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<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Clang-trunk Generates Wrong Debug values with -O1"
href="https://bugs.llvm.org/show_bug.cgi?id=41925">41925</a>
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<th>Summary</th>
<td>Clang-trunk Generates Wrong Debug values with -O1
</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>
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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>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>DebugInfo
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>yuanboli233@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>aprantl@apple.com, davide@freebsd.org, jdevlieghere@apple.com, keith.walker@arm.com, llvm-bugs@lists.llvm.org, paul_robinson@playstation.sony.com, vsk@apple.com
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<p>
<div>
<pre>$ 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
char a, b;
int main() {
char l_177 = 2;
for (; b <= 0; b++)
for (; a >= 0; a--) {
++l_177;
optimize_me_not();
}
}
$ cat outer.c
optimize_me_not() {}
$ cat cmds
b 7
r
p l_177
kill
q
$ 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 + 66 at abc.c:7:7, address =
0x00000000004004c2
(lldb) r
Process 10423 stopped
* thread #1, name = 'a.out', stop reason = breakpoint 1.1
frame #0: 0x00000000004004c2 a.out`main at abc.c:7:7
4 for (; b <= 0; b++)
5 for (; a >= 0; a--) {
6 ++l_177;
-> 7 optimize_me_not();
8 }
9 }
Process 10423 launched: '/home/ybli/Projects/LLDB-testing/reduce.llvm/a.out'
(x86_64)
(lldb) p l_177
(char) $0 = '\x03'
(lldb) kill
Process 10423 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 + 32 at abc.c:7:7, address =
0x00000000004004a0
(lldb) r
Process 31526 stopped
* thread #1, name = 'a.out', stop reason = breakpoint 1.1
frame #0: 0x00000000004004a0 a.out`main at abc.c:7:7
4 for (; b <= 0; b++)
5 for (; a >= 0; a--) {
6 ++l_177;
-> 7 optimize_me_not();
8 }
9 }
Process 31526 launched: '/home/ybli/Projects/LLDB-testing/reduce.llvm/a.out'
(x86_64)
(lldb) p l_177
(char) $0 = '\x02'
(lldb) kill
Process 31526 exited with status = 9 (0x00000009)
(lldb) q
The bisection result is
correct: (the case shows l_177 could not materialize)
BISECT: running pass (46) Simplify the CFG on function
BISECT: NOT running pass (47) Combine redundant instructions on function
not working:
BISECT: running pass (46) Simplify the CFG on function
BISECT: running pass (47) Combine redundant instructions on function</pre>
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