<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 --- - opt crashes with "opt -loop-rotate -licm -loop-unroll -loop-vectorize": Assertion `Headers.size() >= 2 && "Expected irreducible CFG; -loop-info is likely invalid"' failed"
   href="https://llvm.org/bugs/show_bug.cgi?id=31186">31186</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>opt crashes with "opt -loop-rotate -licm -loop-unroll -loop-vectorize": Assertion `Headers.size() >= 2 && "Expected irreducible CFG; -loop-info is likely invalid"' failed
          </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>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>Scalar Optimizations
          </td>
        </tr>

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

        <tr>
          <th>Reporter</th>
          <td>su@cs.ucdavis.edu
          </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>$ clang -v
clang version 4.0.0 (trunk 287975)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/clang-trunk/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.9.4
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5.3.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7.3
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/4.9.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.3.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.2.0
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64

$ clang -c -emit-llvm -o small.bc small.c
$ opt -loop-rotate -licm -loop-unroll -loop-vectorize -o small-opt.bc small.bc
opt:
/tmp/llvm-builder/llvm-source-trunk/lib/Analysis/BlockFrequencyInfoImpl.cpp:670:
void findIrreducibleHeaders(const llvm::BlockFrequencyInfoImplBase&, const
llvm::bfi_detail::IrreducibleGraph&, const std::vector<const
llvm::bfi_detail::IrreducibleGraph::IrrNode*>&,
llvm::BlockFrequencyInfoImplBase::LoopData::NodeList&,
llvm::BlockFrequencyInfoImplBase::LoopData::NodeList&): Assertion
`Headers.size() >= 2 && "Expected irreducible CFG; -loop-info is likely
invalid"' failed.
#0 0x0000000001c45a45 (opt+0x1c45a45)
#1 0x0000000001c43b2e (opt+0x1c43b2e)
#2 0x0000000001c43c90 (opt+0x1c43c90)
#3 0x00007fce8a932330 __restore_rt
(/lib/x86_64-linux-gnu/libpthread.so.0+0x10330)
#4 0x00007fce8971ec37 gsignal
/build/eglibc-oGUzwX/eglibc-2.19/signal/../nptl/sysdeps/unix/sysv/linux/raise.c:56:0
#5 0x00007fce89722028 abort
/build/eglibc-oGUzwX/eglibc-2.19/stdlib/abort.c:91:0
#6 0x00007fce89717bf6 __assert_fail_base
/build/eglibc-oGUzwX/eglibc-2.19/assert/assert.c:92:0
#7 0x00007fce89717ca2 (/lib/x86_64-linux-gnu/libc.so.6+0x2fca2)
#8 0x0000000001290c8d (opt+0x1290c8d)
#9 0x0000000001286718 (opt+0x1286718)
#10 0x0000000001286dc0 (opt+0x1286dc0)
#11 0x000000000128704d (opt+0x128704d)
#12 0x00000000017dfe83 (opt+0x17dfe83)
#13 0x00000000017dff2c (opt+0x17dff2c)
#14 0x00000000017e0bda (opt+0x17e0bda)
#15 0x000000000078c9a1 (opt+0x78c9a1)
#16 0x00007fce89709f45 __libc_start_main
/build/eglibc-oGUzwX/eglibc-2.19/csu/libc-start.c:321:0
#17 0x00000000007e6f4b (opt+0x7e6f4b)
Stack dump:
0.      Program arguments: opt -loop-rotate -licm -loop-unroll -loop-vectorize
-o small-opt.bc small.bc 
1.      Running pass 'Function Pass Manager' on module 'small.bc'.
2.      Running pass 'Block Frequency Analysis' on function '@fn1'
Aborted (core dumped)



--------------------------------


int a, b;

void fn1 ()
{
  for (; a; a++)
    while (1) 
      {
        while (b) 
          ;
        if (a)
          break;
      }
}

int main ()
{
  fn1 ();
  return 0; 
}</pre>
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