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      <base href="https://bugs.llvm.org/">
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    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - Loop-Interchange crashes if the first phi node of a header is not an induction node"
   href="https://bugs.llvm.org/show_bug.cgi?id=48212">48212</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Loop-Interchange crashes if the first phi node of a header is not an induction node
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>tools
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>11.0
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Linux
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>opt
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>flemairen6@gmail.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Created <span class=""><a href="attachment.cgi?id=24179" name="attach_24179" title="IR file that causes the crash to happen.">attachment 24179</a> <a href="attachment.cgi?id=24179&action=edit" title="IR file that causes the crash to happen.">[details]</a></span>
IR file that causes the crash to happen.

$ clang test.c -Xclang -disable-O0-optnone -emit-llvm -O0 -S -o test.ll
$ opt -mem2reg -loop-rotate -loop-interchange test.ll

opt: llvm-project/llvm/lib/Transforms/Scalar/LoopInterchange.cpp:1583: bool
(anonymous namespace)::LoopInterchangeTransform::adjustLoopBranches():
Assertion `OuterInnerReductions.find(PHI) != OuterInnerReductions.end() &&
"Expected a reduction PHI node"' failed.

And then there is the stacktrace. 

test.c : 

void foo (int filter[5][5]){
    int k1, k2;
    int temp, mul;
    L1:for (k1=0;k1<5;k1++){
        L2:for (k2=0;k2<3;k2++){
           mul = filter[k2][k1];
           temp += mul;
        }
    }
}

int main() {
  int filter[5][5];
  foo(filter);
}

Build :

LLVM (<a href="http://llvm.org/">http://llvm.org/</a>):
  LLVM version 11.0.0git
  DEBUG build with assertions.
  Default target: x86_64-unknown-linux-gnu
  Host CPU: skylake</pre>
        </div>
      </p>


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