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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Missed range check narrowing opportunity"
href="https://bugs.llvm.org/show_bug.cgi?id=52411">52411</a>
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<th>Summary</th>
<td>Missed range check narrowing opportunity
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
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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
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Scalar Optimizations
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>listmail@philipreames.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>The following transform is not performed in O3 today. Essentially, we end up
performing a redundant extend just to perform a range check. This particular
example has been alive verified, but I have not tried to generalize under what
set of ranges the bitwidth reduction can be done.
define i1 @src(i8 %x) {
%conv28 = zext i8 %x to i32
%isdigittmp = add nsw i32 %conv28, -48
%isdigit = icmp ugt i32 %isdigittmp, 9
ret i1 %isdigit
}
define i1 @tgt(i8 %x) {
%isdigittmp = add i8 %x, -48
%isdigit = icmp ugt i8 %isdigittmp, 9
ret i1 %isdigit
}</pre>
</div>
</p>
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