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.
83 lines
3.4 KiB
HTML
83 lines
3.4 KiB
HTML
<html lang="en">
|
|
<head>
|
|
<title>RX-Modifiers - Using as</title>
|
|
<meta http-equiv="Content-Type" content="text/html">
|
|
<meta name="description" content="Using as">
|
|
<meta name="generator" content="makeinfo 4.13">
|
|
<link title="Top" rel="start" href="index.html#Top">
|
|
<link rel="up" href="RX_002dDependent.html#RX_002dDependent" title="RX-Dependent">
|
|
<link rel="prev" href="RX_002dOpts.html#RX_002dOpts" title="RX-Opts">
|
|
<link rel="next" href="RX_002dDirectives.html#RX_002dDirectives" title="RX-Directives">
|
|
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
|
|
<!--
|
|
This file documents the GNU Assembler "as".
|
|
|
|
Copyright (C) 1991-2015 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''.
|
|
|
|
-->
|
|
<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; }
|
|
span.sansserif { font-family:sans-serif; font-weight:normal; }
|
|
--></style>
|
|
</head>
|
|
<body>
|
|
<div class="node">
|
|
<a name="RX-Modifiers"></a>
|
|
<a name="RX_002dModifiers"></a>
|
|
<p>
|
|
Next: <a rel="next" accesskey="n" href="RX_002dDirectives.html#RX_002dDirectives">RX-Directives</a>,
|
|
Previous: <a rel="previous" accesskey="p" href="RX_002dOpts.html#RX_002dOpts">RX-Opts</a>,
|
|
Up: <a rel="up" accesskey="u" href="RX_002dDependent.html#RX_002dDependent">RX-Dependent</a>
|
|
<hr>
|
|
</div>
|
|
|
|
<h4 class="subsection">9.37.2 Symbolic Operand Modifiers</h4>
|
|
|
|
<p><a name="index-RX-modifiers-1853"></a><a name="index-syntax_002c-RX-1854"></a><a name="index-g_t_0025gp-1855"></a>
|
|
The assembler supports one modifier when using symbol addresses
|
|
in RX instruction operands. The general syntax is the following:
|
|
|
|
<pre class="smallexample"> %gp(symbol)
|
|
</pre>
|
|
<p>The modifier returns the offset from the <var>__gp</var> symbol to the
|
|
specified symbol as a 16-bit value. The intent is that this offset
|
|
should be used in a register+offset move instruction when generating
|
|
references to small data. Ie, like this:
|
|
|
|
<pre class="smallexample"> mov.W %gp(_foo)[%gpreg], r1
|
|
</pre>
|
|
<p>The assembler also supports two meta register names which can be used
|
|
to refer to registers whose values may not be known to the
|
|
programmer. These meta register names are:
|
|
|
|
|
|
<a name="index-g_t_0040samp_007b_0025gpreg_007d-1856"></a>
|
|
<dl><dt><code>%gpreg</code><dd>The small data address register.
|
|
|
|
<p><a name="index-g_t_0040samp_007b_0025pidreg_007d-1857"></a><br><dt><code>%pidreg</code><dd>The PID base address register.
|
|
|
|
</dl>
|
|
|
|
<p>Both registers normally have the value r13, but this can change if
|
|
some registers have been reserved for use by interrupt handlers or if
|
|
both the small data limit and position independent data features are
|
|
being used at the same time.
|
|
|
|
</body></html>
|
|
|