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230 lines
8.8 KiB
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230 lines
8.8 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>AArch64 Directives (Using as)</title>
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<meta name="description" content="AArch64 Directives (Using as)">
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<meta name="keywords" content="AArch64 Directives (Using as)">
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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="AArch64_002dDependent.html#AArch64_002dDependent" rel="up" title="AArch64-Dependent">
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<link href="AArch64-Opcodes.html#AArch64-Opcodes" rel="next" title="AArch64 Opcodes">
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<link href="AArch64-Floating-Point.html#AArch64-Floating-Point" rel="prev" title="AArch64 Floating Point">
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</style>
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</head>
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<body lang="en">
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<a name="AArch64-Directives"></a>
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<div class="header">
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<p>
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Next: <a href="AArch64-Opcodes.html#AArch64-Opcodes" accesskey="n" rel="next">AArch64 Opcodes</a>, Previous: <a href="AArch64-Floating-Point.html#AArch64-Floating-Point" accesskey="p" rel="prev">AArch64 Floating Point</a>, Up: <a href="AArch64_002dDependent.html#AArch64_002dDependent" accesskey="u" rel="up">AArch64-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="AArch64-Machine-Directives"></a>
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<h4 class="subsection">9.1.5 AArch64 Machine Directives</h4>
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<a name="index-machine-directives_002c-AArch64"></a>
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<a name="index-AArch64-machine-directives"></a>
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<dl compact="compact">
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<dd>
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<a name="index-_002earch-directive_002c-AArch64"></a>
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</dd>
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<dt><code>.arch <var>name</var></code></dt>
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<dd><p>Select the target architecture. Valid values for <var>name</var> are the same as
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for the <samp>-march</samp> command-line option.
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</p>
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<p>Specifying <code>.arch</code> clears any previously selected architecture
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extensions.
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</p>
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<a name="index-_002earch_005fextension-directive_002c-AArch64"></a>
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</dd>
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<dt><code>.arch_extension <var>name</var></code></dt>
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<dd><p>Add or remove an architecture extension to the target architecture. Valid
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values for <var>name</var> are the same as those accepted as architectural
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extensions by the <samp>-mcpu</samp> command-line option.
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</p>
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<p><code>.arch_extension</code> may be used multiple times to add or remove extensions
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incrementally to the architecture being compiled for.
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</p>
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<a name="index-_002ebss-directive_002c-AArch64"></a>
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</dd>
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<dt><code>.bss</code></dt>
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<dd><p>This directive switches to the <code>.bss</code> section.
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</p>
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<a name="index-_002ecpu-directive_002c-AArch64"></a>
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</dd>
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<dt><code>.cpu <var>name</var></code></dt>
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<dd><p>Set the target processor. Valid values for <var>name</var> are the same as
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those accepted by the <samp>-mcpu=</samp> command-line option.
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</p>
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<a name="index-_002edword-directive_002c-AArch64"></a>
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</dd>
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<dt><code>.dword <var>expressions</var></code></dt>
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<dd><p>The <code>.dword</code> directive produces 64 bit values.
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</p>
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<a name="index-_002eeven-directive_002c-AArch64"></a>
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</dd>
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<dt><code>.even</code></dt>
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<dd><p>The <code>.even</code> directive aligns the output on the next even byte
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boundary.
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</p>
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<a name="index-_002einst-directive_002c-AArch64"></a>
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</dd>
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<dt><code>.inst <var>expressions</var></code></dt>
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<dd><p>Inserts the expressions into the output as if they were instructions,
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rather than data.
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</p>
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<a name="index-_002eltorg-directive_002c-AArch64"></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 into the current section (which is assumed to be the .text
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section) at the current location (aligned to a word boundary).
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GAS maintains a separate literal pool for each section and each
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sub-section. The <code>.ltorg</code> directive will only affect the literal
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pool of the current section and sub-section. At the end of assembly
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all remaining, un-empty literal pools will automatically be dumped.
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</p>
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<p>Note - older versions of GAS would dump the current literal
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pool any time a section change occurred. This is no longer done, since
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it prevents accurate control of the placement of literal pools.
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</p>
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<a name="index-_002epool-directive_002c-AArch64"></a>
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</dd>
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<dt><code>.pool</code></dt>
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<dd><p>This is a synonym for .ltorg.
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</p>
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<a name="index-_002ereq-directive_002c-AArch64"></a>
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</dd>
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<dt><code><var>name</var> .req <var>register name</var></code></dt>
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<dd><p>This creates an alias for <var>register name</var> called <var>name</var>. For
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example:
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</p>
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<div class="smallexample">
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<pre class="smallexample"> foo .req w0
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</pre></div>
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<p>ip0, ip1, lr and fp are automatically defined to
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alias to X16, X17, X30 and X29 respectively.
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</p>
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<a name="index-_002etlsdescadd-directive_002c-AArch64"></a>
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</dd>
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<dt><code><code>.tlsdescadd</code></code></dt>
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<dd><p>Emits a TLSDESC_ADD reloc on the next instruction.
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</p>
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<a name="index-_002etlsdesccall-directive_002c-AArch64"></a>
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</dd>
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<dt><code><code>.tlsdesccall</code></code></dt>
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<dd><p>Emits a TLSDESC_CALL reloc on the next instruction.
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</p>
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<a name="index-_002etlsdescldr-directive_002c-AArch64"></a>
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</dd>
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<dt><code><code>.tlsdescldr</code></code></dt>
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<dd><p>Emits a TLSDESC_LDR reloc on the next instruction.
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</p>
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<a name="index-_002eunreq-directive_002c-AArch64"></a>
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</dd>
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<dt><code>.unreq <var>alias-name</var></code></dt>
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<dd><p>This undefines a register alias which was previously defined using the
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<code>req</code> directive. For example:
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</p>
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<div class="smallexample">
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<pre class="smallexample"> foo .req w0
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.unreq foo
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</pre></div>
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<p>An error occurs if the name is undefined. Note - this pseudo op can
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be used to delete builtin in register name aliases (eg ’w0’). This
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should only be done if it is really necessary.
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</p>
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<a name="index-_002exword-directive_002c-AArch64"></a>
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</dd>
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<dt><code>.xword <var>expressions</var></code></dt>
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<dd><p>The <code>.xword</code> directive produces 64 bit values. This is the same
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as the <code>.dword</code> directive.
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</p>
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<a name="index-_002ecfi_005fb_005fkey_005fframe-directive_002c-AArch64"></a>
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</dd>
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<dt><code><code>.cfi_b_key_frame</code></code></dt>
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<dd><p>The <code>.cfi_b_key_frame</code> directive inserts a ’B’ character into the CIE
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corresponding to the current frame’s FDE, meaning that its return address has
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been signed with the B-key. If two frames are signed with differing keys then
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they will not share the same CIE. This information is intended to be used by
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the stack unwinder in order to properly authenticate return addresses.
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</p>
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</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="AArch64-Opcodes.html#AArch64-Opcodes" accesskey="n" rel="next">AArch64 Opcodes</a>, Previous: <a href="AArch64-Floating-Point.html#AArch64-Floating-Point" accesskey="p" rel="prev">AArch64 Floating Point</a>, Up: <a href="AArch64_002dDependent.html#AArch64_002dDependent" accesskey="u" rel="up">AArch64-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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</body>
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</html>
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