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| <h4 class="subsection">9.1.5 AArch64 Machine Directives</h4> |
| |
| <p><a name="index-machine-directives_002c-AArch64-563"></a><a name="index-AArch64-machine-directives-564"></a> |
| <dl> |
| <!-- AAAAAAAAAAAAAAAAAAAAAAAAA --> |
| |
| <p><a name="index-g_t_0040code_007b_002earch_007d-directive_002c-AArch64-565"></a><dt><code>.arch </code><var>name</var><dd>Select the target architecture. Valid values for <var>name</var> are the same as |
| for the <samp><span class="option">-march</span></samp> command-line option. |
| |
| <p>Specifying <code>.arch</code> clears any previously selected architecture |
| extensions. |
| |
| <p><a name="index-g_t_0040code_007b_002earch_005fextension_007d-directive_002c-AArch64-566"></a><br><dt><code>.arch_extension </code><var>name</var><dd>Add or remove an architecture extension to the target architecture. Valid |
| values for <var>name</var> are the same as those accepted as architectural |
| extensions by the <samp><span class="option">-mcpu</span></samp> command-line option. |
| |
| <p><code>.arch_extension</code> may be used multiple times to add or remove extensions |
| incrementally to the architecture being compiled for. |
| |
| <!-- BBBBBBBBBBBBBBBBBBBBBBBBBB --> |
| <p><a name="index-g_t_0040code_007b_002ebss_007d-directive_002c-AArch64-567"></a><br><dt><code>.bss</code><dd>This directive switches to the <code>.bss</code> section. |
| |
| <!-- CCCCCCCCCCCCCCCCCCCCCCCCCC --> |
| <p><a name="index-g_t_0040code_007b_002ecpu_007d-directive_002c-AArch64-568"></a><br><dt><code>.cpu </code><var>name</var><dd>Set the target processor. Valid values for <var>name</var> are the same as |
| those accepted by the <samp><span class="option">-mcpu=</span></samp> command-line option. |
| |
| <!-- DDDDDDDDDDDDDDDDDDDDDDDDDD --> |
| <p><a name="index-g_t_0040code_007b_002edword_007d-directive_002c-AArch64-569"></a><br><dt><code>.dword </code><var>expressions</var><dd>The <code>.dword</code> directive produces 64 bit values. |
| |
| <!-- EEEEEEEEEEEEEEEEEEEEEEEEEE --> |
| <p><a name="index-g_t_0040code_007b_002eeven_007d-directive_002c-AArch64-570"></a><br><dt><code>.even</code><dd>The <code>.even</code> directive aligns the output on the next even byte |
| boundary. |
| |
| <!-- FFFFFFFFFFFFFFFFFFFFFFFFFF --> |
| <p><a name="index-g_t_0040code_007b_002efloat16_007d-directive_002c-AArch64-571"></a><br><dt><code>.float16 </code><var>value [,...,value_n]</var><dd>Place the half precision floating point representation of one or more |
| floating-point values into the current section. |
| The format used to encode the floating point values is always the |
| IEEE 754-2008 half precision floating point format. |
| |
| <!-- GGGGGGGGGGGGGGGGGGGGGGGGGG --> |
| <!-- HHHHHHHHHHHHHHHHHHHHHHHHHH --> |
| <!-- IIIIIIIIIIIIIIIIIIIIIIIIII --> |
| <p><a name="index-g_t_0040code_007b_002einst_007d-directive_002c-AArch64-572"></a><br><dt><code>.inst </code><var>expressions</var><dd>Inserts the expressions into the output as if they were instructions, |
| rather than data. |
| |
| <!-- JJJJJJJJJJJJJJJJJJJJJJJJJJ --> |
| <!-- KKKKKKKKKKKKKKKKKKKKKKKKKK --> |
| <!-- LLLLLLLLLLLLLLLLLLLLLLLLLL --> |
| <p><a name="index-g_t_0040code_007b_002eltorg_007d-directive_002c-AArch64-573"></a><br><dt><code>.ltorg</code><dd>This directive causes the current contents of the literal pool to be |
| dumped into the current section (which is assumed to be the .text |
| section) at the current location (aligned to a word boundary). |
| GAS maintains a separate literal pool for each section and each |
| sub-section. The <code>.ltorg</code> directive will only affect the literal |
