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    <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 --- - Assertion failed: ((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"), function computeKnownBits, file lib/Analysis/ValueTracking.cpp, line 1606."
   href="https://llvm.org/bugs/show_bug.cgi?id=31809">31809</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Assertion failed: ((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"), function computeKnownBits, file lib/Analysis/ValueTracking.cpp, line 1606.
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>new-bugs
          </td>
        </tr>

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

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

        <tr>
          <th>OS</th>
          <td>All
          </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>new bugs
          </td>
        </tr>

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

        <tr>
          <th>Reporter</th>
          <td>dimitry@andric.com
          </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>From <a href="https://bugs.freebsd.org/216614">https://bugs.freebsd.org/216614</a>, building recent versions of emacs with
recent clang can fail with an assertion:

Assertion failed: ((KnownZero & KnownOne) == 0 && "Bits known to be one AND
zero?"), function computeKnownBits, file lib/Analysis/ValueTracking.cpp, line
1606.

Reduced test case, reproduces with trunk r293557:

/* clang -cc1 -triple x86_64 -S -O2 testcase.c */
enum { x0, x1 } x2(long x3, x4) { return __builtin_assume_aligned(x3 - x4, 8);
}
x5(void *x3) { return x3; }
union x6 {
  int x7
} x8() {
  long x9 = x5(&(union x6){});
  x2(x9, x1);
}

This started to appear somewhere between r282311 and r289043, no narrower
window yet.</pre>
        </div>
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