<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 --- - Wrong constant folding"
   href="http://llvm.org/bugs/show_bug.cgi?id=15959">15959</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Wrong constant folding
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>clang
          </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>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>ishiura-compiler@ml.kwansei.ac.jp
          </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>LLVM (git) + clang (3.4) for x86_64 miscompiles the following code.

    $ cat error.c

    int main (void)
    {
      volatile short x = 1;
      static long k = 1L;
      int a = x << ( k - 1 );   // a = 1
      long t = 1L >> a ;        // t = 0
      if ( t != 0L ) { __builtin_abort(); }
      return 0;
    }

    $ clang error.c -O1
    $ ./a.out
    Aborted (core dumped)

The following code with variable k replaced by "1L" is
correctly compiled.

    $ cat noerror.c

    int main (void)
    {
      volatile short x = 1;
      int a = x << ( 1L - 1 );  // a = 1
      long t = 1L >> a ;        // t = 0
      if ( t != 0L ) { __builtin_abort(); }
      return 0;
    }

    $ clang noerror.c -O1
    $ ./a.out
    $ echo $?
    0

    $ clang -v
    clang version 3.4 (<a href="http://llvm.org/git/clang.git">http://llvm.org/git/clang.git</a>
dd256314cf391063329e504f0ece46ee51bbfa2a) (<a href="http://llvm.org/git/llvm.git">http://llvm.org/git/llvm.git</a>
51dab6e3945a6d06a713869967ced3a8f9fb6294)
    Target: x86_64-unknown-linux-gnu
    Thread model: posix</pre>
        </div>
      </p>
      <hr>
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