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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - switch is not converted into an argument LUT when a call return value is discarded"
href="https://bugs.llvm.org/show_bug.cgi?id=41259">41259</a>
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<th>Summary</th>
<td>switch is not converted into an argument LUT when a call return value is discarded
</td>
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<th>Product</th>
<td>new-bugs
</td>
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<th>Version</th>
<td>7.0
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Windows NT
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Keywords</th>
<td>code-quality
</td>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>new bugs
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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</tr>
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<th>Reporter</th>
<td>nok.raven@gmail.com
</td>
</tr>
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<th>CC</th>
<td>hans@chromium.org, htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
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<p>
<div>
<pre>For this code an argument LUT is constructed
int f(int);
int foo(int x)
{
switch (x) {
case 0: return f(12);
case 1: return f(34);
case 2: return f(56);
case 3: return f(78);
case 4: return f(90);
}
}
But if the return value is discarded, as Hans Wennborg noticed in
<a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - jump table switch also contains a branch (conditional jump to a first case)"
href="show_bug.cgi?id=41242#c4">https://bugs.llvm.org/show_bug.cgi?id=41242#c4</a>
int f(int);
int foo(int x)
{
switch (x) {
case 0: f(12); break;
case 1: f(34); break;
case 2: f(56); break;
case 3: f(78); break;
case 4: f(90); break;
}
}
The optimization did not work, and jump table is produced, while it could just
make a call instead of a jump.</pre>
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