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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Missing line information after SROA pass at Og"
href="https://bugs.llvm.org/show_bug.cgi?id=50286">50286</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Missing line information after SROA pass 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>The last assignment to a variable passed to an external function is not reached
in debugging.
If we set a breakpoint on line 11, with a next operation we will end up on line
15, thus skipping line 14 where the last assignment is done.
>From opt-bisect, the pass after which the line is not reached anymore is: SROA
pass.
Beside this, upon calling the external function, the variable v_0 appears to be
not available in lldb but we should see that its value is the same as v_1 from
its last assignment.
>From both asm and IR, we can see that after SROA pass the first two parameters
to test_out are the same variable/register:
ASM ----------
400533: 89 df mov %ebx,%edi
400535: 89 de mov %ebx,%esi
400537: 89 ea mov %ebp,%edx
400539: e8 a2 ff ff ff callq 4004e0 <test_out>
IR -------------
call void @test_out(i32 %6, i32 %6, i32 %3, i32 %10) #3, !dbg !26
Could it be possible to map this parameter passing to the last assignment line?
$ cat a.c
int test_in();
void test_out(int v_0, int v_1, int v_2, int v_3);
int main()
{
int v_0, v_1, v_2, v_3;
v_0 = test_in();
v_1 = test_in();
v_2 = test_in();
v_3 = test_in();
v_1 = (v_2 * ~(~v_0 + v_3));
v_0 = (v_2 >> (v_3 < (v_0 < v_1)));
v_0 = (v_2 * v_3);
v_0 = v_1;
v_3 = ((v_1 & (v_2 & v_3)) < v_0);
test_out(v_0, v_1, v_2, v_3);
return 0;
}
$ cat lib/test.c
#include <stdio.h>
int ctr = 0;
int test_in() {
return ctr++;
}
void test_out(int v_0, int v_1, int v_2, int v_3) {
printf("%d%d%d%d", v_0, v_1, v_2, v_3);
}
$ 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 -Og -o opt lib/test.c a.c
$ lldb opt
(lldb) target create "opt"
Current executable set to '/home/stepping/test/opt' (x86_64).
(lldb) b 11
Breakpoint 1: where = opt`main + 35 at a.c:11:15, address = 0x0000000000400523
(lldb) r
Process 36 launched: '/home/stepping/test/opt' (x86_64)
Process 36 stopped
* thread #1, name = 'opt', stop reason = breakpoint 1.1
frame #0: 0x0000000000400523 opt`main at a.c:11:15
8 v_1 = test_in();
9 v_2 = test_in();
10 v_3 = test_in();
-> 11 v_1 = (v_2 * ~(~v_0 + v_3));
12 v_0 = (v_2 >> (v_3 < (v_0 < v_1)));
13 v_0 = (v_2 * v_3);
14 v_0 = v_1;
(lldb) n
Process 36 stopped
* thread #1, name = 'opt', stop reason = step over
frame #0: 0x0000000000400528 opt`main at a.c:15:21
12 v_0 = (v_2 >> (v_3 < (v_0 < v_1)));
13 v_0 = (v_2 * v_3);
14 v_0 = v_1;
-> 15 v_3 = ((v_1 & (v_2 & v_3)) < v_0);
16 test_out(v_0, v_1, v_2, v_3);
17
18 return 0;
(lldb) frame var v_0
(int) v_0 = <variable not available>
(lldb) frame var v_1
(int) v_1 = -6</pre>
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