The motivation to have the new vectorcall calling convention is to make use of as many registers as possible to pass function arguments rather than pushing the function arguments to stack and reading them from stack inside the function. Targeting this calling convention on performance critical functions can increase the performance since now most of the interaction is happening with registers (as demonstrated below with a code sample). For more information on vectorcall calling convention, please refer to the following URLs:
- http://msdn.microsoft.com/en-us/library/dn375768.aspx
- http://blogs.msdn.com/b/vcblog/archive/2013/07/12/introducing-vector-calling-convention.aspx
Intel® C++ Compiler 14.0 Update 1 doesn’t support _vectorcall calling convention. Instead users can use __regcall calling convention which is a workaround for _vectorcall (demonstrated in this article).