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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - atomic_signal_fence should not generate a dmb on aarch64"
href="https://bugs.llvm.org/show_bug.cgi?id=50564">50564</a>
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<th>Summary</th>
<td>atomic_signal_fence should not generate a dmb on aarch64
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<th>Product</th>
<td>new-bugs
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<th>Version</th>
<td>11.0
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<th>Hardware</th>
<td>Macintosh
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<th>OS</th>
<td>MacOS X
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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>new bugs
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>saagar@saagarjha.com
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<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
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<pre>This is related to <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - atomic_signal_fence generates a dmb instruction on aarch64 and arm"
href="show_bug.cgi?id=27545">https://bugs.llvm.org/show_bug.cgi?id=27545</a>, which is
fixed–but apparently only for optimized code. Without optimization I'm still
seeing a dmb ish for atomic_signal_fence on aarch64. The standard (7.17.4.2)
specifically mentions that "hardware fence instructions that
atomic_thread_fence would have inserted are not emitted", so this I think this
behavior is somewhat surprising if not incorrect. Here's a Godbolt link with
sample code compiled without optimization demonstrating this bug:
<a href="https://godbolt.org/z/qh55n184G">https://godbolt.org/z/qh55n184G</a></pre>
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