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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - support for `.arch_extension rcpc`"
href="https://bugs.llvm.org/show_bug.cgi?id=46674">46674</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>support for `.arch_extension rcpc`
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>All
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Backend: AArch64
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>ndesaulniers@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>arnaud.degrandmaison@arm.com, caij2003@gmail.com, daniel.kiss@arm.com, llozano@chromium.org, llvm-bugs@lists.llvm.org, oliver.stannard@arm.com, smithp352@googlemail.com, srhines@google.com, t.p.northover@gmail.com, Ties.Stuij@arm.com
</td>
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<th>Blocks</th>
<td>4068
</td>
</tr></table>
<p>
<div>
<pre>Proposed kernel patch [0] looks to make use of `rcpc` ARMv8.3 extension [1].
It uses feature detection at build time to see if the assembler supports the
following assembler directive:
$ clang -x assembler --target=aarch64-linux-gnu -march=armv8.3a <(echo
".arch_extension rcpc")
I've tried:
* -march=armv8.3a
* -mcpu=cortex-a77+rcpc
* -mcpu=neoverse-e1
* -mcpu=neoverse-n1
But all of them report:
/proc/self/fd/11:1:17: error: unknown architectural extension: rcpc
.arch_extension rcpc
^
Looking into llvm unit tests, I don't see any tests that actually test the
assembler for `.arch_extension rcpc`.
[0] <a href="https://lore.kernel.org/lkml/20200710165203.31284-18-will@kernel.org/T/#u">https://lore.kernel.org/lkml/20200710165203.31284-18-will@kernel.org/T/#u</a>
[1]
<a href="https://sourceware.org/binutils/docs/as/AArch64-Extensions.html#AArch64-Extensions">https://sourceware.org/binutils/docs/as/AArch64-Extensions.html#AArch64-Extensions</a></pre>
</div>
</p>
<div id="referenced">
<hr style="border: 1px dashed #969696">
<b>Referenced Bugs:</b>
<ul>
<li>
[<a class="bz_bug_link
bz_status_CONFIRMED "
title="CONFIRMED - [Meta] Compiling the Linux kernel with clang"
href="https://bugs.llvm.org/show_bug.cgi?id=4068">Bug 4068</a>] [Meta] Compiling the Linux kernel with clang
</li>
</ul>
</div>
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