[Bug ipa/84658] [7/8 Regression] -O3 -fmerge-all-constants causes incorrect for-each loop generation.

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84658

--- Comment #13 from Richard Biener <rguenth at gcc dot gnu.org> ---
So you can loses the TREE_ADDRESSABLE restriction somewhat in requiring at most
one decl to be TREE_ADDRESSABLE - that's the one you need to keep, the others
may become aliases.  Given TREE_ADDRESSABLE isn't reliable for !TREE_STATIC
vars
we can't merge any exported decls that way.  Consider

const int foo1;
const int foo2;

int *bar();  // in other TU, returns address of foo1

int main ()
{
  if (bar() != &foo2)
    ...;
}

not sure if we want to do hand-waving saying that we can't possibly have
points-to sets mentioning those without seeing the function IL.  Well,
might be similarly hand-waving as the reference aliasing issue.

So we could drop the TREE_STATIC restriction if TREE_ADDRESSABLE is reliable
within the current TU.