fft.c

FFT算法应用与C6000系列

           co11 = w[j+3];    si11 = w[j+2];                               */
           co20 = w[j+5];    si20 = w[j+4];   // W^2 //                   */
           co21 = w[j+7];    si21 = w[j+6];                               */
           co30 = w[j+9];    si30 = w[j+8];   // W^3 //                   */
           co31 = w[j+11];   si31 = w[j+10];                              */
                                                                          */
           x_0 = x[0];       x_1 = x[1];         // perform 2 parallel // */
           x_2 = x[2];       x_3 = x[3];         // radix4 butterflies // */
                                                                          */
           x_l1_0 = x[l1  ]; x_l1_1 = x[l1+1];                            */
           x_l1_2 = x[l1+2]; x_l1_3 = x[l1+3];                            */
                                                                          */
           x_l2_0 = x[l2  ]; x_l2_1 = x[l2+1];                            */
           x_l2_2 = x[l2+2]; x_l2_3 = x[l2+3];                            */
                                                                          */
           x_h2_0 = x[h2  ]; x_h2_1 = x[h2+1];                            */
           x_h2_2 = x[h2+2]; x_h2_3 = x[h2+3];                            */
                                                                          */
           xh0_0  = x_0    + x_l1_0; xh1_0  = x_1    + x_l1_1;            */
           xh0_1  = x_2    + x_l1_2; xh1_1  = x_3    + x_l1_3;            */
                                                                          */
           xl0_0  = x_0    - x_l1_0; xl1_0  = x_1    - x_l1_1;            */
           xl0_1  = x_2    - x_l1_2; xl1_1  = x_3    - x_l1_3;            */
                                                                          */
           xh20_0 = x_h2_0 + x_l2_0; xh21_0 = x_h2_1 + x_l2_1;            */
           xh20_1 = x_h2_2 + x_l2_2; xh21_1 = x_h2_3 + x_l2_3;            */
                                                                          */
           xl20_0 = x_h2_0 - x_l2_0; xl21_0 = x_h2_1 - x_l2_1;            */
           xl20_1 = x_h2_2 - x_l2_2; xl21_1 = x_h2_3 - x_l2_3;            */
                                                                          */
           x0 = x;                                                        */
           x2 = x0;                 // copy pointers for output//         */
                                                                          */
           j += 12;                                                       */
           x += 4;                                                        */
           predj = (j - fft_jmp);   // check if reached end of //         */
           if (!predj) x += fft_jmp;// current twiddle factor section //  */
           if (!predj) j = 0;                                             */
                                                                          */
           x0[0] = xh0_0 + xh20_0; x0[1] = xh1_0 + xh21_0;                */
           x0[2] = xh0_1 + xh20_1; x0[3] = xh1_1 + xh21_1;                */
                                                                          */
           xt0_0 = xh0_0 - xh20_0;  yt0_0 = xh1_0 - xh21_0;               */
           xt0_1 = xh0_1 - xh20_1;  yt0_1 = xh1_1 - xh21_1;               */
                                                                          */
           xt1_0 = xl0_0 + xl21_0;  yt2_0 = xl1_0 + xl20_0;               */
           xt2_0 = xl0_0 - xl21_0;  yt1_0 = xl1_0 - xl20_0;               */
           xt1_1 = xl0_1 + xl21_1;  yt2_1 = xl1_1 + xl20_1;               */
           xt2_1 = xl0_1 - xl21_1;  yt1_1 = xl1_1 - xl20_1;               */
                                                                          */
           x2[h2  ] = (si10 * yt1_0 + co10 * xt1_0) >> 15;                */
           x2[h2+1] = (co10 * yt1_0 - si10 * xt1_0) >> 15;                */
                                                                          */
           x2[h2+2] = (si11 * yt1_1 + co11 * xt1_1) >> 15;                */
           x2[h2+3] = (co11 * yt1_1 - si11 * xt1_1) >> 15;                */
                                                                          */
           x2[l1  ] = (si20 * yt0_0 + co20 * xt0_0) >> 15;                */
           x2[l1+1] = (co20 * yt0_0 - si20 * xt0_0) >> 15;                */
                                                                          */
           x2[l1+2] = (si21 * yt0_1 + co21 * xt0_1) >> 15;                */
           x2[l1+3] = (co21 * yt0_1 - si21 * xt0_1) >> 15;                */
                                                                          */
           x2[l2  ] = (si30 * yt2_0 + co30 * xt2_0) >> 15;                */
           x2[l2+1] = (co30 * yt2_0 - si30 * xt2_0) >> 15;                */
                                                                          */
           x2[l2+2] = (si31 * yt2_1 + co31 * xt2_1) >> 15;                */
           x2[l2+3] = (co31 * yt2_1 - si31 * xt2_1) >> 15;                */
       }                                                                  */
   }-* end while *-                                                       */
                                                                          */
   y0 = ptr_y;                                                            */
   y1 = y0 + (int)(n>>1);                                                 */
   y2 = y1 + (int)(n>>1);                                                 */
   y3 = y2 + (int)(n>>1);                                                 */
   x0 = ptr_x;                                                            */
