factclasmfunc.sa

来自「DSP常用C语言算法」· SA 代码 · 共 15 行

;Factclasmfunc.sa Linear ASM function called from C to find factorial
      
      	    .ref	_factclasmfunc ;Linear ASM func called from C
_factclasmfunc: .cproc	number	   ;start of linear ASM function
		    .reg	a,b            ;asm optimizer directive
		    mv	number,b       ;set-up loop count in b
		    mv  	number,a       ;move number to a
		    sub     b,1,b          ;decrement loop counter

loop:		    mpy	a,b,a     	   ;n(n-1)
		    sub	b,1,b          ;decrement loop counter  
   [b] 	    b		loop       	   ;loop back to loop if count # 0
		    .return	a              ;result to calling function
		    .endproc               ;end of linear asm function