[Bug tree-optimization/123120] phiprop does not always work

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123120

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2025-12-15
     Ever confirmed|0                           |1
           Assignee|unassigned at gcc dot gnu.org      |pinskia at gcc dot 
gnu.org

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
```
  # _16 = PHI <&D.35726(2), &a(3)>
  _2 = (long long int) d_7(D);
  D.35727 = _2;
  _9 = D.35727;
  _6 = *_16;
```


The current code just does:
```
      vuse = gimple_vuse (use_stmt);
      if (vphi)
        {
          if (vuse != gimple_phi_result (vphi))
            goto next;
        }
```

So we don't check that _16 can be changed by the store to D.35727 (which it
can't).

Let me see if I can fix this.