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213 lines
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213 lines
9.9 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- This file documents the GNU Assembler "as".
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Copyright (C) 1991-2019 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3
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or any later version published by the Free Software Foundation;
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with no Invariant Sections, with no Front-Cover Texts, and with no
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Back-Cover Texts. A copy of the license is included in the
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section entitled "GNU Free Documentation License".
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-->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>s390 Directives (Using as)</title>
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<meta name="description" content="s390 Directives (Using as)">
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<meta name="keywords" content="s390 Directives (Using as)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="AS-Index.html#AS-Index" rel="index" title="AS Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="S_002f390_002dDependent.html#S_002f390_002dDependent" rel="up" title="S/390-Dependent">
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<link href="s390-Floating-Point.html#s390-Floating-Point" rel="next" title="s390 Floating Point">
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<link href="s390-Literal-Pool-Entries.html#s390-Literal-Pool-Entries" rel="prev" title="s390 Literal Pool Entries">
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</head>
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<body lang="en">
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<a name="s390-Directives"></a>
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<div class="header">
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<p>
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Next: <a href="s390-Floating-Point.html#s390-Floating-Point" accesskey="n" rel="next">s390 Floating Point</a>, Previous: <a href="s390-Syntax.html#s390-Syntax" accesskey="p" rel="prev">s390 Syntax</a>, Up: <a href="S_002f390_002dDependent.html#S_002f390_002dDependent" accesskey="u" rel="up">S/390-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>
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</div>
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<hr>
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<a name="Assembler-Directives-8"></a>
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<h4 class="subsection">9.40.4 Assembler Directives</h4>
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<p><code>as</code> for s390 supports all of the standard ELF
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assembler directives as outlined in the main part of this document.
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Some directives have been extended and there are some additional
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directives, which are only available for the s390 <code>as</code>.
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</p>
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<dl compact="compact">
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<dd><a name="index-_002einsn-directive_002c-s390"></a>
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</dd>
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<dt><code>.insn</code></dt>
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<dd><p>This directive permits the numeric representation of an instructions
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and makes the assembler insert the operands according to one of the
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instructions formats for ‘<samp>.insn</samp>’ (<a href="s390-Formats.html#s390-Formats">s390 Formats</a>).
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For example, the instruction ‘<samp>l %r1,24(%r15)</samp>’ could be written as
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‘<samp>.insn rx,0x58000000,%r1,24(%r15)</samp>’.
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<a name="index-_002eshort-directive_002c-s390"></a>
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<a name="index-_002elong-directive_002c-s390"></a>
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<a name="index-_002equad-directive_002c-s390"></a>
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</p></dd>
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<dt><code>.short</code></dt>
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<dt><code>.long</code></dt>
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<dt><code>.quad</code></dt>
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<dd><p>This directive places one or more 16-bit (.short), 32-bit (.long), or
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64-bit (.quad) values into the current section. If an ELF or TLS modifier
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is used only the following expressions are allowed:
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‘<samp>symbol@modifier + constant</samp>’,
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‘<samp>symbol@modifier + label + constant</samp>’, and
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‘<samp>symbol@modifier - label + constant</samp>’.
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The following modifiers are available:
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</p><dl compact="compact">
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<dt><code>@got</code></dt>
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<dt><code>@got12</code></dt>
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<dd><p>The @got modifier can be used for .short, .long and .quad. The @got12
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modifier is synonym to @got. The symbol is added to the GOT. The symbol
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term is replaced with offset from the start of the GOT to the GOT slot for
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the symbol.
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</p></dd>
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<dt><code>@gotoff</code></dt>
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<dd><p>The @gotoff modifier can be used for .short, .long and .quad. The symbol
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term is replaced with the offset from the start of the GOT to the address
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of the symbol.
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</p></dd>
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<dt><code>@gotplt</code></dt>
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<dd><p>The @gotplt modifier can be used for .long and .quad. A procedure linkage
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table entry is generated for the symbol and a jump slot for the symbol
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is added to the GOT. The symbol term is replaced with the offset from the
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start of the GOT to the jump slot for the symbol.
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</p></dd>
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<dt><code>@plt</code></dt>
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<dd><p>The @plt modifier can be used for .long and .quad. A procedure linkage
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table entry us generated for the symbol. The symbol term is replaced with
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the address of the PLT entry for the symbol.
