[Bug tree-optimization/117601] Another missing optimization after rewrite of SCCP for overflow

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117601

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2024-11-15
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
This hunk to match.pd fixes this:
```
(simplify
 (convert (plus@2 (convert ADDR_EXPR@0) INTEGER_CST@1))
 (if (POINTER_TYPE_P (type)
      && tree_nop_conversion_p (TREE_TYPE(@2), TREE_TYPE (@0))
      && tree_nop_conversion_p (TREE_TYPE(@0), type))
  (pointer_plus @0 @1)))
```
And combined with the "hack" in PR 117572, we can almost optimize the original
testcase there.

The only issue is we don't recongize the above until it is too late for DSE to
happen and we end up with still in .optimized:
```
  h_391 = &o + 2;
  n = 3;
  o ={v} {CLOBBER(eos)};
  q[1] = 1;
  c = &p;
  *h_391 = 0;
  o ={v} {CLOBBER(eos)};
```

Though this is enough to workaround the issue reported in PR 117426.