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<base href="https://bugs.llvm.org/">
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<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 at -O0 when compiling through -S"
href="https://bugs.llvm.org/show_bug.cgi?id=52027">52027</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Emitted binary code changes at -O0 when compiling through -S
</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>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Common Code Generator Code
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>tlwang@uwaterloo.ca
</td>
</tr>
<tr>
<th>CC</th>
<td>cnsun@uwaterloo.ca, llvm-bugs@lists.llvm.org
</td>
</tr>
<tr>
<th>Blocks</th>
<td>37728
</td>
</tr></table>
<p>
<div>
<pre>The .text section of program0.c changes when the program is compiled through
-S.
$ cat program0.c
int main(int a, char *b[]) { a && 0; }
$
$ clang-trunk -v
clang version 14.0.0 (<a href="https://github.com/llvm/llvm-project.git">https://github.com/llvm/llvm-project.git</a>
2303391d1f543f4e57f9ed0fc68bad2d4cf890dc)
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
$
$ clang-trunk -O0 -S program0.c -o program0.s
$ clang-trunk -O0 -c program0.s -o program0.out
$ objdump --disassemble --section=.text program0.out > s.txt
$ clang-trunk -O0 -c program0.c -o program0.out
$ objdump --disassemble --section=.text program0.out > no_s.txt
$ diff s.txt no_s.txt
16,23c16,23
< 1b: 74 07 je 24 <main+0x24>
< 1d: 31 c0 xor %eax,%eax
< 1f: 88 45 ef mov %al,-0x11(%rbp)
< 22: eb 00 jmp 24 <main+0x24>
< 24: 8a 45 ef mov -0x11(%rbp),%al
< 27: 8b 45 fc mov -0x4(%rbp),%eax
< 2a: 5d pop %rbp
< 2b: c3 retq
---
<span class="quote">> 1b: 0f 84 0a 00 00 00 je 2b <main+0x2b>
> 21: 31 c0 xor %eax,%eax
> 23: 88 45 ef mov %al,-0x11(%rbp)
> 26: e9 00 00 00 00 jmpq 2b <main+0x2b>
> 2b: 8a 45 ef mov -0x11(%rbp),%al
> 2e: 8b 45 fc mov -0x4(%rbp),%eax
> 31: 5d pop %rbp
> 32: c3 retq</span ></pre>
</div>
</p>
<div id="referenced">
<hr style="border: 1px dashed #969696">
<b>Referenced Bugs:</b>
<ul>
<li>
[<a class="bz_bug_link
bz_status_NEW "
title="NEW - [meta] Make llvm passes debug info invariant"
href="https://bugs.llvm.org/show_bug.cgi?id=37728">Bug 37728</a>] [meta] Make llvm passes debug info invariant
</li>
</ul>
</div>
<br>
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