[Bug tree-optimization/114207] modref gets confused by vecotorized code ` -O3 -fno-tree-forwprop`

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114207

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=111613
           Keywords|                            |wrong-code
             Status|UNCONFIRMED                 |NEW
          Component|c                           |tree-optimization
            Summary|Wrong code bug since GCC    |modref gets confused by
                   |12.1                        |vecotorized code ` -O3
                   |                            |-fno-tree-forwprop`
   Target Milestone|---                         |12.4
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2024-03-02

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.

The IR is:
```
  vectp.7_7 = &s_4(D)->b;
  vectp.7_8 = vectp.7_7 + 18446744073709551612;
  vect__1.8_9 = MEM <vector(2) int> [(int *)vectp.7_8];
  vect__2.9_10 = VEC_PERM_EXPR <vect__1.8_9, vect__1.8_9, { 1, 0 }>;
  MEM <vector(2) int> [(int *)s_4(D)] = vect__2.9_10;

```

modref thinks this only reads s->b somehow.