example 2-8.sa

《基于TI DSP的通用算法实现》程序代码

;Example 2 - 8. Single-Precision Floating-Point Division SA Listing for _divf

;================================================================
; Copyright 1998 by Texas Instruments Inc. All rights reserved.

; DIVSP.sa Syd Poland 05-01-98 for TMS320C67xx DSPs
; a4 = a4/b4
; ans = arg1/arg2 SP FP divide subroutine

;================================================================

	.text				; program memory
	.global _DIVSP,	__divf		; entry labels
	.align 32		 	; fetch packet boundary

__divf						; entry in rts6701 library
_DIVSP: .cproc arg1, arg2			; entry to SP FP divide subroutine

					; declare the input arguments
	.reg xn, two, tmp, ans, V	; just declare args, not need to allocate registers

	rcpsp	arg2, xn			; x1 = 1/arg2 [8-bits]
	extu	arg2, 1, 24, V	; exp2 = 0 ?
	zero	two					; LS halfword = 0
	mpysp	arg2, xn, tmp		; tmp = arg2*x1
	set	two, 30, 30, two	
					; two = 2.0 in SP FP (0x4000_0000)
	subsp	two, tmp, tmp		; tmp = 2.0-(arg2*x1)
	mpysp	xn, tmp, xn		; x2 = x1*(2-arg2*x1) [16-bits]
	mpysp	arg2, xn, tmp		; tmp = arg2*x2
	subsp	two, tmp, tmp		; tmp = 2.0-(arg2*x2)
	mpysp	xn, tmp, xn		; x3 = x2*(2-arg2*x2) [32-bits]
[V]	mpysp	arg1, xn, ans		
					; ans = arg1*(1/arg2) {xn = 1/arg2}
[!V]	set	arg1, 0, 30, ans	
					; return exp/mant = all ones (div by 0)
	.return	ans			; return value like c routines
	.endproc			; not use .end to show the end
;