[Bug debug/94005] New: gcc generates wrong debug information at -Og

[qrzhang at gatech dot edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94005

            Bug ID: 94005
           Summary: gcc generates wrong debug information at -Og
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
          Assignee: unassigned at gcc dot gnu.org
          Reporter: qrzhang at gatech dot edu
  Target Milestone: ---

It appears to be a regression in gcc-9.

bisection points to g:36f6476b80ca559ff0fc436d2ab84130b


The value of l at line 11 is 153. At -Og it generates l=0. O3 and O2 works
fine.


$ gcc-trunk -v
gcc version 10.0.1 20200302 (experimental) [master revision
778a77357ca:87d8bb8fb8c:917e56a94f9d3189d7fa9d1944b7513258195887] (GCC)

#correct value:

$ gcc-trunk -g  abc.c
$ gdb -x cmds -batch a.out
Breakpoint 1 at 0x4004ec: file abc.c, line 11.

Breakpoint 1, i () at abc.c:11
11        l = e; //   optimize_me_not()
$1 = 153
Kill the program being debugged? (y or n) [answered Y; input not from terminal]
[Inferior 1 (process 24999) killed]


#incorrect value:

$ gcc-trunk -g -Og abc.c
$ gdb -x cmds -batch a.out
Breakpoint 1 at 0x400495: file abc.c, line 11.

Breakpoint 1, i () at abc.c:11
11        l = e; //   optimize_me_not()
$1 = 0
Kill the program being debugged? (y or n) [answered Y; input not from terminal]
[Inferior 1 (process 32681) killed]

$ cat abc.c
int a, b = -7L;
short d;
static int e;
char f;
char g() {}
int h(c) {}
void i() {
  int l;
  (a && g()) > (e && h(d = 5));
  f = l = b & 159;
  l = e; //   b here
}
int main() { i(); }


$ cat cmds
b abc.c:11
r
p l
kill
q