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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 - opt cannot terminate with "opt -mem2reg -loop-unswitch -reg2mem -licm -structurizecfg -reg2mem -licm""
   href="https://bugs.llvm.org/show_bug.cgi?id=40949">40949</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>opt cannot terminate with "opt -mem2reg -loop-unswitch -reg2mem -licm -structurizecfg -reg2mem -licm"
          </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>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>cszide@163.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Created <span class=""><a href="attachment.cgi?id=21558" name="attach_21558" title=".bc file of the source code">attachment 21558</a> <a href="attachment.cgi?id=21558&action=edit" title=".bc file of the source code">[details]</a></span>
.bc file of the source code

For this test case, opt cannot terminate. I have tested it using godbolt, and
the opt 6/7/truck versions all have this problem. The outputs of opt 6/7/truck
are as follows.

opt truck:
/compiler-explorer/c-preload/compiler-wrapper: line 21:  8512 Killed           
      "$@"

Compiler returned: 137

opt 7:
compiler-explorer/c-preload/compiler-wrapper: line 21: 13372 Killed            
     "$@"

Compiler returned: 137

opt 6:
/compiler-explorer/c-preload/compiler-wrapper: line 21: 18355 Killed           
      "$@"

Compiler returned: 137

The followings are my test environment and test steps.

$clang -v
clang version 9.0.0 (trunk 355281)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/jack-zhou/Documents/llvm/llvm_truck/llvm/build4/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.3.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.3.0
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64

$clang -O3 -c -emit-llvm  -mllvm -disable-llvm-optzns small.c -o small.bc

$opt -mem2reg -loop-unswitch -reg2mem -licm -structurizecfg -reg2mem -licm 
small.bc -o small-opt.bc

The following is the source code of small.c

#include "csmith.h"
a() {
  int32_t b[8];
  uint32_t c;
  uint64_t d = 4073709551610;
  for (;;) {
    uint8_t e;
    for (; 8;)
      for (;; c++) {
        if (b)
          return 0;
        if (d)
          break;
      }
  }
}</pre>
        </div>
      </p>


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