<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 - Emitted binary code changes when -g is enabled at -O1"
   href="https://bugs.llvm.org/show_bug.cgi?id=50427">50427</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Emitted binary code changes when -g is enabled at -O1
          </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>normal
          </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>tlwang@uwaterloo.ca
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
          </td>
        </tr></table>
      <p>
        <div>
        <pre>The .text section for the following program (transformed_program0.c) changes
after toggling the -g flag.

$ cat transformed_program0.c
int a;
char b, c;
short d() {
  {
    int e;
  f:;
    int g = b != 7;
    if (!g)
      goto h;
    if (!a)
      goto i;
    return a;
  i:
    b = b + 1;
    goto f;
  h:;
  }
  return c;
}
int main() {}
$
$ /home/cnsun/usr/bin/clang-trunk -v
clang version 13.0.0 (<a href="https://github.com/llvm/llvm-project.git">https://github.com/llvm/llvm-project.git</a>
ac06f6d06de408c00923708dd8a795b6ba9d23d7)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/cnsun/usr/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/9
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64
$
$ /home/cnsun/usr/bin/clang-trunk -O1 -w transformed_program0.c ; objdump
--disassemble a.out > "no-g.txt"
$ /home/cnsun/usr/bin/clang-trunk -O1 -g -w transformed_program0.c ; objdump
--disassemble a.out > "g.txt"
$ diff g.txt no-g.txt
104c104
<   401120:     eb 28                   jmp    40114a <d+0x3a>
---
<span class="quote">>   401120:      eb 27                   jmp    401149 <d+0x39></span >
106c106
<   401128:     80 c2 f9                add    $0xf9,%dl
---
<span class="quote">>   401128:      80 c2 01                add    $0x1,%dl</span >
109,123c109,122
<   401132:     75 14                   jne    401148 <d+0x38>
<   401134:     8d 4a 08                lea    0x8(%rdx),%ecx
<   401137:     88 0d ef 2e 00 00       mov    %cl,0x2eef(%rip)        # 40402c
<b>
<   40113d:     fe c2                   inc    %dl
<   40113f:     0f 94 c1                sete   %cl
<   401142:     84 d2                   test   %dl,%dl
<   401144:     75 ea                   jne    401130 <d+0x20>
<   401146:     eb 02                   jmp    40114a <d+0x3a>
<   401148:     89 c1                   mov    %eax,%ecx
<   40114a:     0f be 05 e3 2e 00 00    movsbl 0x2ee3(%rip),%eax        #
404034 <c>
<   401151:     84 c9                   test   %cl,%cl
<   401153:     0f 44 c6                cmove  %esi,%eax
<   401156:     c3                      retq
<   401157:     66 0f 1f 84 00 00 00    nopw   0x0(%rax,%rax,1)
<   40115e:     00 00
---
<span class="quote">>   401132:      75 13                   jne    401147 <d+0x37>
>   401134:  88 15 f2 2e 00 00       mov    %dl,0x2ef2(%rip)        # 40402c <b>
>   40113a:  80 c2 01                add    $0x1,%dl
>   40113d:  80 fa 08                cmp    $0x8,%dl
>   401140:  0f 94 c1                sete   %cl
>   401143:  75 eb                   jne    401130 <d+0x20>
>   401145:  eb 02                   jmp    401149 <d+0x39>
>   401147:  89 c1                   mov    %eax,%ecx
>   401149:  0f be 05 e4 2e 00 00    movsbl 0x2ee4(%rip),%eax        # 404034 <c>
>   401150:  84 c9                   test   %cl,%cl
>   401152:  0f 44 c6                cmove  %esi,%eax
>   401155:  c3                      retq
>   401156:  66 2e 0f 1f 84 00 00    nopw   %cs:0x0(%rax,%rax,1)
>   40115d:  00 00 00</span ></pre>
        </div>
      </p>


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