[Bug debug/90131] New: wrong debug info at -O3

[qrzhang at gatech dot edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90131

            Bug ID: 90131
           Summary: wrong debug info 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: ---

This issue is similar to bug 90074 --- same flag, same gcc versions. The
bisection also points to r255267. It appears that the issue remains after the
patch. 


$ gcc-trunk -v
gcc version 9.0.1 20190417 (experimental) [trunk revision 270407] (GCC)

$ gdb -v
GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.5) 7.11.1


#Wrong result#
$ gcc-trunk -g abc.c outer.c -O3
$ gdb -x cmds -batch a.out
Breakpoint 1 at 0x40040f: file abc.c, line 16.

Breakpoint 1, main () at abc.c:16
16            optimize_me_not();
$1 = 9


#Correct result#
$ gcc-trunk -g abc.c outer.c
$ gdb -x cmds -batch a.out
Breakpoint 1 at 0x4004c8: file abc.c, line 16.

Breakpoint 1, main () at abc.c:16
16            optimize_me_not();
$1 = 0



$ cat abc.c
volatile long a;
int b[9][1];
static short c[2][1] = {3};
int main() {
  int i, d, e;
  i = 0;
  for (; i < 9; i++)
    a = b[i][0];
  i = 0;
  for (; i < 2; i++) {
    d = 0;
    for (; d < 1; d++) {
      e = 0;
      for (; e < 1; e++)
        a = c[i][e];
      optimize_me_not();
    }
  }
}

$ cat outer.c
void optimize_me_not() {}

$ cat cmds
b 16
r
p i
kill
q