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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 - Missing variables after loop strength reduction at Og"
href="https://bugs.llvm.org/show_bug.cgi?id=51734">51734</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Missing variables after loop strength reduction 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>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>Upon calling a function from an external module, the variable l_75 passed to it
is not visible from lldb. Using -opt-bisect-limit we discovered that the pass
causing the symbols disappear is "Loop Strength Reduction on loop".
$ cat a.c
void a()
{
char b = 0, l_78 = 1;
int l_49 = 2;
short l_55 = 3, l_75 = 3;
for (; b <= 8; ++b)
{
test_nop();
test_support_2996(l_49, l_55, l_75, l_78);
l_75 = 0;
}
}
int main ()
{
a();
}
$ cat lib/test.c
#include <stdio.h>
#include <stdint.h>
#include "test.h"
void test_nop() {
printf("\n");
}
void test_support_2996(int l_49, int l_55, int l_75, int l_78) {
printf("%d %d %d %d", l_49, l_55, l_75, l_78);
}
$ cat lib/test.h
#pragma once
void test_nop();
void test_support_2996(int l_49, int l_55, int l_75, int l_78);
$ 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 revision c2c977ce50597b0e5186afc342c5784bd0aa6973
lldb revision c2c977ce50597b0e5186afc342c5784bd0aa6973
$ clang -g -O3 -o opt lib/test.c a.c
$ lldb opt
(lldb) target create "opt"
Current executable set to '/home/cristianrichie/71/reduce/opt' (x86_64).
(lldb) b 8
Breakpoint 1: 2 locations.
(lldb) r
Process 4253 launched: '/home/cristianrichie/71/reduce/opt' (x86_64)
Process 4253 stopped
* thread #1, name = 'opt', stop reason = breakpoint 1.2
frame #0: 0x0000000000401190 opt`main [inlined] a at a.c:8:1
5 short l_55 = 3, l_75 = 3;
6 for (; b <= 8; ++b)
7 {
-> 8 test_nop();
9 test_support_2996(l_49, l_55, l_75, l_78);
10 l_75 = 0;
11 }
(lldb) frame var
(short) l_55 = 3
(int) l_49 = 2
(char) l_78 = '\x01'
(lldb) frame var l_75
error: no variable named 'l_75' found in this frame</pre>
</div>
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