   x2 = ptr_x + (int)(n>>1);                                              */
   l1 = _norm(n) + 2;                                                     */
   j = 0;                                                                 */
   for (i = 0; i < n; i += 8)                                             */
   {                                                                      */
       h2 = _deal(j);                                                     */
       h2 = _bitr(h2);                                                    */
       h2 = _rotl(h2, 16);                                                */
       h2 = _shfl(h2);                                                    */
       h2 >>= l1;                                                         */
                                                                          */
       x_0 = x0[0]; x_1 = x0[1];                                          */
       x_2 = x0[2]; x_3 = x0[3];                                          */
       x_4 = x0[4]; x_5 = x0[5];                                          */
       x_6 = x0[6]; x_7 = x0[7];                                          */
       x0 += 8;                                                           */
                                                                          */
       xh0_0  = x_0 + x_4; xh1_0  = x_1 + x_5;                            */
       xl0_0  = x_0 - x_4; xl1_0  = x_1 - x_5;                            */
       xh20_0 = x_2 + x_6; xh21_0 = x_3 + x_7;                            */
       xl20_0 = x_2 - x_6; xl21_0 = x_3 - x_7;                            */
                                                                          */
       xt0_0 = xh0_0 - xh20_0;                                            */
       yt0_0 = xh1_0 - xh21_0;                                            */
       xt1_0 = xl0_0 + xl21_0;                                            */
       yt2_0 = xl1_0 + xl20_0;                                            */
       xt2_0 = xl0_0 - xl21_0;                                            */
       yt1_0 = xl1_0 - xl20_0;                                            */
                                                                          */
       y0[2*h2  ] = xh0_0 + xh20_0;                                       */
       y0[2*h2+1] = xh1_0 + xh21_0;                                       */
       y1[2*h2  ] = xt1_0;                                                */
       y1[2*h2+1] = yt1_0;                                                */
       y2[2*h2  ] = xt0_0;                                                */
       y2[2*h2+1] = yt0_0;                                                */
       y3[2*h2  ] = xt2_0;                                                */
       y3[2*h2+1] = yt2_0;                                                */
                                                                          */
       x_10 = x2[0]; x_11 = x2[1];                                        */
       x_12 = x2[2]; x_13 = x2[3];                                        */
       x_14 = x2[4]; x_15 = x2[5];                                        */
       x_16 = x2[6]; x_17 = x2[7];                                        */
       x2 += 8;                                                           */
                                                                          */
       xh0_1  = x_10 + x_14; xh1_1  = x_11 + x_15;                        */
       xl0_1  = x_10 - x_14; xl1_1  = x_11 - x_15;                        */
       xh20_1 = x_12 + x_16; xh21_1 = x_13 + x_17;                        */
       xl20_1 = x_12 - x_16; xl21_1 = x_13 - x_17;                        */
                                                                          */
       xt0_1 = xh0_1 - xh20_1;                                            */
       yt0_1 = xh1_1 - xh21_1;                                            */
       xt1_1 = xl0_1 + xl21_1;                                            */
       yt2_1 = xl1_1 + xl20_1;                                            */
       xt2_1 = xl0_1 - xl21_1;                                            */
       yt1_1 = xl1_1 - xl20_1;                                            */
                                                                          */
       y0[2*h2+2] = xh0_1 + xh20_1;                                       */
       y0[2*h2+3] = xh1_1 + xh21_1;                                       */
       y1[2*h2+2] = xt1_1;                                                */
       y1[2*h2+3] = yt1_1;                                                */
       y2[2*h2+2] = xt0_1;                                                */
       y2[2*h2+3] = yt0_1;                                                */
       y3[2*h2+2] = xt2_1;                                                */
       y3[2*h2+3] = yt2_1;                                                */
                                                                          */
       j += 4;                                                            */
       if (j == n>>2)                                                     */
       {                                                                  */
         j  += n>>2;                                                      */
         x0 += (int) n>>1;                                                */
         x2 += (int) n>>1;                                                */
       }                                                                  */
     }                                                                    */
 }                                                                        
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