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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - missing optimization of multiply overflow check"
href="https://llvm.org/bugs/show_bug.cgi?id=27794">27794</a>
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<th>Summary</th>
<td>missing optimization of multiply overflow check
</td>
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<th>Product</th>
<td>new-bugs
</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>normal
</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>regehr@cs.utah.edu
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>This is a portable, UB-free idiom for seeing if a multiply is going to
overflow:
int f(unsigned a, unsigned b) { return a > (UINT_MAX / b); }
we should turn this into a multiply with condition code and then also CSE it
with the multiply itself which will surely be nearby.
Request for this optimization comes from Rich Felker, author of Musl libc:
<a href="http://wiki.musl-libc.org/wiki/Projects_using_musl">http://wiki.musl-libc.org/wiki/Projects_using_musl</a>
This should be done in CodeGenPrepare, Sanjoy Das says.</pre>
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