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    <head>
      <base href="https://bugs.llvm.org/">
    </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 - Failure to optimize out useless zero-ing after register was already zero-ed"
   href="https://bugs.llvm.org/show_bug.cgi?id=45723">45723</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Failure to optimize out useless zero-ing after register was already zero-ed
          </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>Backend: X86
          </td>
        </tr>

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

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

        <tr>
          <th>CC</th>
          <td>craig.topper@gmail.com, llvm-bugs@lists.llvm.org, llvm-dev@redking.me.uk, spatel+llvm@rotateright.com
          </td>
        </tr></table>
      <p>
        <div>
        <pre>int f(bool b, int *p)
{
    return b && *p;
}

LLVM generates this with -O3 : 

f(bool, int*): # @f(bool, int*)
  xor eax, eax ; Note that eax is zero-ed here
  test dil, dil
  je .LBB0_2
  xor eax, eax ; Zero-ing eax here is thus useless
  cmp dword ptr [rsi], 0
  setne al
.LBB0_2:
  ret</pre>
        </div>
      </p>


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