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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 - Missing fold trunc(ctlz(zext(x))) -> add(ctlz(x), C)"
href="https://bugs.llvm.org/show_bug.cgi?id=50173">50173</a>
</td>
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<tr>
<th>Summary</th>
<td>Missing fold trunc(ctlz(zext(x))) -> add(ctlz(x), C)
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Scalar Optimizations
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>david.bolvansky@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>define i16 @src(i16 %x) {
%z = zext i16 %x to i32
%p = call i32 @llvm.ctlz.i32(i32 %z, i1 false)
%zz = trunc i32 %p to i16
ret i16 %zz
}
define i16 @tgt(i16 %x) {
%p = call i16 @llvm.ctlz.i16(i16 %x, i1 false)
%z = add i16 %p, 16
ret i16 %z
}
declare i32 @llvm.ctlz.i32(i32, i1)
declare i16 @llvm.ctlz.i16(i16, i1)
----------------------------------------
define i16 @src(i16 %x) {
%0:
%z = zext i16 %x to i32
%p = ctlz i32 %z, 0
%zz = trunc i32 %p to i16
ret i16 %zz
}
=>
define i16 @tgt(i16 %x) {
%0:
%p = ctlz i16 %x, 0
%z = add i16 %p, 16
ret i16 %z
}
Transformation seems to be correct!</pre>
</div>
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