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: AArch64 Directives</title> 17 18<meta name="description" content="Using as: AArch64 Directives"> 19<meta name="keywords" content="Using as: AArch64 Directives"> 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="AArch64_002dDependent.html#AArch64_002dDependent" rel="up" title="AArch64-Dependent"> 28<link href="AArch64-Opcodes.html#AArch64-Opcodes" rel="next" title="AArch64 Opcodes"> 29<link href="AArch64-Floating-Point.html#AArch64-Floating-Point" rel="previous" title="AArch64 Floating Point"> 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="AArch64-Directives"></a> 64<div class="header"> 65<p> 66Next: <a href="AArch64-Opcodes.html#AArch64-Opcodes" accesskey="n" rel="next">AArch64 Opcodes</a>, Previous: <a href="AArch64-Floating-Point.html#AArch64-Floating-Point" accesskey="p" rel="previous">AArch64 Floating Point</a>, Up: <a href="AArch64_002dDependent.html#AArch64_002dDependent" accesskey="u" rel="up">AArch64-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="AArch64-Machine-Directives"></a> 70<h4 class="subsection">9.1.5 AArch64 Machine Directives</h4> 71 72<a name="index-machine-directives_002c-AArch64"></a> 73<a name="index-AArch64-machine-directives"></a> 74<dl compact="compact"> 75<dd> 76 77<a name="index-_002earch-directive_002c-AArch64"></a> 78</dd> 79<dt><code>.arch <var>name</var></code></dt> 80<dd><p>Select the target architecture. Valid values for <var>name</var> are the same as 81for the <samp>-march</samp> command-line option. 82</p> 83<p>Specifying <code>.arch</code> clears any previously selected architecture 84extensions. 85</p> 86<a name="index-_002earch_005fextension-directive_002c-AArch64"></a> 87</dd> 88<dt><code>.arch_extension <var>name</var></code></dt> 89<dd><p>Add or remove an architecture extension to the target architecture. Valid 90values for <var>name</var> are the same as those accepted as architectural 91extensions by the <samp>-mcpu</samp> command-line option. 92</p> 93<p><code>.arch_extension</code> may be used multiple times to add or remove extensions 94incrementally to the architecture being compiled for. 95</p> 96 97<a name="index-_002ebss-directive_002c-AArch64"></a> 98</dd> 99<dt><code>.bss</code></dt> 100<dd><p>This directive switches to the <code>.bss</code> section. 101</p> 102 103<a name="index-_002ecpu-directive_002c-AArch64"></a> 104</dd> 105<dt><code>.cpu <var>name</var></code></dt> 106<dd><p>Set the target processor. Valid values for <var>name</var> are the same as 107those accepted by the <samp>-mcpu=</samp> command-line option. 108</p> 109 110<a name="index-_002edword-directive_002c-AArch64"></a> 111</dd> 112<dt><code>.dword <var>expressions</var></code></dt> 113<dd><p>The <code>.dword</code> directive produces 64 bit values. 114</p> 115 116<a name="index-_002eeven-directive_002c-AArch64"></a> 117</dd> 118<dt><code>.even</code></dt> 119<dd><p>The <code>.even</code> directive aligns the output on the next even byte 120boundary. 121</p> 122 123<a name="index-_002efloat16-directive_002c-AArch64"></a> 124</dd> 125<dt><code>.float16 <var>value [,...,value_n]</var></code></dt> 126<dd><p>Place the half precision floating point representation of one or more 127floating-point values into the current section. 128The format used to encode the floating point values is always the 129IEEE 754-2008 half precision floating point format. 130</p> 131 132<a name="index-_002einst-directive_002c-AArch64"></a> 133</dd> 134<dt><code>.inst <var>expressions</var></code></dt> 135<dd><p>Inserts the expressions into the output as if they were instructions, 136rather than data. 137</p> 138 139<a name="index-_002eltorg-directive_002c-AArch64"></a> 140</dd> 141<dt><code>.ltorg</code></dt> 142<dd><p>This directive causes the current contents of the literal pool to be 143dumped into the current section (which is assumed to be the .text 144section) at the current location (aligned to a word boundary). 