How to load a single precise data in linear assembly code?

Hi May,

First, the LDW instruction doesn't distinguish between fixed and floating data which you want to load, what it see is just a 32-bit content located in the target memory. The result should be ok if you check the register val0, or you can paste the array prototype here for us to have a try.

Second, it seems you miss the step to clear sum1:sum0 to zero before the loop in your linear assembly code, so the ADDDP instruction will produce wrong result if there is unexpected sum1:sum0 as input.

Allen

Hi Allen,

       I got the conclusion, because I tried the following code:

           .def        _dotp

_dotp:   .cproc     a, b ,cnt

              .reg         val0,val1

             .reg         prod1:prod0, sum1:sum0

;loop:   

             LDW         *a++, val0

;            LDW          *b++, val1

  ;          MPYSP2DP     val0, val1, prod1:prod0

    ;        ADDDP        prod1:prod0, sum1:sum0, sum1:sum0

;[cnt]     SUB            cnt,1,cnt

;[cnt]     B                  loop

        ;     .return     sum1:sum0

            .return   val0

             .endproc

void main()

{

                     double c = 0.0;

                      float a[10] = {0.1};

                     float    b[10] = {0.2}; 

                      c = dotp(a,b,1);

                     printf("%lf\n",c);

}

the result of c is wrong!

  Can you tell me why?

   Thanks, Allen

Hi May,

In your program, c is defined as double type, but the dotp function just load a 32-bit data and pass it to val0, so the MSB of c will be zero.

Just modify the c as float type then you can get right result.

Allen