Consider passing and returning Vector<T> in registers #5040
Description
Currently, even under the Unix amd64 ABI, Vector is always passed on the stack. However, since it is not (and can't easily become) an interop type, it would be reasonable to pass and return these structs in registers (since they are, by definition, the size of the SIMD registers supported on the target, if present). This would require work in both the vm and jit. Note that for the unix ABI, the classification of the type is done after the call to CheckIfSIMDAndUpdateSize(), so it would already be appropriately marked at that time.
category:cq
theme:calling-convention
skill-level:expert
cost:medium
impact:large