On 6/19/19 1:53 PM, Jan Hubicka wrote:
- ctype = CLASSTYPE_AS_BASE (ctype);
+ {
+ if (!tree_int_cst_equal (TYPE_SIZE (ctype),
+ TYPE_SIZE (CLASSTYPE_AS_BASE (ctype))))
+ ctype = CLASSTYPE_AS_BASE (ctype);
+ }
tree clobber = build_clobber (ctype);
I have noticed we build a distinct as-base type in rather more cases than
strictly necessary. For instance when there's a member of reference type or
we have a non-trivial dtor. (CLASSTYPE_NON_LAYOUT_POD_P gets set by a bunch
of things that don't affect ABI layout)
Avoiding the extra copies at first place would be great. In my
understanding the types differ by virtual bases and also by their size
since the fake types are not padded to multiply of their alignment.
I guess this can be tested ahead of producing the copy and saving some
memory...
I am not sure if my C++ FE abilities are on par to implement this tough.
I don't think it's simple to fix there, just unfortunate. your
understanding is correct, and I think your workaround will work.
However, remember it's possible for T == CLASSTYPE_AS_BASE (T), so might
be worth checking that before doing the size comparison?
It'd be great to comment on why you're not just using classtype_as_base
there. I suppose I'm serializing this stuff too, with the same
inefficiencies ...
nathan
--
Nathan Sidwell