145GAS maintains a separate literal pool for each section and each 146sub-section. The <code>.ltorg</code> directive will only affect the literal 147pool of the current section and sub-section. At the end of assembly 148all remaining, un-empty literal pools will automatically be dumped. 149</p> 150<p>Note - older versions of GAS would dump the current literal 151pool any time a section change occurred. This is no longer done, since 152it prevents accurate control of the placement of literal pools. 153</p> 154 155 156 157<a name="index-_002epool-directive_002c-AArch64"></a> 158</dd> 159<dt><code>.pool</code></dt> 160<dd><p>This is a synonym for .ltorg. 161</p> 162 163<a name="index-_002ereq-directive_002c-AArch64"></a> 164</dd> 165<dt><code><var>name</var> .req <var>register name</var></code></dt> 166<dd><p>This creates an alias for <var>register name</var> called <var>name</var>. For 167example: 168</p> 169<div class="smallexample"> 170<pre class="smallexample"> foo .req w0 171</pre></div> 172 173<p>ip0, ip1, lr and fp are automatically defined to 174alias to X16, X17, X30 and X29 respectively. 175</p> 176 177 178<a name="index-_002etlsdescadd-directive_002c-AArch64"></a> 179</dd> 180<dt><code><code>.tlsdescadd</code></code></dt> 181<dd><p>Emits a TLSDESC_ADD reloc on the next instruction. 182</p> 183<a name="index-_002etlsdesccall-directive_002c-AArch64"></a> 184</dd> 185<dt><code><code>.tlsdesccall</code></code></dt> 186<dd><p>Emits a TLSDESC_CALL reloc on the next instruction. 187</p> 188<a name="index-_002etlsdescldr-directive_002c-AArch64"></a> 189</dd> 190<dt><code><code>.tlsdescldr</code></code></dt> 191<dd><p>Emits a TLSDESC_LDR reloc on the next instruction. 192</p> 193 194<a name="index-_002eunreq-directive_002c-AArch64"></a> 195</dd> 196<dt><code>.unreq <var>alias-name</var></code></dt> 197<dd><p>This undefines a register alias which was previously defined using the 198<code>req</code> directive. For example: 199</p> 200<div class="smallexample"> 201<pre class="smallexample"> foo .req w0 202 .unreq foo 203</pre></div> 204 205<p>An error occurs if the name is undefined. Note - this pseudo op can 206be used to delete builtin in register name aliases (eg ’w0’). This 207should only be done if it is really necessary. 208</p> 209 210<a name="index-_002evariant_005fpcs-directive_002c-AArch64"></a> 211</dd> 212<dt><code>.variant_pcs <var>symbol</var></code></dt> 213<dd><p>This directive marks <var>symbol</var> referencing a function that may 214follow a variant procedure call standard with different register 215usage convention from the base procedure call standard. 216</p> 217 218<a name="index-_002exword-directive_002c-AArch64"></a> 219</dd> 220<dt><code>.xword <var>expressions</var></code></dt> 221<dd><p>The <code>.xword</code> directive produces 64 bit values. This is the same 222as the <code>.dword</code> directive. 223</p> 224 225<a name="index-_002ecfi_005fb_005fkey_005fframe-directive_002c-AArch64"></a> 226</dd> 227<dt><code><code>.cfi_b_key_frame</code></code></dt> 228<dd><p>The <code>.cfi_b_key_frame</code> directive inserts a ’B’ character into the CIE 229corresponding to the current frame’s FDE, meaning that its return address has 230been signed with the B-key. If two frames are signed with differing keys then 231they will not share the same CIE. This information is intended to be used by 232the stack unwinder in order to properly authenticate return addresses. 233</p> 234</dd> 235</dl> 236 237<hr> 238<div class="header"> 239<p> 240Next: <a href="AArch64-Opcodes.html#AArch64-Opcodes" accesskey="n" rel="next">AArch64 Opcodes</a>, Previous: <a href="AArch64-Floating-Point.html#AArch64-Floating-Point" accesskey="p" rel="previous">AArch64 Floating Point</a>, Up: <a href="AArch64_002dDependent.html#AArch64_002dDependent" accesskey="u" rel="up">AArch64-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> 241</div> 242 243 244 245</body> 246</html> 247