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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 - Clang miscompiles with optimization level -O1 and higher"
   href="https://bugs.llvm.org/show_bug.cgi?id=37667">37667</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Clang miscompiles with optimization level -O1 and higher
          </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>enhancement
          </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>Vsevolod.Livinskij@frtk.ru
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Clang miscompiles with optimization level -O1 and higher.
opt-bisect-limit points to X86 DAG->DAG Instruction Selection on function

Reproducer:
<span class="quote">>$ cat repr.c</span >
#include <stdio.h>

int a, b = 918, c;
unsigned d = 8089;

void foo() {
      a = (unsigned char)(c | b % d);
}

int main() {
  foo();
  printf("%d\n", a);
}

Error:
<span class="quote">>$ clang -O0 repr.c ; ./a.out</span >
150
<span class="quote">>$ clang -O1 repr.c ; ./a.out</span >
918

LLVM version:
clang version 7.0.0 (trunk 333836)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /llvm/bin-trunk/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/4.4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/4.8.2
Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/4.8.5
Selected GCC installation: /usr/lib/gcc/x86_64-redhat-linux/4.8.5
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64</pre>
        </div>
      </p>


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