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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 - Variable's value not available from second loop iteration at Og after SpeculateAroundPHIs"
href="https://bugs.llvm.org/show_bug.cgi?id=52241">52241</a>
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<th>Summary</th>
<td>Variable's value not available from second loop iteration at Og after SpeculateAroundPHIs
</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>
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<th>OS</th>
<td>Linux
</td>
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<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>DebugInfo
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>cristianassaiante@outlook.com
</td>
</tr>
<tr>
<th>CC</th>
<td>jdevlieghere@apple.com, keith.walker@arm.com, llvm-bugs@lists.llvm.org, paul_robinson@playstation.sony.com
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</tr></table>
<p>
<div>
<pre>Variable l_2 value is not available at line 4 after second loop iteration but
it is available at line 5.
>From bisect, this behavior may be caused by SpeculateAroundPHIsPass on function
(main).
$ cat a.c
int main() {
int l_2 = 4;
for (; b <= 3; b++)
a = l_2 &= 0 == 0;
}
$ clang -v
clang version 13.0.0
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/bin
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/7.5.0
Candidate multilib: .;@m64
Selected multilib: .;@m64
$ lldb -v
lldb version 13.0.0
$ clang -g -Og -o opt a.c
$ lldb opt
(lldb) target create "opt"
Current executable set to '/home/stepping/75/reduce/opt' (x86_64).
(lldb) b main
Breakpoint 1: where = opt`main at a.c:4:10, address = 0x0000000000400480
(lldb) run
Process 321 launched: '/home/stepping/75/reduce/opt' (x86_64)
Process 321 stopped
* thread #1, name = 'opt', stop reason = breakpoint 1.1
frame #0: 0x0000000000400480 opt`main at a.c:4:10
1 int a, b;
2 int main() {
3 int l_2 = 4;
-> 4 for (; b <= 3; b++)
5 a = l_2 &= 0 == 0;
6 }
(lldb) frame var
(int) l_2 = 4
(lldb) n
Process 321 stopped
* thread #1, name = 'opt', stop reason = step over
frame #0: 0x00000000004004a0 opt`main at a.c:5:13
2 int main() {
3 int l_2 = 4;
4 for (; b <= 3; b++)
-> 5 a = l_2 &= 0 == 0;
6 }
(lldb) frame var
(int) l_2 = 0
(lldb) n
Process 321 stopped
* thread #1, name = 'opt', stop reason = step over
frame #0: 0x00000000004004a3 opt`main at a.c:4:3
1 int a, b;
2 int main() {
3 int l_2 = 4;
-> 4 for (; b <= 3; b++)
5 a = l_2 &= 0 == 0;
6 }
(lldb) frame var
(int) l_2 = <variable not available>
(lldb) n
Process 321 stopped
* thread #1, name = 'opt', stop reason = step over
frame #0: 0x00000000004004a0 opt`main at a.c:5:13
2 int main() {
3 int l_2 = 4;
4 for (; b <= 3; b++)
-> 5 a = l_2 &= 0 == 0;
6 }
(lldb) frame var
(int) l_2 = 0</pre>
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