Task: Maximum Computation in Assembly with 64-bit C Call

Navigate to tasks/max-c-calls-x64/support and open main.c

In this subdirectory you should have implemented the maximum assembly language calculation on a 64-bit system. Start the program from exercises 4 and 5 in such a way that you run it using a 64-bit system.

TIP: https://en.wikipedia.org/wiki/X86_calling_conventions.

The first thing to note is that on the x64 architecture the registers are 8 bytes in size and have different names than the 32-bit ones (in addition to extending the traditional ones: eax register becomes rax, ebx register becomes rbx, etc., there are new ones: R10-R15: for more information see here).

Also, on x64 architecture parameters are no longer sent to the stack, but put in registers. The first 3 parameters are put in: rdi, rsi and rdx registers. This is not a uniformly adopted convention. This convention is only valid on Linux, on Windows there are other registers which are used to pass the parameters of a function. The calling convention requires that, for functions with a variable number of arguments, rax register be set to the number of vector registers used to pass arguments. printf() is a variable argument count function, and unless you use registers other than those mentioned in the previous paragraph for passing arguments, you must set rax = 0 before calling. Read more here.