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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - -GS stack buffer checks are expensive"
href="https://bugs.llvm.org/show_bug.cgi?id=38679">38679</a>
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<th>Summary</th>
<td>-GS stack buffer checks are expensive
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>unspecified
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Windows NT
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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>-New Bugs
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>dmajor@mozilla.com
</td>
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<th>CC</th>
<td>froydnj@gmail.com, hans@chromium.org, llvm-bugs@lists.llvm.org, rnk@google.com
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<pre>We recently observed that compiling Firefox with `-GS-` gives a 4-6%
improvement to our perf test suite in clang-cl builds. Adding the same flag to
MSVC builds gives a <1% improvement if anything.
Is there anything that can be done to improve clang's implementation? I found
this review (a bit old, not sure if it's still relevant)
<a href="https://reviews.llvm.org/D20346">https://reviews.llvm.org/D20346</a> that says "I think we can look into situations
where Clang emits stack guards and MSVC doesn't if that turns out to be a
problem later."
As a first guess:
<a href="https://msdn.microsoft.com/en-us/library/8dbf701c.aspx#Anchor_3">https://msdn.microsoft.com/en-us/library/8dbf701c.aspx#Anchor_3</a> describes some
limitations on the buffers that MSVC checks. I wonder if clang that into
account?</pre>
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