a) Write the following C function in Assembly. You must follow the System V 64-b

Question

a) Write the following C function in Assembly. You must follow the System V 64-bit calling convention and use AT&T; Syntax notation. Note: You cannot change the algorithm in any way so your assembly function must still be recursive. long fibonacci (long n) { if (n = = 0) return 0; else if (n = = 1) return 1;else return (fibonacci (n-1) + fibonacci (n-2)); } b) The Windows x86-64 calling convention passes function parameters in the registers RCX, RDX, R8 and R9 and returns values on register RAX. Caller saved registers are: RAX, RCX, RDX, R8, R9, R10 and R11, while callee-saved registers are RBX RBP, RDI, RSI, RSP, R12, R13, R14, and R15. Rewrite the assembly function from Part A using the Windows x86-64 calling convention instead of the System v 4- bit calling convention.

Explanation / Answer

1)

a)

Code:

include Irvine32.inc

.code
main PROC
mov ecx,0
push 10   
call fabonacci   
add esp, 4

main ENDP

fabonacci PROC C
add ecx,1
push ebp
mov ebp,esp
sub esp, 4   
mov eax,[ebp+8]

cmp eax,2
je interrupt
cmp eax,1
je interrupt

dec eax
push eax
call fabonacci
mov [ebp-4], eax

dec dword ptr [esp]
call fabonacci
add esp, 4

add eax, [ebp-4]

jmp Exit

interrupt:
mov eax, 1 ; start values 1,1
; dec eax ; start values 0,1

Exit:
mov esp, ebp
pop ebp   

ret   
fabonacci ENDP

END main

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