computing hash values, integral types versus struct/class

Question

hello

I would like to know if there is a difference in speed between computing hash value (for example std::map key) of primitive integral type, such as int64_t and pod type, for example struct { int16_t v[4]; };. what about int128_t versus struct {int32_t v[4];}?

I know this is going to implementation specific, so my question ultimately pertains to gnu standard library. Thanks

the link I found very useful http://stackoverflow.com/questions/1829639/how-can-i-use-a-custom-type-for-keys-in-a-boostunordered-map