x86汇编（MASM）中的Euler的Totient函数

.386 
.model flat, stdcall
.stack 4096

ExitProcess PROTO, dwExitCode:DWORD 

.code
;------------------------------------------------------------------------------
; _phi@4 (int x)
;
; Calculates Euler's totient function using the product formula.
;
; param:
  x     TEXTEQU <[ebp+8]>       ;integer argument
;
; Exit: The result is stored in eax
;------------------------------------------------------------------------------
_phi@4:
        push    ebp             ; setup stack, save regs
        mov     ebp, esp
        push    ebx
        push    ecx
        push    edx

        mov     ecx, x          ; init result as x

; Consider the prime factors of x and subtract their multiples
; from the result
        mov     ebx, 2          ; initialize loop counter p
L3:     mov     eax, ebx
        mul     ebx 
        cmp     DWORD PTR x, eax ; loop if( x >= p * p)
        jnge    endL3;

; Check if p is a prime factor
        cdq
        mov     eax, x
        div     ebx 
        cmp     edx, 0          ; if(x % p == 0)
        jne     noprime

;if yes, update x and result 
L2:     cdq 
        mov     eax, x
        div     ebx
        cmp     edx, 0          ; if(x % p == 0)
        jne     endL2
        mov     x  , eax        ; x /= p            
        jmp     L2
endL2:
        cdq
        mov     eax, ecx
        div     ebx
        sub     ecx, eax        ;result -= result / p
noprime:    
        inc     ebx 
        jmp     L3
endL3:      

; If x has a prime factor greater than sqrt(x)
        cmp     DWORD PTR x, 1
        jle     finish
        cdq
        mov     eax, ecx
        div     DWORD PTR x
        sub     ecx, eax
finish:
        mov     eax, ecx

        pop     edx
        pop     ecx
        pop     ebx
        pop     ebp
        ret     4

main:
        push    100
        call    _phi@4
        INVOKE  ExitProcess, 0

        END     main