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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Variable's value late availability after SimplifyCFG at Os"
href="https://bugs.llvm.org/show_bug.cgi?id=52240">52240</a>
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<th>Summary</th>
<td>Variable's value late availability after SimplifyCFG at Os
</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>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>DebugInfo
</td>
</tr>
<tr>
<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_47 value is not available at line 9 even if it has been assigned.
The value become available again at line 10.
>From bisect, this behavior may be caused by SimplifyCFGPass on function (main).
$ cat a.c
int a, c, d;
int *b[4];
int main()
{
int f; {
int *l_47 = &a;
int e = 0;
for (; e < 4; e++)
b[e] = &a;
f = c;
}
d = f; }
$ 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 -Os -o opt a.c
$ lldb opt
(lldb) target create "opt"
Current executable set to '/home/stepping/64/reduce/opt' (x86_64).
(lldb) b 6
Breakpoint 1: where = opt`main at a.c:9:12, address = 0x0000000000400478
(lldb) run
Process 282 launched: '/home/stepping/64/reduce/opt' (x86_64)
Process 282 stopped
* thread #1, name = 'opt', stop reason = breakpoint 1.1
frame #0: 0x0000000000400478 opt`main at a.c:9:12
6 int *l_47 = &a;
7 int e = 0;
8 for (; e < 4; e++)
-> 9 b[e] = &a;
10 f = c;
11 }
12 d = f; }
(lldb) frame var
(int) f = <variable not available>
(int) e = 0
(int *) l_47 = <variable not available>
(lldb) n
Process 282 stopped
* thread #1, name = 'opt', stop reason = step over
frame #0: 0x0000000000400497 opt`main at a.c:10:10
7 int e = 0;
8 for (; e < 4; e++)
9 b[e] = &a;
-> 10 f = c;
11 }
12 d = f; }
(lldb) frame var
(int) f = <variable not available>
(int) e = 0
(int *) l_47 = 0x0000000000601040</pre>
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