Texas Instruments TMS320C67 DSP Series Programmer's Reference Manual page 47

DSPF_sp_fftSPxSP
4-22
x2 = ptr_x0[2];
x4 = ptr_x0[4];
x6 = ptr_x0[6];
ptr_x0 += 8;
xh0_0 = x0 + x4;
xh1_0 = x1 + x5;
xh0_1 = x2 + x6;
xh1_1 = x3 + x7;
if (radix == 2) {
xh0_0 = x0;
xh1_0 = x1;
xh0_1 = x2;
xh1_1 = x3;
}
yt0 = xh0_0 + xh0_1;
yt1 = xh1_0 + xh1_1;
yt4 = xh0_0 - xh0_1;
yt5 = xh1_0 - xh1_1;
xl0_0 = x0 - x4;
xl1_0 = x1 - x5;
xl0_1 = x2 - x6;
xl1_1 = x3 - x7;
if (radix == 2) {
xl0_0 = x4;
xl1_0 = x5;
xl1_1 = x6;
xl0_1 = x7;
}
yt2 = xl0_0 + xl1_1;
yt3 = xl1_0 - xl0_1;
yt6 = xl0_0 - xl1_1;
yt7 = xl1_0 + xl0_1;
if (radix == 2) {
yt7 = xl1_0 - xl0_1;
yt3 = xl1_0 + xl0_1;
}
x3 = ptr_x0[3];
x5 = ptr_x0[5];
x7 = ptr_x0[7];