Re: [PATCH] middle-end/114931 - type_hash_canon and structual equality types

[Jakub Jelinek <jakub@redhat.com>]

On Fri, May 03, 2024 at 09:11:20PM +0200, Martin Uecker wrote:
> > TYPE_CANONICAL as used by the middle-end cannot express this but
> 
> Hm. so how does it work now for arrays?

Do you have a testcase which doesn't work correctly with the arrays?

E.g. same_type_for_tbaa has
  type1 = TYPE_MAIN_VARIANT (type1);
  type2 = TYPE_MAIN_VARIANT (type2);

  /* Handle the most common case first.  */
  if (type1 == type2)
    return 1;

  /* If we would have to do structural comparison bail out.  */
  if (TYPE_STRUCTURAL_EQUALITY_P (type1)
      || TYPE_STRUCTURAL_EQUALITY_P (type2))
    return -1;

  /* Compare the canonical types.  */
  if (TYPE_CANONICAL (type1) == TYPE_CANONICAL (type2))
    return 1;

  /* ??? Array types are not properly unified in all cases as we have
     spurious changes in the index types for example.  Removing this
     causes all sorts of problems with the Fortran frontend.  */
  if (TREE_CODE (type1) == ARRAY_TYPE
      && TREE_CODE (type2) == ARRAY_TYPE)
    return -1;
...
and later compares alias sets and the like.
So, even if int[] and int[0] have different TYPE_CANONICAL, they
will be considered maybe the same.  Also, guess get_alias_set
has some ARRAY_TYPE handling...

Anyway, I think we should just go with Richi's patch.

	Jakub