<!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>MIPS Symbol Sizes (Using as)</title> <meta name="description" content="MIPS Symbol Sizes (Using as)"> <meta name="keywords" content="MIPS Symbol Sizes (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="MIPS_002dDependent.html#MIPS_002dDependent" rel="up" title="MIPS-Dependent"> <link href="MIPS-Small-Data.html#MIPS-Small-Data" rel="next" title="MIPS Small Data"> <link href="MIPS-Macros.html#MIPS-Macros" rel="prev" title="MIPS Macros"> <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="MIPS-Symbol-Sizes"></a> <div class="header"> <p> Next: <a href="MIPS-Small-Data.html#MIPS-Small-Data" accesskey="n" rel="next">MIPS Small Data</a>, Previous: <a href="MIPS-Macros.html#MIPS-Macros" accesskey="p" rel="prev">MIPS Macros</a>, Up: <a href="MIPS_002dDependent.html#MIPS_002dDependent" accesskey="u" rel="up">MIPS-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> </div> <hr> <a name="Directives-to-override-the-size-of-symbols"></a> <h4 class="subsection">9.27.3 Directives to override the size of symbols</h4> <a name="index-_002eset-sym32"></a> <a name="index-_002eset-nosym32"></a> <p>The n64 ABI allows symbols to have any 64-bit value. Although this provides a great deal of flexibility, it means that some macros have much longer expansions than their 32-bit counterparts. For example, the non-PIC expansion of ‘<samp>dla $4,sym</samp>’ is usually: </p> <div class="smallexample"> <pre class="smallexample">lui $4,%highest(sym) lui $1,%hi(sym) daddiu $4,$4,%higher(sym) daddiu $1,$1,%lo(sym) dsll32 $4,$4,0 daddu $4,$4,$1 </pre></div> <p>whereas the 32-bit expansion is simply: </p> <div class="smallexample"> <pre class="smallexample">lui $4,%hi(sym) daddiu $4,$4,%lo(sym) </pre></div> <p>n64 code is sometimes constructed in such a way that all symbolic constants are known to have 32-bit values, and in such cases, it’s preferable to use the 32-bit expansion instead of the 64-bit expansion. </p> <p>You can use the <code>.set sym32</code> directive to tell the assembler that, from this point on, all expressions of the form ‘<samp><var>symbol</var></samp>’ or ‘<samp><var>symbol</var> + <var>offset</var></samp>’ have 32-bit values. For example: </p> <div class="smallexample"> <pre class="smallexample">.set sym32 dla $4,sym lw $4,sym+16 sw $4,sym+0x8000($4) </pre></div> <p>will cause the assembler to treat ‘<samp>sym</samp>’, <code>sym+16</code> and <code>sym+0x8000</code> as 32-bit values. The handling of non-symbolic addresses is not affected. </p> <p>The directive <code>.set nosym32</code> ends a <code>.set sym32</code> block and reverts to the normal behavior. It is also possible to change the symbol size using the command-line options <samp>-msym32</samp> and <samp>-mno-sym32</samp>. </p> <p>These options and directives are always accepted, but at present, they have no effect for anything other than n64. </p> </body> </html>