You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
90 lines
4.5 KiB
HTML
90 lines
4.5 KiB
HTML
<html lang="en">
|
|
<head>
|
|
<title>MMIX-Symbols - Using as</title>
|
|
<meta http-equiv="Content-Type" content="text/html">
|
|
<meta name="description" content="Using as">
|
|
<meta name="generator" content="makeinfo 4.7">
|
|
<link title="Top" rel="start" href="index.html#Top">
|
|
<link rel="up" href="MMIX_002dSyntax.html#MMIX_002dSyntax" title="MMIX-Syntax">
|
|
<link rel="prev" href="MMIX_002dChars.html#MMIX_002dChars" title="MMIX-Chars">
|
|
<link rel="next" href="MMIX_002dRegs.html#MMIX_002dRegs" title="MMIX-Regs">
|
|
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
|
|
<!--
|
|
This file documents the GNU Assembler "as".
|
|
|
|
Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002,
|
|
2006, 2007 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 1.1
|
|
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''.
|
|
|
|
man end-->
|
|
<meta http-equiv="Content-Style-Type" content="text/css">
|
|
<style type="text/css"><!--
|
|
pre.display { font-family:inherit }
|
|
pre.format { font-family:inherit }
|
|
pre.smalldisplay { font-family:inherit; font-size:smaller }
|
|
pre.smallformat { font-family:inherit; font-size:smaller }
|
|
pre.smallexample { font-size:smaller }
|
|
pre.smalllisp { font-size:smaller }
|
|
span.sc { font-variant:small-caps }
|
|
span.roman { font-family: serif; font-weight: normal; }
|
|
--></style>
|
|
</head>
|
|
<body>
|
|
<div class="node">
|
|
<p>
|
|
<a name="MMIX_002dSymbols"></a>Next: <a rel="next" accesskey="n" href="MMIX_002dRegs.html#MMIX_002dRegs">MMIX-Regs</a>,
|
|
Previous: <a rel="previous" accesskey="p" href="MMIX_002dChars.html#MMIX_002dChars">MMIX-Chars</a>,
|
|
Up: <a rel="up" accesskey="u" href="MMIX_002dSyntax.html#MMIX_002dSyntax">MMIX-Syntax</a>
|
|
<hr><br>
|
|
</div>
|
|
|
|
<h5 class="subsubsection">9.23.3.2 Symbols</h5>
|
|
|
|
<p>The character <span class="samp">:</span> is permitted in identifiers. There are two
|
|
exceptions to it being treated as any other symbol character: if a symbol
|
|
begins with <span class="samp">:</span>, it means that the symbol is in the global namespace
|
|
and that the current prefix should not be prepended to that symbol
|
|
(see <a href="MMIX_002dprefix.html#MMIX_002dprefix">MMIX-prefix</a>). The <span class="samp">:</span> is then not considered part of the
|
|
symbol. For a symbol in the label position (first on a line), a <span class="samp">:</span>
|
|
at the end of a symbol is silently stripped off. A label is permitted,
|
|
but not required, to be followed by a <span class="samp">:</span>, as with many other
|
|
assembly formats.
|
|
|
|
<p>The character <span class="samp">@</span> in an expression, is a synonym for <span class="samp">.</span>, the
|
|
current location.
|
|
|
|
<p>In addition to the common forward and backward local symbol formats
|
|
(see <a href="Symbol-Names.html#Symbol-Names">Symbol Names</a>), they can be specified with upper-case <span class="samp">B</span> and
|
|
<span class="samp">F</span>, as in <span class="samp">8B</span> and <span class="samp">9F</span>. A local label defined for the
|
|
current position is written with a <span class="samp">H</span> appended to the number:
|
|
<pre class="smallexample"> 3H LDB $0,$1,2
|
|
</pre>
|
|
<p>This and traditional local-label formats cannot be mixed: a label must be
|
|
defined and referred to using the same format.
|
|
|
|
<p>There's a minor caveat: just as for the ordinary local symbols, the local
|
|
symbols are translated into ordinary symbols using control characters are
|
|
to hide the ordinal number of the symbol. Unfortunately, these symbols
|
|
are not translated back in error messages. Thus you may see confusing
|
|
error messages when local symbols are used. Control characters
|
|
<span class="samp">\003</span> (control-C) and <span class="samp">\004</span> (control-D) are used for the
|
|
MMIX-specific local-symbol syntax.
|
|
|
|
<p>The symbol <span class="samp">Main</span> is handled specially; it is always global.
|
|
|
|
<p>By defining the symbols <span class="samp">__.MMIX.start..text</span> and
|
|
<span class="samp">__.MMIX.start..data</span>, the address of respectively the <span class="samp">.text</span>
|
|
and <span class="samp">.data</span> segments of the final program can be defined, though when
|
|
linking more than one object file, the code or data in the object file
|
|
containing the symbol is not guaranteed to be start at that position; just
|
|
the final executable. See <a href="MMIX_002dloc.html#MMIX_002dloc">MMIX-loc</a>.
|
|
|
|
</body></html>
|
|
|