+ /* From the former common C and C++ langhook implementation:
+
+ Unfortunately, there is no canonical form of a pointer type.
+ In particular, if we have `typedef int I', then `int *', and
+ `I *' are different types. So, we have to pick a canonical
+ representative. We do this below.
+
+ Technically, this approach is actually more conservative that
+ it needs to be. In particular, `const int *' and `int *'
+ should be in different alias sets, according to the C and C++
+ standard, since their types are not the same, and so,
+ technically, an `int **' and `const int **' cannot point at
+ the same thing.
+
+ But, the standard is wrong. In particular, this code is
+ legal C++:
+
+ int *ip;
+ int **ipp = &ip;
+ const int* const* cipp = ipp;
+ And, it doesn't make sense for that to be legal unless you
+ can dereference IPP and CIPP. So, we ignore cv-qualifiers on
+ the pointed-to types. This issue has been reported to the
+ C++ committee.
+
+ In addition to the above canonicalization issue, with LTO
+ we should also canonicalize `T (*)[]' to `T *' avoiding
+ alias issues with pointer-to element types and pointer-to
+ array types.
+
+ Likewise we need to deal with the situation of incomplete
+ pointed-to types and make `*(struct X **)&a' and
+ `*(struct X {} **)&a' alias. Otherwise we will have to
+ guarantee that all pointer-to incomplete type variants
+ will be replaced by pointer-to complete type variants if
+ they are available.
+
+ With LTO the convenient situation of using `void *' to
+ access and store any pointer type will also become
+ more apparent (and `void *' is just another pointer-to
+ incomplete type). Assigning alias-set zero to `void *'
+ and all pointer-to incomplete types is a not appealing
+ solution. Assigning an effective alias-set zero only
+ affecting pointers might be - by recording proper subset
+ relationships of all pointer alias-sets.
+
+ Pointer-to function types are another grey area which
+ needs caution. Globbing them all into one alias-set
+ or the above effective zero set would work.
+
+ For now just assign the same alias-set to all pointers.
+ That's simple and avoids all the above problems. */
+ else if (POINTER_TYPE_P (t)
+ && t != ptr_type_node)
+ return get_alias_set (ptr_type_node);
+