<html>
    <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 --- - crash on valid code at -O1 and above in 64-bit mode on x86_64-linux-gnu (error in backend: Broken function found)"
   href="https://llvm.org/bugs/show_bug.cgi?id=26973">26973</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>crash on valid code at -O1 and above in 64-bit mode on x86_64-linux-gnu (error in backend: Broken function found)
          </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>Windows NT
          </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>unassignedclangbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>chengniansun@gmail.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>The following code crashes clang trunk at -O1 and above in 64-bit mode on
x86_64-linux-gnu.  


$: clang-trunk -v
clang version 3.9.0 (trunk 263641)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5.3.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9.2
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.3.0
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64
$: 
$: clang-trunk -w -c small.c -O1
Instruction does not dominate all uses!
  %dec3 = add nsw i32 %p1.addr.0, -1
  %3 = sext i32 %dec3 to i64
fatal error: error in backend: Broken function found, compilation aborted!
clang-3.9: error: clang frontend command failed with exit code 70 (use -v to
see invocation)
clang version 3.9.0 (trunk 263641)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/bin
clang-3.9: note: diagnostic msg: PLEASE submit a bug report to
<a href="http://llvm.org/bugs/">http://llvm.org/bugs/</a> and include the crash backtrace, preprocessed source, and
associated run script.
clang-3.9: note: diagnostic msg: 
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang-3.9: note: diagnostic msg: /home/cnsun/ramdisk/tmp/small-04eb97.c
clang-3.9: note: diagnostic msg: /home/cnsun/ramdisk/tmp/small-04eb97.sh
clang-3.9: note: diagnostic msg: 

********************
$: 
$: clang-trunk -w -c small.c -O0
$: 
$: cat small.c
int a;
double b;
double *c;
void fn1(p1) {
  for (;; p1--) {
    a = p1;
    for (; p1 >= a; a--)
      b = c[p1];
  }
}
$:</pre>
        </div>
      </p>
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