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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 - Variable's value late availability after VectorCombinePass at Os"
href="https://bugs.llvm.org/show_bug.cgi?id=51942">51942</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Variable's value late availability after VectorCombinePass 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>
<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>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
</td>
</tr></table>
<p>
<div>
<pre>A variable (l_113) value is visile after its declarations and it becomes
available only at line 11.
>From opt-bisect, it seems that the pass after which this behaviour occurs is:
VectorCombinePass on function (main)
$ cat a.c
int a, b, g ;
int *c = &a;
char d, e, f ;
void h(i) {
int l_113 = 9;
d = *c |=
f =
e
<= 5 ;
int *l_80 = b;
g = *c || *l_80 ^ i;
}
int main()
{
h(5);
}
$ 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/debuginfo-analysis/issues/issue15/opt' (x86_64).
(lldb) b h
Breakpoint 1: where = opt`h at a.c:9:35, address = 0x0000000000400478
(lldb) r
Process 40 launched: '/home/stepping/debuginfo-analysis/issues/issue15/opt'
(x86_64)
Process 40 stopped
* thread #1, name = 'opt', stop reason = breakpoint 1.1
frame #0: 0x0000000000400478 opt`h(i=5) at a.c:9:35
6 d = *c |=
7 f =
8 e
-> 9 <= 5 ;
10 int *l_80 = b;
11 g = *c || *l_80 ^ i;
12
(lldb) frame var
(int) i = 5
(int) l_113 = <variable not available>
(int *) l_80 = <variable not available>
(lldb) s
Process 40 stopped
* thread #1, name = 'opt', stop reason = step in
frame #0: 0x0000000000400481 opt`h(i=5) at a.c:7:24
4 void h(i) {
5 int l_113 = 9;
6 d = *c |=
-> 7 f =
8 e
9 <= 5 ;
10 int *l_80 = b;
(lldb) frame var
(int) i = 5
(int) l_113 = <variable not available>
(int *) l_80 = <variable not available>
(lldb) s
Process 40 stopped
* thread #1, name = 'opt', stop reason = step in
frame #0: 0x0000000000400488 opt`h(i=5) at a.c:9:35
6 d = *c |=
7 f =
8 e
-> 9 <= 5 ;
10 int *l_80 = b;
11 g = *c || *l_80 ^ i;
12
(lldb) frame var
(int) i = 5
(int) l_113 = <variable not available>
(int *) l_80 = <variable not available>
(lldb) n
Process 40 stopped
* thread #1, name = 'opt', stop reason = step over
frame #0: 0x000000000040048b opt`h(i=5) at a.c:6:8
3 char d, e, f ;
4 void h(i) {
5 int l_113 = 9;
-> 6 d = *c |=
7 f =
8 e
9 <= 5 ;
(lldb) n
Process 40 stopped
* thread #1, name = 'opt', stop reason = step over
frame #0: 0x00000000004004a1 opt`h(i=5) at a.c:11:12
8 e
9 <= 5 ;
10 int *l_80 = b;
-> 11 g = *c || *l_80 ^ i;
12
13 }
14 int main()
(lldb) frame var
(int) i = 5
(int) l_113 = 9
(int *) l_80 = <variable not available></pre>
</div>
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