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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Clang-trunk generate wrong debug info under -O1"
href="https://bugs.llvm.org/show_bug.cgi?id=41548">41548</a>
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<th>Summary</th>
<td>Clang-trunk generate wrong debug info under -O1
</td>
</tr>
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<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Keywords</th>
<td>wrong-debug
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>DebugInfo
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>yuanboli233@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>davide@freebsd.org, jdevlieghere@apple.com, keith.walker@arm.com, llvm-bugs@lists.llvm.org, paul_robinson@playstation.sony.com
</td>
</tr></table>
<p>
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<pre>This problem also happens under O2 and O3.
$ clang-trunk --version
clang version 9.0.0 (trunk 355785)
Target: x86_64-unknown-linux-gnu
Thread model: posix
$ lldb-trunk --version
lldb version 9.0.0 (<a href="https://llvm.org/svn/llvm-project/lldb/trunk">https://llvm.org/svn/llvm-project/lldb/trunk</a> revision
355785)
clang revision 355785
llvm revision 355785
$ cat abc.c
short a;
int main() {
int l_2849 = 38358926;
if (a)
;
else
optimize_me_not();
l_2849 = 0;
}
$ cat outer.c
optimize_me_not() {}
$ clang-trunk -O0 -g abc.c outer.c
$ lldb-trunk -s cmds -b a.out
(lldb) target create "a.out"
Current executable set to 'a.out' (x86_64).
(lldb) command source -s 0 'cmds'
Executing commands in '/home/ybli/Projects/LLDB-testing/reduce.llvm/cmds'.
(lldb) b 7
Breakpoint 1: where = a.out`main + 42 at abc.c:7:5, address =
0x00000000004004aa
(lldb) r
Process 30735 stopped
* thread #1, name = 'a.out', stop reason = breakpoint 1.1
frame #0: 0x00000000004004aa a.out`main at abc.c:7:5
4 if (a)
5 ;
6 else
-> 7 optimize_me_not();
8 l_2849 = 0;
9 }
Process 30735 launched: '/home/ybli/Projects/LLDB-testing/reduce.llvm/a.out'
(x86_64)
(lldb) p l_2849
(int) $0 = 38358926
(lldb) kill
Process 30735 exited with status = 9 (0x00000009)
(lldb) q
$ clang-trunk -O1 -g abc.c outer.c
$ lldb-trunk -s cmds -b a.out
(lldb) target create "a.out"
Current executable set to 'a.out' (x86_64).
(lldb) command source -s 0 'cmds'
Executing commands in '/home/ybli/Projects/LLDB-testing/reduce.llvm/cmds'.
(lldb) b 7
Breakpoint 1: where = a.out`main + 14 at abc.c:7:5, address =
0x000000000040048e
(lldb) r
Process 6641 stopped
* thread #1, name = 'a.out', stop reason = breakpoint 1.1
frame #0: 0x000000000040048e a.out`main at abc.c:7:5
4 if (a)
5 ;
6 else
-> 7 optimize_me_not();
8 l_2849 = 0;
9 }
Process 6641 launched: '/home/ybli/Projects/LLDB-testing/reduce.llvm/a.out'
(x86_64)
(lldb) p l_2849
(int) $0 = 0
(lldb) kill
Process 6641 exited with status = 9 (0x00000009)
(lldb) q
Pass bisection suggests that the problem is related to LEA fixup:
Correct case:
BISECT: running pass (92) X86 Atom pad short functions on function
(optimize_me_not)
BISECT: NOT running pass (93) X86 LEA Fixup on function (optimize_me_not)
Incorrect case:
BISECT: running pass (92) X86 Atom pad short functions on function
(optimize_me_not)
BISECT: running pass (93) X86 LEA Fixup on function (optimize_me_not)</pre>
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