1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<!-- This file documents the GNU Assembler "as". 4 5Copyright (C) 1991-2021 Free Software Foundation, Inc. 6 7Permission is granted to copy, distribute and/or modify this document 8under the terms of the GNU Free Documentation License, Version 1.3 9or any later version published by the Free Software Foundation; 10with no Invariant Sections, with no Front-Cover Texts, and with no 11Back-Cover Texts. A copy of the license is included in the 12section entitled "GNU Free Documentation License". 13 --> 14<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ --> 15<head> 16<title>Using as: Xtensa Syntax</title> 17 18<meta name="description" content="Using as: Xtensa Syntax"> 19<meta name="keywords" content="Using as: Xtensa Syntax"> 20<meta name="resource-type" content="document"> 21<meta name="distribution" content="global"> 22<meta name="Generator" content="makeinfo"> 23<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 24<link href="index.html#Top" rel="start" title="Top"> 25<link href="AS-Index.html#AS-Index" rel="index" title="AS Index"> 26<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> 27<link href="Xtensa_002dDependent.html#Xtensa_002dDependent" rel="up" title="Xtensa-Dependent"> 28<link href="Xtensa-Opcodes.html#Xtensa-Opcodes" rel="next" title="Xtensa Opcodes"> 29<link href="Xtensa-Options.html#Xtensa-Options" rel="previous" title="Xtensa Options"> 30<style type="text/css"> 31<!-- 32a.summary-letter {text-decoration: none} 33blockquote.smallquotation {font-size: smaller} 34div.display {margin-left: 3.2em} 35div.example {margin-left: 3.2em} 36div.indentedblock {margin-left: 3.2em} 37div.lisp {margin-left: 3.2em} 38div.smalldisplay {margin-left: 3.2em} 39div.smallexample {margin-left: 3.2em} 40div.smallindentedblock {margin-left: 3.2em; font-size: smaller} 41div.smalllisp {margin-left: 3.2em} 42kbd {font-style:oblique} 43pre.display {font-family: inherit} 44pre.format {font-family: inherit} 45pre.menu-comment {font-family: serif} 46pre.menu-preformatted {font-family: serif} 47pre.smalldisplay {font-family: inherit; font-size: smaller} 48pre.smallexample {font-size: smaller} 49pre.smallformat {font-family: inherit; font-size: smaller} 50pre.smalllisp {font-size: smaller} 51span.nocodebreak {white-space:nowrap} 52span.nolinebreak {white-space:nowrap} 53span.roman {font-family:serif; font-weight:normal} 54span.sansserif {font-family:sans-serif; font-weight:normal} 55ul.no-bullet {list-style: none} 56--> 57</style> 58 59 60</head> 61 62<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> 63<a name="Xtensa-Syntax"></a> 64<div class="header"> 65<p> 66Next: <a href="Xtensa-Optimizations.html#Xtensa-Optimizations" accesskey="n" rel="next">Xtensa Optimizations</a>, Previous: <a href="Xtensa-Options.html#Xtensa-Options" accesskey="p" rel="previous">Xtensa Options</a>, Up: <a href="Xtensa_002dDependent.html#Xtensa_002dDependent" accesskey="u" rel="up">Xtensa-Dependent</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> 67</div> 68<hr> 69<a name="Assembler-Syntax"></a> 70<h4 class="subsection">9.55.2 Assembler Syntax</h4> 71<a name="index-syntax_002c-Xtensa-assembler"></a> 72<a name="index-Xtensa-assembler-syntax"></a> 73<a name="index-FLIX-syntax"></a> 74 75<p>Block comments are delimited by ‘<samp>/*</samp>’ and ‘<samp>*/</samp>’. End of line 76comments may be introduced with either ‘<samp>#</samp>’ or ‘<samp>//</samp>’. 77</p> 78<p>If a ‘<samp>#</samp>’ appears as the first character of a line then the whole 79line is treated as a comment, but in this case the line could also be 80a logical line number directive (see <a href="Comments.html#Comments">Comments</a>) or a preprocessor 81control command (see <a href="Preprocessing.html#Preprocessing">Preprocessing</a>). 82</p> 83<p>Instructions consist of a leading opcode or macro name followed by 84whitespace and an optional comma-separated list of operands: 85</p> 86<div class="smallexample"> 87<pre class="smallexample"><var>opcode</var> [<var>operand</var>, …] 88</pre></div> 89 90<p>Instructions must be separated by a newline or semicolon (‘<samp>;</samp>’). 91</p> 92<p>FLIX instructions, which bundle multiple opcodes together in a single 93instruction, are specified by enclosing the bundled opcodes inside 94braces: 95</p> 96<div class="smallexample"> 97<pre class="smallexample">{ 98[<var>format</var>] 99<var>opcode0</var> [<var>operands</var>] 100</pre><pre class="smallexample"><var>opcode1</var> [<var>operands</var>] 101</pre><pre class="smallexample"><var>opcode2</var> [<var>operands</var>] 102… 103} 104</pre></div> 105 106<p>The opcodes in a FLIX instruction are listed in the same order as the 107corresponding instruction slots in the TIE format declaration. 108Directives and labels are not allowed inside the braces of a FLIX 109instruction. A particular TIE format name can optionally be specified 110immediately after the opening brace, but this is usually unnecessary. 111The assembler will automatically search for a format that can encode the 112specified opcodes, so the format name need only be specified in rare 113cases where there is more than one applicable format and where it 114matters which of those formats is used. A FLIX instruction can also be 115specified on a single line by separating the opcodes with semicolons: 116</p> 117<div class="smallexample"> 118<pre class="smallexample">{ [<var>format</var>;] <var>opcode0</var> [<var>operands</var>]; <var>opcode1</var> [<var>operands</var>]; <var>opcode2</var> [<var>operands</var>]; … } 119</pre></div> 120 121<p>If an opcode can only be encoded in a FLIX instruction but is not 122specified as part of a FLIX bundle, the assembler will choose the 123smallest format where the opcode can be encoded and 124will fill unused instruction slots with no-ops. 125</p> 126<table class="menu" border="0" cellspacing="0"> 127<tr><td align="left" valign="top">• <a href="Xtensa-Opcodes.html#Xtensa-Opcodes" accesskey="1">Xtensa Opcodes</a>:</td><td> </td><td align="left" valign="top">Opcode Naming Conventions. 128</td></tr> 129<tr><td align="left" valign="top">• <a href="Xtensa-Registers.html#Xtensa-Registers" accesskey="2">Xtensa Registers</a>:</td><td> </td><td align="left" valign="top">Register Naming. 130</td></tr> 131</table> 132 133<hr> 134<div class="header"> 135<p> 136Next: <a href="Xtensa-Optimizations.html#Xtensa-Optimizations" accesskey="n" rel="next">Xtensa Optimizations</a>, Previous: <a href="Xtensa-Options.html#Xtensa-Options" accesskey="p" rel="previous">Xtensa Options</a>, Up: <a href="Xtensa_002dDependent.html#Xtensa_002dDependent" accesskey="u" rel="up">Xtensa-Dependent</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> 137</div> 138 139 140 141</body> 142</html> 143