[llvm-bugs] [Bug 43957] New: Wrong debug info generated at -O3 (-O0 is correct)

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=43957

            Bug ID: 43957
           Summary: Wrong debug info generated at -O3 (-O0 is correct)
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: LLVM Codegen
          Assignee: unassignedclangbugs at nondot.org
          Reporter: shuo.d at outlook.com
                CC: davide at freebsd.org, llvm-bugs at lists.llvm.org,
                    neeilans at live.com, richard-llvm at metafoo.co.uk

The expected output from lldb should be 36902. However, compiled with "-O3",
lldb outputs 36901.



$ 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
$ lldb-trunk -s cmds -b a.out
(lldb) target create "a.out"
Current executable set to '/home/sding/LLDB-testing/reduce/30986/report/a.out'
(x86_64).
(lldb) command source -s 0 'cmds'
Executing commands in '/home/sding/LLDB-testing/reduce/30986/report/cmds'.
(lldb) b 6
Breakpoint 1: where = a.out`main + 10 at abc.c:6:7, address =
0x000000000040048a
(lldb) r
Process 10166 stopped
* thread #1, name = 'a.out', stop reason = breakpoint 1.1
    frame #0: 0x000000000040048a a.out`main at abc.c:6:7
   3      --b;
   4      unsigned l_801 = 36901;
   5      ++l_801;
-> 6      if (a) // optimize_me_not0
   7        b = 0;
   8    }

Process 10166 launched: '/home/sding/LLDB-testing/reduce/30986/report/a.out'
(x86_64)
(lldb) p l_801
(unsigned int) $0 = 36901
(lldb) kill
Process 10166 exited with status = 9 (0x00000009) 
(lldb) q



$ clang-trunk -g abc.c -O0
$ lldb-trunk -s cmds -b a.out
(lldb) target create "a.out"
Current executable set to '/home/sding/LLDB-testing/reduce/30986/report/a.out'
(x86_64).
(lldb) command source -s 0 'cmds'
Executing commands in '/home/sding/LLDB-testing/reduce/30986/report/cmds'.
(lldb) b 6
Breakpoint 1: where = a.out`main + 43 at abc.c:6:7, address =
0x00000000004004ab
(lldb) r
Process 18492 stopped
* thread #1, name = 'a.out', stop reason = breakpoint 1.1
    frame #0: 0x00000000004004ab a.out`main at abc.c:6:7
   3      --b;
   4      unsigned l_801 = 36901;
   5      ++l_801;
-> 6      if (a) // optimize_me_not0
   7        b = 0;
   8    }

Process 18492 launched: '/home/sding/LLDB-testing/reduce/30986/report/a.out'
(x86_64)
(lldb) p l_801
(unsigned int) $0 = 36902
(lldb) kill
Process 18492 exited with status = 9 (0x00000009) 
(lldb) q



$ cat abc.c
char a, b;
int main() {
  --b;
  unsigned l_801 = 36901;
  ++l_801;
  if (a) // optimize_me_not0
    b = 0;
}



$ cat cmds
b 6
r
p l_801
kill
q

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