<html>
    <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 - Infinite loop at -Os"
   href="https://bugs.llvm.org/show_bug.cgi?id=49556">49556</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Infinite loop at -Os
          </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>haoxintu@gmail.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Hi, all.

This small and valid code, small.c, makes Clang trunk hung on at compile time
at -Os. It seems that there exists an infinite loop. Note that this issue
exists in all clang-10.0.1 upwards and clang-6.0.1 downwards versions.

$cat small.c
#include <stdint.h>
int a, b;
int16_t c;
void d() {
  uint16_t *e = 0;
  int32_t f = 0;
  uint16_t **g = &e;
  for (; b; b++) {
    int64_t *i = a;
    for (; i; i++)
      *g = &f;
  }
  {
    int16_t *g = &c;
    int16_t **j = &g;
    for (; *e;)
      ;
    *g && (**j = 0);
    for (;; *e %= c)
      ;
  }
}

$clang -v
clang version 13.0.0 (<a href="https://github.com/llvm/llvm-project">https://github.com/llvm/llvm-project</a>
590ac0a26af4c9f63d5564be8c13b12d409a7fd9)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir:
/home/haoxin/haoxin-data/dut-research/compilers/llvm-project/build-20210310/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Candidate multilib: .;@m64
Selected multilib: .;@m64



Reproduced in godbolt: <a href="https://godbolt.org/z/nfsona">https://godbolt.org/z/nfsona</a>

Thanks,
Haoxin</pre>
        </div>
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