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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 - Loop splitting based on monotonic condition between indvar and trip count"
href="https://bugs.llvm.org/show_bug.cgi?id=43910">43910</a>
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<th>Summary</th>
<td>Loop splitting based on monotonic condition between indvar and trip count
</td>
</tr>
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<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<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>Loop Optimizer
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>lebedev.ri@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
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<pre>We could have something like:
void body();
void mainwork();
void remainder();
void bad(unsigned width) {
for(int col = 0; col < width; ++col) {
if(col >= (width - (width % 8))) // last 'width % 8' pixels.
remainder();
else
mainwork();
body();
}
}
Currently that loop is left as-is.
But it could be split into something like this, thus removing conditional from
loop.
void body();
void mainwork();
void remainder();
void good(unsigned width) {
for(int col = 0; col < (width - (width % 8)); ++col) {
if(false /*col >= (width - (width % 8))*/) // last 'width % 8' pixels.
remainder();
else
mainwork();
body();
}
for(int col = (width - (width % 8)); col < width; ++col) {
if(true /*col >= (width - (width % 8))*/) // last 'width % 8' pixels.
remainder();
else
mainwork();
body();
}
}
<a href="https://godbolt.org/z/SVWuJV">https://godbolt.org/z/SVWuJV</a></pre>
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