| pool of the current section and sub-section. At the end of assembly |
| all remaining, un-empty literal pools will automatically be dumped. |
| |
| <p>Note - older versions of GAS would dump the current literal |
| pool any time a section change occurred. This is no longer done, since |
| it prevents accurate control of the placement of literal pools. |
| |
| <!-- MMMMMMMMMMMMMMMMMMMMMMMMMM --> |
| <!-- NNNNNNNNNNNNNNNNNNNNNNNNNN --> |
| <!-- OOOOOOOOOOOOOOOOOOOOOOOOOO --> |
| <!-- PPPPPPPPPPPPPPPPPPPPPPPPPP --> |
| <p><a name="index-g_t_0040code_007b_002epool_007d-directive_002c-AArch64-574"></a><br><dt><code>.pool</code><dd>This is a synonym for .ltorg. |
| |
| <!-- QQQQQQQQQQQQQQQQQQQQQQQQQQ --> |
| <!-- RRRRRRRRRRRRRRRRRRRRRRRRRR --> |
| <p><a name="index-g_t_0040code_007b_002ereq_007d-directive_002c-AArch64-575"></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 |
| example: |
| |
| <pre class="smallexample"> foo .req w0 |
| </pre> |
| <p>ip0, ip1, lr and fp are automatically defined to |
| alias to X16, X17, X30 and X29 respectively. |
| |
| <!-- SSSSSSSSSSSSSSSSSSSSSSSSSS --> |
| <!-- TTTTTTTTTTTTTTTTTTTTTTTTTT --> |
| <p><a name="index-g_t_0040code_007b_002etlsdescadd_007d-directive_002c-AArch64-576"></a><br><dt><code>.tlsdescadd</code><dd>Emits a TLSDESC_ADD reloc on the next instruction. |
| |
| <p><a name="index-g_t_0040code_007b_002etlsdesccall_007d-directive_002c-AArch64-577"></a><br><dt><code>.tlsdesccall</code><dd>Emits a TLSDESC_CALL reloc on the next instruction. |
| |
| <p><a name="index-g_t_0040code_007b_002etlsdescldr_007d-directive_002c-AArch64-578"></a><br><dt><code>.tlsdescldr</code><dd>Emits a TLSDESC_LDR reloc on the next instruction. |
| |
| <!-- UUUUUUUUUUUUUUUUUUUUUUUUUU --> |
| <p><a name="index-g_t_0040code_007b_002eunreq_007d-directive_002c-AArch64-579"></a><br><dt><code>.unreq </code><var>alias-name</var><dd>This undefines a register alias which was previously defined using the |
| <code>req</code> directive. For example: |
| |
| <pre class="smallexample"> foo .req w0 |
| .unreq foo |
| </pre> |
| <p>An error occurs if the name is undefined. Note - this pseudo op can |
| be used to delete builtin in register name aliases (eg 'w0'). This |
| should only be done if it is really necessary. |
| |
| <!-- VVVVVVVVVVVVVVVVVVVVVVVVVV --> |
| <p><a name="index-g_t_0040code_007b_002evariant_005fpcs_007d-directive_002c-AArch64-580"></a><br><dt><code>.variant_pcs </code><var>symbol</var><dd>This directive marks <var>symbol</var> referencing a function that may |
| follow a variant procedure call standard with different register |
| usage convention from the base procedure call standard. |
| |
| <!-- WWWWWWWWWWWWWWWWWWWWWWWWWW --> |
| <!-- XXXXXXXXXXXXXXXXXXXXXXXXXX --> |
| <p><a name="index-g_t_0040code_007b_002exword_007d-directive_002c-AArch64-581"></a><br><dt><code>.xword </code><var>expressions</var><dd>The <code>.xword</code> directive produces 64 bit values. This is the same |
| as the <code>.dword</code> directive. |
| |
| <!-- YYYYYYYYYYYYYYYYYYYYYYYYYY --> |
| <!-- ZZZZZZZZZZZZZZZZZZZZZZZZZZ --> |
| <p><a name="index-g_t_0040code_007b_002ecfi_005fb_005fkey_005fframe_007d-directive_002c-AArch64-582"></a><br><dt><code>.cfi_b_key_frame</code><dd>The <code>.cfi_b_key_frame</code> directive inserts a 'B' character into the CIE |
| corresponding to the current frame's FDE, meaning that its return address has |
| been signed with the B-key. If two frames are signed with differing keys then |
| they will not share the same CIE. This information is intended to be used by |
| the stack unwinder in order to properly authenticate return addresses. |
| |
| </dl> |
| |
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