Texas Instruments TMS320C64X - Manual (Page 127)

DSP_fft
4-99 C64x+ DSPLIB Reference
#include <stdio.h>
#include <stdlib.h>
#if 0
# define DIG_REV(i, m, j) ((j) = (_shfl(_rotl(_bitr(_deal(i)), 16)) >> (m)))
#else
# define DIG_REV(i, m, j) \
do { \
unsigned _ = (i); \
_ = ((_ & 0x33333333) << 2) | ((_ & ~0x33333333) >> 2); \
_ = ((_ & 0x0F0F0F0F) << 4) | ((_ & ~0x0F0F0F0F) >> 4); \
_ = ((_ & 0x00FF00FF) << 8) | ((_ & ~0x00FF00FF) >> 8); \
_ = ((_ & 0x0000FFFF) << 16) | ((_ & ~0x0000FFFF) >> 16); \
(j) = _ >> (m); \
} while (0)
#endif
void fft_cn
(
const short *restrict w,
int n,
short *restrict x,
short *restrict y
)
{
int stride, i, j, k, t, s, m;
short xh0, xh1, xh20, xh21;
short xl0, xl1, xl20, xl21;
short xt0, yt0, xt1, yt1;
short xt2, yt2, xt3, yt3;
/*−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−*/
/* Inform the compiler that the input array ”x”, twiddle factor array */
/* ”w” and output array ”y” are double word aligned. In addition, the */
/* number of points to be transformed is assumed to be greater than or */
/* equal to 16, and less than 32768. */
/*−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−*/
#ifndef NOASSUME