<html>
    <head>
      <base href="https://llvm.org/bugs/" />
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - [Polly] Make reduction dependency computation work on schedule trees"
   href="https://llvm.org/bugs/show_bug.cgi?id=26320">26320</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>[Polly] Make reduction dependency computation work on schedule trees
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>Polly
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>unspecified
          </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>Optimizer
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>polly-dev@googlegroups.com
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>tobias@grosser.es
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr></table>
      <p>
        <div>
        <pre>When introducing reductions into Polly we thought it would be a good idea to
model reduction dependences using a "convex_hull" computation. However, this is
both computationally a lot more complex than expected and also conflicts made
it hard to compute reduction dependences on schedule trees. Fortunately, Sven
Verdoolaege suggested (at least parts) of what looks like a good solution.
Instead of first computing precise dependences and _then_ reintroducing
reduction dependences, we could just model reduction statements as may-writes
which will make the dependence analysis automatically introduce the additional
dependences needed when removing the inter-reduction-operation dependences.

This blocks <a href="http://reviews.llvm.org/D5190">http://reviews.llvm.org/D5190</a>

This is just a brief reminder. Please ping back in case you need more
information.</pre>
        </div>
      </p>
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