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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Clang ignores -march when targeting armv7-apple-darwin"
href="https://bugs.llvm.org/show_bug.cgi?id=49293">49293</a>
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<th>Summary</th>
<td>Clang ignores -march when targeting armv7-apple-darwin
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Driver
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>orivej@gmx.fr
</td>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<p>
<div>
<pre>This is a low priority bug since it affects only old hardware targets,
but since it exists in the codebase and I've stumbled upon it I'll
report it.
When running "clang --target=armv7-apple-darwin14 -march=armv8.2-a+dotprod"
MachO::TranslateArgs is called with BoundArch "armv7" and appends
"-march=armv7a" to the list of the command line args:
<a href="https://github.com/llvm/llvm-project/blob/llvmorg-13-init/clang/lib/Driver/ToolChains/Darwin.cpp#L2380">https://github.com/llvm/llvm-project/blob/llvmorg-13-init/clang/lib/Driver/ToolChains/Darwin.cpp#L2380</a>
Then clang -cc1 uses it, silently ignoring the custom -march.
The same issue was encountered in
<a href="https://github.com/tensorflow/tensorflow/issues/40026">https://github.com/tensorflow/tensorflow/issues/40026</a>
and worker around in <a href="https://github.com/google/XNNPACK/pull/692/files">https://github.com/google/XNNPACK/pull/692/files</a>
by adding -mcpu to the command line. (In my case the workaround would
be "-mcpu=cyclone+dotprod".)</pre>
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