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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Regression in StructurizeCFG, r321751: complex loop structure turned into infinite loop"
href="https://bugs.llvm.org/show_bug.cgi?id=36015">36015</a>
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<th>Summary</th>
<td>Regression in StructurizeCFG, r321751: complex loop structure turned into infinite loop
</td>
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<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
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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>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Scalar Optimizations
</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>nhaehnle@gmail.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=19710" name="attach_19710" title="Reduced test case">attachment 19710</a> <a href="attachment.cgi?id=19710&action=edit" title="Reduced test case">[details]</a></span>
Reduced test case
I'm attaching a reduced test case, plus the output of `opt -structurizecfg`.
Change r321751 ("StructurizeCFG: Fix broken backedge detection") breaks this
test case, in the following way:
The original code has edges from both %if and %else into the %exit block. In
the resulting code, the edge from %if to %exit disappears: if the exit
condition is met (%cond.if = false), the control will follow %if -> %Flow1 ->
%Flow2 -> %loop.outer instead of %if -> %Flow1 -> %Flow2 -> %exit.
This bug regresses various OpenGL test suites, for example
dEQP-GLES3.functional.shaders.loops.do_while_dynamic_iterations.conditional_continue_vertex.</pre>
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