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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - recognize when switch statement is used to implement goto"
href="https://bugs.llvm.org/show_bug.cgi?id=39043">39043</a>
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<th>Summary</th>
<td>recognize when switch statement is used to implement goto
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
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<th>Version</th>
<td>7.0
</td>
</tr>
<tr>
<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>
<tr>
<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>slandden@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>gcc can correctly optimize this code ( <a href="https://godbolt.org/z/1GEhQV">https://godbolt.org/z/1GEhQV</a> ), but
clang cannot: This optimization is important when using goto to build a state
machine, or in the zig and rust languages, which lack goto. In these languages
goto can be implemented with a switch statement, an enum, and continue, but
only correctly if this optimization is done.
#include <stdbool.h>
#include <stdio.h>
enum states {
one,
two,
three,
};
void gotoexample(unsigned char num) {
enum states state = one;
while (true) {
switch (state) {
case one: {
state = two;
break;
} case two: {
state = three;
break;
} case three: {
puts("foo");
return;
}
}
}
}</pre>
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