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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 - [SLP] getVectorElementSize() is slow"
   href="https://bugs.llvm.org/show_bug.cgi?id=45269">45269</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>[SLP] getVectorElementSize() is slow
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>libraries
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>trunk
          </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>enhancement
          </td>
        </tr>

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

        <tr>
          <th>Component</th>
          <td>Scalar Optimizations
          </td>
        </tr>

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

        <tr>
          <th>Reporter</th>
          <td>nikita.ppv@gmail.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Compiling shared_sha256.c from test-suite:

clang -DNDEBUG  -O3   -w -Werror=date-time -save-stats=obj -DHAVE_CONFIG_H
-I/home/nikic/llvm-test-suite/MultiSource/Applications/ClamAV
-I/home/nikic/llvm-test-suite/MultiSource/Applications/ClamAV/zlib
-DDONT_LOCK_DBDIRS -DC_LINUX -DFPU_WORDS_BIGENDIAN=0 -DWORDS_BIGENDIAN=0
-save-stats=obj -MD -MT
MultiSource/Applications/ClamAV/CMakeFiles/clamscan.dir/shared_sha256.c.o -MF
MultiSource/Applications/ClamAV/CMakeFiles/clamscan.dir/shared_sha256.c.o.d -o
MultiSource/Applications/ClamAV/CMakeFiles/clamscan.dir/shared_sha256.c.o   -c
../MultiSource/Applications/ClamAV/shared_sha256.c

50% of the time is taken up by SLP vectorization, with 35% inside
getVectorElementSize().

The function for reference:
<a href="https://github.com/llvm/llvm-project/blob/601d25cb736d8b67e642faa06f9e956c67fd25d9/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp#L5299">https://github.com/llvm/llvm-project/blob/601d25cb736d8b67e642faa06f9e956c67fd25d9/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp#L5299</a>

It performs a full instruction scan starting from a root, which may end up
visiting a very large number of instructions.

Is it possible to limit this walk in some way?</pre>
        </div>
      </p>


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