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<title>AArch64 Directives - Using as</title>
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<a name="AArch64-Directives"></a>
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Next: <a rel="next" accesskey="n" href="AArch64-Opcodes.html#AArch64-Opcodes">AArch64 Opcodes</a>,
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Previous: <a rel="previous" accesskey="p" href="AArch64-Floating-Point.html#AArch64-Floating-Point">AArch64 Floating Point</a>,
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Up: <a rel="up" accesskey="u" href="AArch64_002dDependent.html#AArch64_002dDependent">AArch64-Dependent</a>
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<h4 class="subsection">9.1.5 AArch64 Machine Directives</h4>
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<p><a name="index-machine-directives_002c-AArch64-547"></a><a name="index-AArch64-machine-directives-548"></a>
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<dl>
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<!-- AAAAAAAAAAAAAAAAAAAAAAAAA -->
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<p><a name="index-g_t_0040code_007b_002earch_007d-directive_002c-AArch64-549"></a><dt><code>.arch </code><var>name</var><dd>Select the target architecture. Valid values for <var>name</var> are the same as
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for the <samp><span class="option">-march</span></samp> commandline option.
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<p>Specifying <code>.arch</code> clears any previously selected architecture
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extensions.
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<p><a name="index-g_t_0040code_007b_002earch_005fextension_007d-directive_002c-AArch64-550"></a><br><dt><code>.arch_extension </code><var>name</var><dd>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><span class="option">-mcpu</span></samp> commandline option.
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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><a name="index-g_t_0040code_007b_002ebss_007d-directive_002c-AArch64-551"></a><br><dt><code>.bss</code><dd>This directive switches to the <code>.bss</code> section.
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<p><a name="index-g_t_0040code_007b_002eltorg_007d-directive_002c-AArch64-552"></a><br><dt><code>.ltorg</code><dd>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>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><a name="index-g_t_0040code_007b_002epool_007d-directive_002c-AArch64-553"></a><br><dt><code>.pool</code><dd>This is a synonym for .ltorg.
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<p><a name="index-g_t_0040code_007b_002ereq_007d-directive_002c-AArch64-554"></a><br><dt><var>name</var><code> .req </code><var>register name</var><dd>This creates an alias for <var>register name</var> called <var>name</var>. For
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example:
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<pre class="smallexample"> foo .req w0
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</pre>
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<p><a name="index-g_t_0040code_007b_002eunreq_007d-directive_002c-AArch64-555"></a><br><dt><code>.unreq </code><var>alias-name</var><dd>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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<pre class="smallexample"> foo .req w0
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.unreq foo
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</pre>
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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><a name="index-g_t_0040code_007b_002exword_007d-directive_002c-AArch64-556"></a><br><dt><code>.xword</code><dd>The <code>.xword</code> directive produces 64 bit values.
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</dl>
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