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</p></dd>
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<dt><code>@pltoff</code></dt>
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<dd><p>The @pltoff modifier can be used for .short, .long and .quad. The symbol
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term is replaced with the offset from the start of the PLT to the address
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of the symbol.
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</p></dd>
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<dt><code>@tlsgd</code></dt>
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<dt><code>@tlsldm</code></dt>
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<dd><p>The @tlsgd and @tlsldm modifier can be used for .long and .quad. A
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tls_index structure for the symbol is added to the GOT. The symbol term is
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replaced with the offset from the start of the GOT to the tls_index structure.
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</p></dd>
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<dt><code>@gotntpoff</code></dt>
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<dt><code>@indntpoff</code></dt>
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<dd><p>The @gotntpoff and @indntpoff modifier can be used for .long and .quad.
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The symbol is added to the static TLS block and the negated offset to the
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symbol in the static TLS block is added to the GOT. For @gotntpoff the
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symbol term is replaced with the offset from the start of the GOT to the
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GOT slot, for @indntpoff the symbol term is replaced with the address
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of the GOT slot.
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</p></dd>
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<dt><code>@dtpoff</code></dt>
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<dd><p>The @dtpoff modifier can be used for .long and .quad. The symbol term
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is replaced with the offset of the symbol relative to the start of the
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TLS block it is contained in.
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</p></dd>
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<dt><code>@ntpoff</code></dt>
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<dd><p>The @ntpoff modifier can be used for .long and .quad. The symbol term
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is replaced with the offset of the symbol relative to the TCB pointer.
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</p></dd>
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</dl>
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<p>For more information about the thread local storage modifiers see the
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ELF extension documentation ‘<samp>ELF Handling For Thread-Local Storage</samp>’.
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</p>
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<a name="index-_002eltorg-directive_002c-s390"></a>
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</dd>
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<dt><code>.ltorg</code></dt>
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<dd><p>This directive causes the current contents of the literal pool to be
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dumped to the current location (<a href="s390-Literal-Pool-Entries.html#s390-Literal-Pool-Entries">s390 Literal Pool Entries</a>).
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</p>
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<a name="index-_002emachine-directive_002c-s390"></a>
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</dd>
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<dt><code>.machine <var>STRING</var>[+<var>EXTENSION</var>]…</code></dt>
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<dd>
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<p>This directive allows changing the machine for which code is
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generated. <code>string</code> may be any of the <code>-march=</code>
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selection options, or <code>push</code>, or <code>pop</code>. <code>.machine
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push</code> saves the currently selected cpu, which may be restored with
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<code>.machine pop</code>. Be aware that the cpu string has to be put
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into double quotes in case it contains characters not appropriate
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for identifiers. So you have to write <code>"z9-109"</code> instead of
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just <code>z9-109</code>. Extensions can be specified after the cpu
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name, separated by plus characters. Valid extensions are:
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<code>htm</code>,
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<code>nohtm</code>,
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<code>vx</code>,
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<code>novx</code>.
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They extend the basic instruction set with features from a higher
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cpu level, or remove support for a feature from the given cpu
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level.
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</p>
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<p>Example: <code>z13+nohtm</code> allows all instructions of the z13 cpu
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except instructions from the HTM facility.
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</p>
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<a name="index-_002emachinemode-directive_002c-s390"></a>
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</dd>
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<dt><code>.machinemode string</code></dt>
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<dd><p>This directive allows to change the architecture mode for which code
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is being generated. <code>string</code> may be <code>esa</code>, <code>zarch</code>,
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<code>zarch_nohighgprs</code>, <code>push</code>, or <code>pop</code>.
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<code>.machinemode zarch_nohighgprs</code> can be used to prevent the
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<code>highgprs</code> flag from being set in the ELF header of the output
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file. This is useful in situations where the code is gated with a
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runtime check which makes sure that the code is only executed on
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kernels providing the <code>highgprs</code> feature.
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<code>.machinemode push</code> saves the currently selected mode, which may
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be restored with <code>.machinemode pop</code>.
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</p></dd>
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</dl>
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<hr>
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<div class="header">
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<p>
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Next: <a href="s390-Floating-Point.html#s390-Floating-Point" accesskey="n" rel="next">s390 Floating Point</a>, Previous: <a href="s390-Syntax.html#s390-Syntax" accesskey="p" rel="prev">s390 Syntax</a>, Up: <a href="S_002f390_002dDependent.html#S_002f390_002dDependent" accesskey="u" rel="up">S/390-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>
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</div>
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