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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - @llvm.memcpy not honoring volatile"
href="https://bugs.llvm.org/show_bug.cgi?id=42254">42254</a>
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<th>Summary</th>
<td>@llvm.memcpy not honoring volatile
</td>
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<th>Product</th>
<td>libraries
</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>All
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<th>Status</th>
<td>NEW
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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>Common Code Generator Code
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>gchatelet@google.com
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</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Full discussion here:
<a href="http://lists.llvm.org/pipermail/llvm-dev/2019-June/132808.html">http://lists.llvm.org/pipermail/llvm-dev/2019-June/132808.html</a>
The following IR with the volatile parameter set to true
<span class="quote">> call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 1 %0, i8* align 1 %1, i64</span >
7, i1 true)
generates the following asm:
<span class="quote">> movl (%rsi), %eax
> movl 3(%rsi), %ecx
> movl %ecx, 3(%rdi)
> movl %eax, (%rdi)</span >
It performs an overlapping read/write which - I believe - is violating the
volatile semantic
Full example here: <a href="https://godbolt.org/z/P_rjBT">https://godbolt.org/z/P_rjBT</a></pre>
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