Texas Instruments TMS320C67 DSP Series Programmer's Reference Manual page 54

xh21 = x_h2p1 + x_l2p1;
xl20 = x_h2
xl21 = x_h2p1 - x_l2p1;
ptr_x0 = x;
ptr_x0[0] = xh0 + xh20;
ptr_x0[1] = xh1 + xh21;
ptr_x2 = ptr_x0;
x += 2;
j += 6;
predj = (j - fft_jmp);
if (!predj) x += fft_jmp;
if (!predj) j = 0;
xt0 = xh0 - xh20;
yt0 = xh1 - xh21;
xt1 = xl0 - xl21;
yt2 = xl1 - xl20;
xt2 = xl0 + xl21;
yt1 = xl1 + xl20;
ptr_x2[l1 ] = xt1 * co1 - yt1 * si1;
ptr_x2[l1+1] = yt1 * co1 + xt1 * si1;
ptr_x2[h2 ] = xt0 * co2 - yt0 * si2;
ptr_x2[h2+1] = yt0 * co2 + xt0 * si2;
ptr_x2[l2 ] = xt2 * co3 - yt2 * si3;
ptr_x2[l2+1] = yt2 * co3 + xt2 * si3;
}
tw_offset += fft_jmp;
stride = stride>>2;
}/* end while */
j = offset>>2;
ptr_x0 = ptr_x;
y0 = ptr_y;
/*l0 = _norm(n_max) - 17;
l0=0;
for(k=30;k>=0;k--)
if( (n_max & (1 << k)) == 0 )
l0++;
DSPF_sp_ifftSPxSP
- x_l2;
get size of fft */
DSPLIB Reference 4-29