Microsoft x64 calling convention
The rulebook for function calls on 64-bit Windows - only four register arguments, rcx, rdx, r8 and r9, plus 32 bytes of reserved stack.
The Microsoft x64 convention passes the first four arguments in rcx, rdx, r8, r9 (by position), the rest on the stack above 32 bytes of shadow space, returns in rax, treats rbx, rbp, rdi, rsi, rsp and r12-r15 as callee-saved, and has no red zone.
Examples
Integer arguments go in
rcx,rdx,r8andr9, then on the stack, and the caller reserves 32 bytes of shadow space.
See also