak {white-space: nowrap} span.roman {font-family: initial; font-weight: normal} span.sansserif {font-family: sans-serif; font-weight: normal} ul.no-bullet {list-style: none} --> </style> </head> <body lang="en"> <a name="Xtensa-Registers"></a> <div class="header"> <p> Previous: <a href="Xtensa-Opcodes.html#Xtensa-Opcodes" accesskey="p" rel="prev">Xtensa Opcodes</a>, Up: <a href="Xtensa-Syntax.html#Xtensa-Syntax" accesskey="u" rel="up">Xtensa Syntax</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p> </div> <hr> <a name="Register-Names-21"></a> <h4 class="subsubsection">9.55.2.2 Register Names</h4> <a name="index-Xtensa-register-names"></a> <a name="index-register-names_002c-Xtensa"></a> <a name="index-sp-register"></a> <p>The assembly syntax for a register file entry is the “short” name for a TIE register file followed by the index into that register file. For example, the general-purpose <code>AR</code> register file has a short name of <code>a</code>, so these registers are named <code>a0</code>…<code>a15</code>. As a special feature, <code>sp</code> is also supported as a synonym for <code>a1</code>. Additional registers may be added by processor configuration options and by designer-defined TIE extensions. An initial ‘<samp>$</samp>’ character is optional in all register names. </p> </body> </html>