126 lines
5.8 KiB
HTML
126 lines
5.8 KiB
HTML
|
<html lang="en">
|
||
|
|
<head>
|
||
|
|
<title>ESA/390 Directives - 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="ESA_002f390_002dDependent.html#ESA_002f390_002dDependent" title="ESA/390-Dependent">
|
||
|
|
<link rel="prev" href="ESA_002f390-Floating-Point.html#ESA_002f390-Floating-Point" title="ESA/390 Floating Point">
|
||
|
|
<link rel="next" href="ESA_002f390-Opcodes.html#ESA_002f390-Opcodes" title="ESA/390 Opcodes">
|
||
|
|
<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="ESA_002f390-Directives"></a>Next: <a rel="next" accesskey="n" href="ESA_002f390-Opcodes.html#ESA_002f390-Opcodes">ESA/390 Opcodes</a>,
|
||
|
|
Previous: <a rel="previous" accesskey="p" href="ESA_002f390-Floating-Point.html#ESA_002f390-Floating-Point">ESA/390 Floating Point</a>,
|
||
|
|
Up: <a rel="up" accesskey="u" href="ESA_002f390_002dDependent.html#ESA_002f390_002dDependent">ESA/390-Dependent</a>
|
||
|
|
<hr><br>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<h4 class="subsection">9.12.5 ESA/390 Assembler Directives</h4>
|
||
|
|
|
||
|
|
<p><code>as</code> for the ESA/390 supports all of the standard ELF/SVR4
|
||
|
|
assembler directives that are documented in the main part of this
|
||
|
|
documentation. Several additional directives are supported in order
|
||
|
|
to implement the ESA/390 addressing model. The most important of these
|
||
|
|
are <code>.using</code> and <code>.ltorg</code>
|
||
|
|
|
||
|
|
<p><a name="index-ESA_002f390_002donly-directives-813"></a>These are the additional directives in <code>as</code> for the ESA/390:
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><code>.dc</code><dd>A small subset of the usual DC directive is supported.
|
||
|
|
|
||
|
|
<br><dt><code>.drop </code><var>regno</var><dd>Stop using <var>regno</var> as the base register. The <var>regno</var> must
|
||
|
|
have been previously declared with a <code>.using</code> directive in the
|
||
|
|
same section as the current section.
|
||
|
|
|
||
|
|
<br><dt><code>.ebcdic </code><var>string</var><dd>Emit the EBCDIC equivalent of the indicated string. The emitted string
|
||
|
|
will be null terminated. Note that the directives <code>.string</code> etc. emit
|
||
|
|
ascii strings by default.
|
||
|
|
|
||
|
|
<br><dt><code>EQU</code><dd>The standard HLASM-style EQU directive is not supported; however, the
|
||
|
|
standard <code>as</code> directive .equ can be used to the same effect.
|
||
|
|
|
||
|
|
<br><dt><code>.ltorg</code><dd>Dump the literal pool accumulated so far; begin a new literal pool.
|
||
|
|
The literal pool will be written in the current section; in order to
|
||
|
|
generate correct assembly, a <code>.using</code> must have been previously
|
||
|
|
specified in the same section.
|
||
|
|
|
||
|
|
<br><dt><code>.using </code><var>expr</var><code>,</code><var>regno</var><dd>Use <var>regno</var> as the base register for all subsequent RX, RS, and SS form
|
||
|
|
instructions. The <var>expr</var> will be evaluated to obtain the base address;
|
||
|
|
usually, <var>expr</var> will merely be <span class="samp">*</span>.
|
||
|
|
|
||
|
|
<p>This assembler allows two <code>.using</code> directives to be simultaneously
|
||
|
|
outstanding, one in the <code>.text</code> section, and one in another section
|
||
|
|
(typically, the <code>.data</code> section). This feature allows
|
||
|
|
dynamically loaded objects to be implemented in a relatively
|
||
|
|
straightforward way. A <code>.using</code> directive must always be specified
|
||
|
|
in the <code>.text</code> section; this will specify the base register that
|
||
|
|
will be used for branches in the <code>.text</code> section. A second
|
||
|
|
<code>.using</code> may be specified in another section; this will specify
|
||
|
|
the base register that is used for non-label address literals.
|
||
|
|
When a second <code>.using</code> is specified, then the subsequent
|
||
|
|
<code>.ltorg</code> must be put in the same section; otherwise an error will
|
||
|
|
result.
|
||
|
|
|
||
|
|
<p>Thus, for example, the following code uses <code>r3</code> to address branch
|
||
|
|
targets and <code>r4</code> to address the literal pool, which has been written
|
||
|
|
to the <code>.data</code> section. The is, the constants <code>=A(some_routine)</code>,
|
||
|
|
<code>=H'42'</code> and <code>=E'3.1416'</code> will all appear in the <code>.data</code>
|
||
|
|
section.
|
||
|
|
|
||
|
|
<pre class="example"> .data
|
||
|
|
.using LITPOOL,r4
|
||
|
|
.text
|
||
|
|
BASR r3,0
|
||
|
|
.using *,r3
|
||
|
|
B START
|
||
|
|
.long LITPOOL
|
||
|
|
START:
|
||
|
|
L r4,4(,r3)
|
||
|
|
L r15,=A(some_routine)
|
||
|
|
LTR r15,r15
|
||
|
|
BNE LABEL
|
||
|
|
AH r0,=H'42'
|
||
|
|
LABEL:
|
||
|
|
ME r6,=E'3.1416'
|
||
|
|
.data
|
||
|
|
LITPOOL:
|
||
|
|
.ltorg
|
||
|
|
</pre>
|
||
|
|
<p>Note that this dual-<code>.using</code> directive semantics extends
|
||
|
|
and is not compatible with HLASM semantics. Note that this assembler
|
||
|
|
directive does not support the full range of HLASM semantics.
|
||
|
|
|
||
|
|
</dl>
|
||
|
|
|
||
|
|
</body></html>
|
||
|
|
|