s4_dotp.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
*         DOTP4 ASSEMBLY OPTIMIZER SOURCE - Example 6-24
*         From Programmer's Guide
***********************************************************************
********* ASSEMBLY OPTIMIZER CODE: *******************

        .def _dotp_sa

_dotp_sa: .cproc   a, b

        .reg    sum, sum0, sum1, cntr 
        .reg	ai_i1, bi_i1, pi, pi1
  
        MVK     50,cntr         ; cntr = 100/2
        ZERO    sum0            ; multiply result = 0
        ZERO    sum1            ; multiply result = 0
 
LOOP:   .trip 50
        LDW	    *a++,ai_i1      ; load ai & a1 from memory
        LDW	    *b++,bi_i1      ; load bi & b1 from memory
        MPY	    ai_i1,bi_i1,pi  ; ai * bi
        MPYH    ai_i1,bi_i1,pi1 ; ai+1 * bi+1
        ADD	    pi,sum0,sum0    ; sum0 += (ai * bi)
        ADD	    pi1,sum1,sum1   ; sum1 += (ai+1 * bi+1)
 [cntr] SUB	    cntr,1,cntr     ; decrement loop counter
 [cntr] B	    LOOP            ; branch to loop

        ADD     sum0,sum1,sum   ; compute final result

        .return sum

        .endproc