[PATCH] Fix optimization regression in constant folder

[Eric Botcazou]

> I don't think this is correct.  [Note: all this TYPE_IS_SIZETYPE
> specialities have to go somewhen - they really confuse things]

Well, this is the documented behaviour of TYPE_IS_SIZETYPE:

/* In an INTEGER_TYPE, it means the type represents a size.  We use
   this both for validity checking and to permit optimizations that
   are unsafe for other types.  Note that the C `size_t' type should
   *not* have this flag set.  The `size_t' type is simply a typedef
   for an ordinary integer type that happens to be the type of an
   expression returned by `sizeof'; `size_t' has no special
   properties.  Expressions whose type have TYPE_IS_SIZETYPE set are
   always actual sizes.  */

and we really need this to simplify complex size calculations in Ada.

> First of all, this misses a (optimization) testcase.  Second, why do we use
> signed sizetype calculations when we want unsigned semantics as far as
> overflow behavior is concerned?

I don't think we want unsigned semantics, we want "size" semantics, i.e we 
don't care about overflow in size calculations.

-- 
Eric Botcazou