<html>
    <head>
      <base href="http://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 --- - Performance regression when LTO is enabled"
   href="http://llvm.org/bugs/show_bug.cgi?id=20004">20004</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Performance regression when LTO is enabled
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>clang
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>3.4
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>Macintosh
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>MacOS X
          </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>LLVM Codegen
          </td>
        </tr>

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

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

        <tr>
          <th>CC</th>
          <td>llvmbugs@cs.uiuc.edu
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Without LTO:

clang PerformanceTest.cpp dsp.cpp -std=c++11 -ffast-math -O3 -o PerformanceTest

Apple LLVM version 5.1 (clang-503.0.40) (based on LLVM 3.4svn)
Target: x86_64-apple-darwin13.2.0
Thread model: posix

Iterations: 955
C results: 100,043,846 shorts per second.

With LTO:

clang PerformanceTest.cpp dsp.cpp -std=c++11 -ffast-math -flto -O3 -o
PerformanceTest

Apple LLVM version 5.1 (clang-503.0.40) (based on LLVM 3.4svn)
Target: x86_64-apple-darwin13.2.0
Thread model: posix

Iterations: 586
C results: 61,349,033 shorts per second.

Code can be downloaded from here:
<a href="https://gist.github.com/learnopengles/004ff4eee75057ca006c">https://gist.github.com/learnopengles/004ff4eee75057ca006c</a></pre>
        </div>
      </p>
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