PATCH RFA: PR 29286: Handle placement new aliasing issues

[Eric Botcazou]

> tree_ssa_useless_type_conversion_1 does not strip them but fold does :).

fold preserves types.

> Not really, TYPE_REF_CAN_ALIAS_ALL causes the new pointer type to
> alias every type based aliasing while the new tree code only causes
> that variable to be aliasing every type.

I don't see the problem, other variables have the non-TYPE_REF_CAN_ALIAS_ALL 
variant of the pointer type, that variable has the TYPE_REF_CAN_ALIAS_ALL 
variant.  It's equivalent to non-TYPE_READONLY vs TYPE_READONLY variant of a 
type.

-- 
Eric Botcazou