vec_cx_mpy_13.c

dsp6713开发板的许多例程.对入门特别有用

void vec_cx_mpy(const short *restrict a, const short *restrict b,
                short *restrict c, int len, int shift)
{
    int i;
    unsigned a3_a2, a1_a0;             /* Packed 16-bit values        */
    unsigned b3_b2, b1_b0;             /* Packed 16-bit values        */
    int      c3,c2, c1,c0;             /* Separate 32-bit results     */
    unsigned c3_c2, c1_c0;             /* Packed 16-bit values        */

    for (i = 0; i < len; i += 4)
    {
        /* Load two complex numbers from the a[] array.               */
        /* The complex values loaded are represented as 'a3 + a2 * j' */
        /* and 'a1 + a0 * j'.  That is, the real components are a3    */
        /* and a1, and the imaginary components are a2 and a0.        */
        a3_a2 = _hi(*(const double *) &a[i]);
        a1_a0 = _lo(*(const double *) &a[i]);

        /* Load two complex numbers from the b[] array.               */
        b3_b2 = _hi(*(const double *) &b[i]);
        b1_b0 = _lo(*(const double *) &b[i]);

        /* Perform the complex multiplies using _dotp2/_dotpn2.      */
        c3 = _dotpn2(b3_b2, a3_a2);                  /* Real         */
        c2 = _dotp2 (b3_b2, _packlh2(a3_a2, a3_a2)); /* Imaginary    */

        c1 = _dotpn2(b1_b0, a1_a0);                  /* Real         */
        c0 = _dotp2 (b1_b0, _packlh2(a1_a0, a1_a0)); /* Imaginary    */

        /* Pack the 16-bit results from the upper halves of the      */
        /* 32-bit results into 32-bit words.                         */
        c3_c2 = _packh2(c3, c2);
        c1_c0 = _packh2(c1, c0);

        /* Store the results. */
        *(double *) &c[i] = _itod(c3_c2, c1_c0);
    }
}