[Bug debug/90946] New: gcc generates wrong debug information at -O3

[qrzhang at gatech dot edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90946

            Bug ID: 90946
           Summary: gcc generates wrong debug information at -O3
           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 affects the trunk at "-O3". The expected output is "105487". However, at
-O3, it prints "40369".

Bisect points to r270902. 



$ gcc-trunk -v
gcc version 10.0.0 20190619 (experimental) [trunk revision 272472] (GCC)
$ gdb -v
GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.5) 7.11.1

#Correct output#
$ gcc-trunk  -g abc.c outer.c
$ gdb -x cmds -batch a.out
Breakpoint 1 at 0x40052d: file abc.c, line 30.

Breakpoint 1, g (j=1) at abc.c:30
30          optimize_me_not();
$1 = 105487


#Wrong output#
$ gcc-trunk  -g abc.c outer.c -O3
$ gdb -x cmds -batch a.out
Breakpoint 1 at 0x400396: file abc.c, line 30.

Breakpoint 1, g (j=1) at abc.c:30
30          optimize_me_not();
$1 = 40369




$ cat abc.c
static short a = 8;
int b, f, h;
int *c;
volatile int d;
int e(j) {}
static char g(j) {
  unsigned short k;
  int l_756 = 40369, i = 0;
  int *l = &l_756;
  for (; i < 4; i++)
    f = 4071609;
  if (f) {
    int m[1];
    if (j)
      ;
    else {
      int **n = &c;
      *n = e(&l_756);
      **n = h;
      **n |= 0;
    }
  } else {
    k = b;
    *c = k;
    h &= 8;
  }
  d;
  if (a) {
    *l = 105487;
    optimize_me_not();
    return 8;
  }
  int o = &l;
}
int main() { g(1); }

$ cat outer.c
void optimize_me_not() {}

$ cat cmds
b 30
r
p l_756
kill
q