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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 - Missing Variables information at Og"
href="https://bugs.llvm.org/show_bug.cgi?id=47093">47093</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Missing Variables information at Og
</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>Linux
</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>DebugInfo
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>massarelli@diag.uniroma1.it
</td>
</tr>
<tr>
<th>CC</th>
<td>jdevlieghere@apple.com, keith.walker@arm.com, llvm-bugs@lists.llvm.org, paul_robinson@playstation.sony.com
</td>
</tr></table>
<p>
<div>
<pre>At line 9 lldb says that variables l_1876 and l_2441 are optimized out, but
they are actually used.
$ cat -n a.c
1 short a;
2 int b, d = 4;
3 int *c = &b;
4 void func_3() {
5 int **l_1876 = &c;
6 int e = 1;
7 if (d) {
8 int *l_2441 = a;
9 (**l_1876) = l_2441;
10 }
11 *l_1876 = &e;
12 }
13 int main() { func_3(); }
$ cat a.c
short a;
int b, d = 4;
int *c = &b;
void func_3() {
int **l_1876 = &c;
int e = 1;
if (d) {
int *l_2441 = a;
(**l_1876) = l_2441;
}
*l_1876 = &e;
}
int main() { func_3(); }
$ clang -v
clang version 12.0.0 (<a href="https://github.com/llvm/llvm-project.git">https://github.com/llvm/llvm-project.git</a>
bc8be3054067ac822fc6d9f4f8e64c841f530f16)
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 12.0.0
clang revision bc8be3054067ac822fc6d9f4f8e64c841f530f16
llvm revision bc8be3054067ac822fc6d9f4f8e64c841f530f16
$ clang -g -Og -o opt a.c
$ lldb opt
(lldb) target create "opt"
Current executable set to 'opt' (x86_64).
(lldb) b func_3
Breakpoint 1: where = opt`func_3 at a.c:6:7, address = 0x0000000000400480
(lldb) r
Process 66 launched: '/home/stepping/output/opt' (x86_64)
Process 66 stopped
* thread #1, name = 'opt', stop reason = breakpoint 1.1
frame #0: 0x0000000000400480 opt`func_3 at a.c:6:7
3 int *c = &b;
4 void func_3() {
5 int **l_1876 = &c;
-> 6 int e = 1;
7 if (d) {
8 int *l_2441 = a;
9 (**l_1876) = l_2441;
(lldb) s
Process 66 stopped
* thread #1, name = 'opt', stop reason = step in
frame #0: 0x0000000000400488 opt`func_3 at a.c:7:7
4 void func_3() {
5 int **l_1876 = &c;
6 int e = 1;
-> 7 if (d) {
8 int *l_2441 = a;
9 (**l_1876) = l_2441;
10 }
(lldb) s
Process 66 stopped
* thread #1, name = 'opt', stop reason = step in
frame #0: 0x0000000000400491 opt`func_3 at a.c:8:19
5 int **l_1876 = &c;
6 int e = 1;
7 if (d) {
-> 8 int *l_2441 = a;
9 (**l_1876) = l_2441;
10 }
11 *l_1876 = &e;
(lldb) s
Process 66 stopped
* thread #1, name = 'opt', stop reason = step in
frame #0: 0x0000000000400498 opt`func_3 at a.c:9:7
6 int e = 1;
7 if (d) {
8 int *l_2441 = a;
-> 9 (**l_1876) = l_2441;
10 }
11 *l_1876 = &e;
12 }
(lldb) p l_2441
error: Couldn't materialize: couldn't get the value of variable l_2441: no
location, value may have been optimized out
error: errored out in DoExecute, couldn't PrepareToExecuteJITExpression
(lldb) p l_1876
error: Couldn't materialize: couldn't get the value of variable l_1876: no
location, value may have been optimized out
error: errored out in DoExecute, couldn't PrepareToExecuteJITExpression
(lldb) di
opt`func_3:
0x400480 <+0>: movl $0x1, -0x4(%rsp)
0x400488 <+8>: cmpl $0x0, 0x200b99(%rip) ; __dso_handle + 7
0x40048f <+15>: je 0x4004a1 ; <+33> at a.c
0x400491 <+17>: movswl 0x200ba8(%rip), %eax ; a
-> 0x400498 <+24>: movq 0x200b91(%rip), %rcx ; c
0x40049f <+31>: movl %eax, (%rcx)
0x4004a1 <+33>: leaq -0x4(%rsp), %rax
0x4004a6 <+38>: movq %rax, 0x200b83(%rip) ; c
0x4004ad <+45>: retq
(lldb)</pre>
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