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 Immediate Relaxation</title> 17 18<meta name="description" content="Using as: Xtensa Immediate Relaxation"> 19<meta name="keywords" content="Using as: Xtensa Immediate Relaxation"> 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-Relaxation.html#Xtensa-Relaxation" rel="up" title="Xtensa Relaxation"> 28<link href="Xtensa-Directives.html#Xtensa-Directives" rel="next" title="Xtensa Directives"> 29<link href="Xtensa-Jump-Relaxation.html#Xtensa-Jump-Relaxation" rel="previous" title="Xtensa Jump Relaxation"> 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-Immediate-Relaxation"></a> 64<div class="header"> 65<p> 66Previous: <a href="Xtensa-Jump-Relaxation.html#Xtensa-Jump-Relaxation" accesskey="p" rel="previous">Xtensa Jump Relaxation</a>, Up: <a href="Xtensa-Relaxation.html#Xtensa-Relaxation" accesskey="u" rel="up">Xtensa Relaxation</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="Other-Immediate-Field-Relaxation"></a> 70<h4 class="subsubsection">9.55.4.4 Other Immediate Field Relaxation</h4> 71<a name="index-immediate-fields_002c-relaxation"></a> 72<a name="index-relaxation-of-immediate-fields"></a> 73 74<p>The assembler normally performs the following other relaxations. They 75can be disabled by using underscore prefixes (see <a href="Xtensa-Opcodes.html#Xtensa-Opcodes">Opcode Names</a>), the ‘<samp>--no-transform</samp>’ command-line option 76(see <a href="Xtensa-Options.html#Xtensa-Options">Command-line Options</a>), or the 77<code>no-transform</code> directive (see <a href="Transform-Directive.html#Transform-Directive">transform</a>). 78</p> 79<a name="index-MOVI-instructions_002c-relaxation"></a> 80<a name="index-relaxation-of-MOVI-instructions"></a> 81<p>The <code>MOVI</code> machine instruction can only materialize values in the 82range from -2048 to 2047. Values outside this range are best 83materialized with <code>L32R</code> instructions. Thus: 84</p> 85<div class="smallexample"> 86<pre class="smallexample"> movi a0, 100000 87</pre></div> 88 89<p>is assembled into the following machine code: 90</p> 91<div class="smallexample"> 92<pre class="smallexample"> .literal .L1, 100000 93 l32r a0, .L1 94</pre></div> 95 96<a name="index-L8UI-instructions_002c-relaxation"></a> 97<a name="index-L16SI-instructions_002c-relaxation"></a> 98<a name="index-L16UI-instructions_002c-relaxation"></a> 99<a name="index-L32I-instructions_002c-relaxation"></a> 100<a name="index-relaxation-of-L8UI-instructions"></a> 101<a name="index-relaxation-of-L16SI-instructions"></a> 102<a name="index-relaxation-of-L16UI-instructions"></a> 103<a name="index-relaxation-of-L32I-instructions"></a> 104<p>The <code>L8UI</code> machine instruction can only be used with immediate 105offsets in the range from 0 to 255. The <code>L16SI</code> and <code>L16UI</code> 106machine instructions can only be used with offsets from 0 to 510. The 107<code>L32I</code> machine instruction can only be used with offsets from 0 to 1081020. A load offset outside these ranges can be materialized with 109an <code>L32R</code> instruction if the destination register of the load 110is different than the source address register. For example: 111</p> 112<div class="smallexample"> 113<pre class="smallexample"> l32i a1, a0, 2040 114</pre></div> 115 116<p>is translated to: 117</p> 118<div class="smallexample"> 119<pre class="smallexample"> .literal .L1, 2040 120 l32r a1, .L1 121</pre><pre class="smallexample"> add a1, a0, a1 122 l32i a1, a1, 0 123</pre></div> 124 125<p>If the load destination and source address register are the same, an 126out-of-range offset causes an error. 127</p> 128<a name="index-ADDI-instructions_002c-relaxation"></a> 129<a name="index-relaxation-of-ADDI-instructions"></a> 130<p>The Xtensa <code>ADDI</code> instruction only allows immediate operands in the 131range from -128 to 127. There are a number of alternate instruction 132sequences for the <code>ADDI</code> operation. First, if the 133immediate is 0, the <code>ADDI</code> will be turned into a <code>MOV.N</code> 134instruction (or the equivalent <code>OR</code> instruction if the code density 135option is not available). If the <code>ADDI</code> immediate is outside of 136the range -128 to 127, but inside the range -32896 to 32639, an 137<code>ADDMI</code> instruction or <code>ADDMI</code>/<code>ADDI</code> sequence will be 138used. Finally, if the immediate is outside of this range and a free 139register is available, an <code>L32R</code>/<code>ADD</code> sequence will be used 140with a literal allocated from the literal pool. 141</p> 142<p>For example: 143</p> 144<div class="smallexample"> 145<pre class="smallexample"> addi a5, a6, 0 146 addi a5, a6, 512 147</pre><pre class="smallexample"> addi a5, a6, 513 148 addi a5, a6, 50000 149</pre></div> 150 151<p>is assembled into the following: 152</p> 153<div class="smallexample"> 154<pre class="smallexample"> .literal .L1, 50000 155 mov.n a5, a6 156</pre><pre class="smallexample"> addmi a5, a6, 0x200 157 addmi a5, a6, 0x200 158 addi a5, a5, 1 159</pre><pre class="smallexample"> l32r a5, .L1 160 add a5, a6, a5 161</pre></div> 162 163<hr> 164<div class="header"> 165<p> 166Previous: <a href="Xtensa-Jump-Relaxation.html#Xtensa-Jump-Relaxation" accesskey="p" rel="previous">Xtensa Jump Relaxation</a>, Up: <a href="Xtensa-Relaxation.html#Xtensa-Relaxation" accesskey="u" rel="up">Xtensa Relaxation</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> 167</div> 168 169 170 171</body> 172</html> 173