s7_if.sa

dsp6713开发板的许多例程.对入门特别有用

***********************************************************************
*         Copyright (C) 1996-2001 Texas Instruments Incorporated
*                      All Rights Reserved
*         IF7 ASSEMBLY OPTIMIZER SOURCE - Example 6-49
*         From Programmer's Guide
***********************************************************************
********* ASSEMBLY OPTIMIZER CODE: *******************

        .def _if_then_sa

_if_then_sa: .cproc   a, cword, mask, theta

        .reg    cond, if, ai, sum, cntr
 
        MVK     32,cntr			; cntr = 32
	ZERO	sum			; sum = 0

LOOP:   .trip 32
	AND	.S2X	cword,mask,cond	; cond = codeword & mask
 [cond]	MVK	.S2	1,cond		; !(!(cond))
	CMPEQ	.L2	theta,cond,if	; (theta == !(!(cond)))
	LDH	.D1	*a++,ai		; a[i]
   [if]	ADD	.L1	sum,ai,sum	; sum += a[i]
  [!if]	SUB	.D1	sum,ai,sum	; sum -= a[i]
	SHL	.S1	mask,1,mask	; mask = mask << 1;
 [cntr] ADD	.L2	-1,cntr,cntr	; decrement counter
 [cntr] B	.S1	LOOP		; for LOOP

	.return	sum

        .endproc