I'm currently learning x64 assembly by myself and have trouble understanding what happen with the stack when calling an assembly procedure from c++. From what I currently understand from MSDN and ...

I'd listening some people saying __fastcall is faster than __cdecl and __stdcall cause it puts two parameters in register, instead of the one of other calls; but, in other hand, this is not the sta...

I have seen the fastcall notation appended before many functions. Why it is used?

Is the fastcall calling convention really faster than other calling conventions, such as cdecl? Are there any benchmarks out there that show how performance is affected by calling convention?

Could some one provide an example use of fastcall for use with gcc? If possible could you provide the equivalent call without using fastcall and explain how they would be different?