[llvm-bugs] [Bug 50475] New: Missing line information after EarlyCSE and InstCombine pass at Og

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=50475

            Bug ID: 50475
           Summary: Missing line information after EarlyCSE and
                    InstCombine pass at Og
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: DebugInfo
          Assignee: unassignedbugs at nondot.org
          Reporter: cristianassaiante at outlook.com
                CC: jdevlieghere at apple.com, keith.walker at arm.com,
                    llvm-bugs at lists.llvm.org,
                    paul_robinson at playstation.sony.com

The last assignment to a variable passed to an external function is not reached
in debugging. If we put a breakpoint on line 14, after a next command we end up
in line 17 thus skipping lines 15 and 16 where the last assignment to v_0 and
v_1 is done. From opt-bisect, the pass after which line 15 is not reached
anymore is EarlyCSEPass and the pass after which line 16 is not reached anymore
is InstCombinePass.

$ cat a.c
int  test_in();
void test_out(int v_0, int v_1, int v_2, int v_3);

int main (void)
{
        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_1 > (v_2 - (v_3 <= v_0)));
        v_0 = (v_1 < (~v_2 <= (v_3 >= v_0)));

        v_3 = ((v_2 + v_3) >= v_0);
        v_0 = (v_2 | (!(v_3 * v_0) < v_1));
        v_1 = (v_3 % !(~!v_0 >= (v_2 + v_1)));
        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 14
Breakpoint 1: where = opt`main + 83 at a.c:14:14, address = 0x0000000000400553
(lldb) r
Process 155 launched: '/home/stepping/test/opt' (x86_64)
Process 155 stopped
* thread #1, name = 'opt', stop reason = breakpoint 1.1
    frame #0: 0x0000000000400553 opt`main at a.c:14:14
   11           v_1 = (!v_1 > (v_2 - (v_3 <= v_0)));
   12           v_0 = (v_1 < (~v_2 <= (v_3 >= v_0)));
   13   
-> 14           v_3 = ((v_2 + v_3) >= v_0);
   15           v_0 = (v_2 | (!(v_3 * v_0) < v_1));
   16           v_1 = (v_3 % !(~!v_0 >= (v_2 + v_1)));
   17           test_out(v_0, v_1, v_2, v_3);
(lldb) next
Process 155 stopped
* thread #1, name = 'opt', stop reason = step over
    frame #0: 0x000000000040055c opt`main at a.c:17:2
   14           v_3 = ((v_2 + v_3) >= v_0);
   15           v_0 = (v_2 | (!(v_3 * v_0) < v_1));
   16           v_1 = (v_3 % !(~!v_0 >= (v_2 + v_1)));
-> 17           test_out(v_0, v_1, v_2, v_3);
   18           return 0;
   19   }

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