Aligned types and passing arguments by value

Question

Passing aligned types or structures with aligned types by value doesn\'t work with some implementations. This breaks STL containers, because some of the methods (such as resize)

Answer 1

I think the only safe way to do this in general is to pass by reference. Some platforms (e.g. Xbox 360) support passing vector arguments in registers, but I don't think this is possible on x86.

For the std::vector case, you'll need to make sure that the memory allocated is aligned to 16 bytes; otherwise you'll get crashes when you try to perform most operations on unaligned vectors.

If you're supporting multiple platforms, a safe plan is to use a typedef e.g.

typedef const MyVector& MyVectorParameter;

You can then change the typedef on platforms that support vector pass-by-value.

Answer 2

the oftenly used resize() function is causing all the alignment and perhaps you can try to specialise vector template for __m128 ?