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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 - [Machine Block Placement] wrong code with -force-loop-cold-block"
href="https://bugs.llvm.org/show_bug.cgi?id=48761">48761</a>
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<th>Summary</th>
<td>[Machine Block Placement] wrong code with -force-loop-cold-block
</td>
</tr>
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<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Common Code Generator Code
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>paulsson@linux.vnet.ibm.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=24382" name="attach_24382" title="reduced testcase">attachment 24382</a> <a href="attachment.cgi?id=24382&action=edit" title="reduced testcase">[details]</a></span>
reduced testcase
This program should execute the inner loop in c() once and therefore print '5'.
volatile int a = 0, b = 1;
void c() {
for (; b < 2; b++)
for (; a < 5; a++)
;
}
int main() {
c();
printf("%d\n", a);
}
However, with -force-loop-cold-block, it prints 0, because it moves the outer
latch up to before the outer loop, increments b first, and then directly exits
since b is now 2...
llc -mcpu=arch13 tc.mir -run-pass=block-placement -force-loop-cold-block</pre>
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