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144 lines
8.4 KiB
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<title>s390 Directives - Using as</title>
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<meta name="description" content="Using as">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="S_002f390_002dDependent.html#S_002f390_002dDependent" title="S/390-Dependent">
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<link rel="prev" href="s390-Syntax.html#s390-Syntax" title="s390 Syntax">
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<link rel="next" href="s390-Floating-Point.html#s390-Floating-Point" title="s390 Floating Point">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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<!--
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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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<body>
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<div class="node">
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<a name="s390-Directives"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="s390-Floating-Point.html#s390-Floating-Point">s390 Floating Point</a>,
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Previous: <a rel="previous" accesskey="p" href="s390-Syntax.html#s390-Syntax">s390 Syntax</a>,
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Up: <a rel="up" accesskey="u" href="S_002f390_002dDependent.html#S_002f390_002dDependent">S/390-Dependent</a>
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<hr>
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</div>
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<h4 class="subsection">9.41.4 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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<a name="index-g_t_0040code_007b_002einsn_007d-directive_002c-s390-2084"></a>
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<dl><dt><code>.insn</code><dd>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><span class="samp">.insn</span></samp>’ (<a href="s390-Formats.html#s390-Formats">s390 Formats</a>).
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For example, the instruction ‘<samp><span class="samp">l %r1,24(%r15)</span></samp>’ could be written as
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‘<samp><span class="samp">.insn rx,0x58000000,%r1,24(%r15)</span></samp>’.
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<a name="index-g_t_0040code_007b_002eshort_007d-directive_002c-s390-2085"></a><a name="index-g_t_0040code_007b_002elong_007d-directive_002c-s390-2086"></a><a name="index-g_t_0040code_007b_002equad_007d-directive_002c-s390-2087"></a><br><dt><code>.short</code><dt><code>.long</code><dt><code>.quad</code><dd>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><span class="samp">symbol@modifier + constant</span></samp>’,
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‘<samp><span class="samp">symbol@modifier + label + constant</span></samp>’, and
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‘<samp><span class="samp">symbol@modifier - label + constant</span></samp>’.
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The following modifiers are available:
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<dl>
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<dt><code>@got</code><dt><code>@got12</code><dd>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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<br><dt><code>@gotoff</code><dd>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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<br><dt><code>@gotplt</code><dd>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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<br><dt><code>@plt</code><dd>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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<br><dt><code>@pltoff</code><dd>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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<br><dt><code>@tlsgd</code><dt><code>@tlsldm</code><dd>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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<br><dt><code>@gotntpoff</code><dt><code>@indntpoff</code><dd>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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<br><dt><code>@dtpoff</code><dd>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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<br><dt><code>@ntpoff</code><dd>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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</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><span class="samp">ELF Handling For Thread-Local Storage</span></samp>’.
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<p><a name="index-g_t_0040code_007b_002eltorg_007d-directive_002c-s390-2088"></a><br><dt><code>.ltorg</code><dd>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><a name="index-g_t_0040code_007b_002emachine_007d-directive_002c-s390-2089"></a><br><dt><code>.machine </code><var>STRING</var><code>[+</code><var>EXTENSION</var><code>]...</code><dd>
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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>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><a name="index-g_t_0040code_007b_002emachinemode_007d-directive_002c-s390-2090"></a><br><dt><code>.machinemode string</code><dd>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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</dl>
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</body></html>
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