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<head>
<base href="https://bugs.llvm.org/">
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Wrong debug info generated at -O3 (-O0 is correct)"
href="https://bugs.llvm.org/show_bug.cgi?id=43955">43955</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Wrong debug info generated at -O3 (-O0 is correct)
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</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>LLVM Codegen
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>shuo.d@outlook.com
</td>
</tr>
<tr>
<th>CC</th>
<td>davide@freebsd.org, llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
</td>
</tr></table>
<p>
<div>
<pre>The expected output from lldb should be 5. However, compiled with "-O3", lldb
outputs 0.
$ clang-trunk -v
clang version 10.0.0 (trunk 375507)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/9
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.4.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/9
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/9
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64
$ clang-trunk -g abc.c -O3
abc.c:6:13: warning: implicitly declaring library function 'printf' with type
'int (const char *, ...)' [-Wimplicit-function-declaration]
void f(g) { printf("%X\n", g); }
^
abc.c:6:13: note: include the header <stdio.h> or explicitly provide a
declaration for 'printf'
1 warning generated.
$ lldb-trunk -s cmds -b a.out
(lldb) target create "a.out"
Current executable set to '/home/sding/LLDB-testing/reduce/30972/report/a.out'
(x86_64).
(lldb) command source -s 0 'cmds'
Executing commands in '/home/sding/LLDB-testing/reduce/30972/report/cmds'.
(lldb) b 25
Breakpoint 1: where = a.out`main + 781 at abc.c:25:7, address =
0x000000000040083d
(lldb) r
Process 21519 stopped
* thread #1, name = 'a.out', stop reason = breakpoint 1.1
frame #0: 0x000000000040083d a.out`main at abc.c:25:7
22 for (; i < 5; i++)
23 h(e[i]);
24 h(1);
-> 25 f(b ^ 5); // optimize_me_not0
26 }
Process 21519 launched: '/home/sding/LLDB-testing/reduce/30972/report/a.out'
(x86_64)
(lldb) p i
(int) $0 = 0
$ clang-trunk -g abc.c -O0
abc.c:6:13: warning: implicitly declaring library function 'printf' with type
'int (const char *, ...)' [-Wimplicit-function-declaration]
void f(g) { printf("%X\n", g); }
^
abc.c:6:13: note: include the header <stdio.h> or explicitly provide a
declaration for 'printf'
1 warning generated.
$ lldb-trunk -s cmds -b a.out
(lldb) target create "a.out"
Current executable set to '/home/sding/LLDB-testing/reduce/30972/report/a.out'
(x86_64).
(lldb) command source -s 0 'cmds'
Executing commands in '/home/sding/LLDB-testing/reduce/30972/report/cmds'.
(lldb) b 25
Breakpoint 1: where = a.out`main + 164 at abc.c:25:5, address =
0x0000000000400634
(lldb) r
Process 29588 stopped
* thread #1, name = 'a.out', stop reason = breakpoint 1.1
frame #0: 0x0000000000400634 a.out`main at abc.c:25:5
22 for (; i < 5; i++)
23 h(e[i]);
24 h(1);
-> 25 f(b ^ 5); // optimize_me_not0
26 }
Process 29588 launched: '/home/sding/LLDB-testing/reduce/30972/report/a.out'
(x86_64)
(lldb) p i
(int) $0 = 5
$ cat abc.c
int a[56];
int b;
short c;
static int d;
static int e[] = {4, 0, 4, 0, 4};
void f(g) { printf("%X\n", g); }
void h(g) {
b = b & 4095 ^ a[(b ^ g) & 255];
b = b & 4095 ^ a[(b ^ 8) & 255];
b = b & 4095 ^ a[(b ^ 6) & 5];
}
int main() {
int i, j;
i = 0;
h(c);
for (; i < 3; i++) {
j = 0;
for (; j < 2; j++)
h(d);
}
i = 0;
for (; i < 5; i++)
h(e[i]);
h(1);
f(b ^ 5); // optimize_me_not0
}
$ cat cmds
b 25
r
p i
kill
q</pre>
</div>
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