Texas Instruments TMS320C64X - Manual (Page 118)

DSP_bitrev_cplx
4-90
4.8 Obsolete Functions
4.8.1 FFT
Complex Bit-Reverse DSP_bitrev_cplx
NOTE: This function is provided for backward compatibility with the C62x
DSPLIB. It has not been optimized for the C64x architecture. You are advised
to use one of the newly added FFT functions which have been optimized for the
C64x.
Function void DSP_bitrev_cplx (int *x, short *index, int nx)
Arguments x[nx] Pointer to complex input vector x of size nx
index[ ] Array of size
∼
sqrt(nx) created by the routine digitrev_index
(provided in the directory ‘support\fft’).
nx Number of elements in vector x. nx must be a power of 2.
Description This function bit-reverses the position of elements in complex vector x. This
function is used in conjunction with FFT routines to provide the correct format
for the FFT input or output data. The bit-reversal of a bit-reversed order array
yields a linear-order array.
Algorithm TI retains all rights, title and interest in this code and only authorizes the use
of this code on TI TMS320 DSPs manufactured by TI. This is the C equivalent
of the assembly code without restrictions. Note that the assembly code is hand
optimized and restrictions may apply.
void DSP_bitrev_cplx (int *x, short *index, int nx)
{
int i;
short i0, i1, i2, i3;
short j0, j1, j2, j3;
int xi0, xi1, xi2, xi3;
int xj0, xj1, xj2, xj3;
short t;
int a, b, ia, ib, ibs;
int mask;