Texas Instruments TMS320C67 DSP Series Programmer's Reference Manual page 59

DSPF_sp_icfftr2_dif
Algorithm
4-34
This is the C equivalent of the assembly code without restrictions. Note that
the assembly code is hand optimized and restrictions may apply.
void DSPF_sp_icfftr2_dif(float* x, float* w, short n)
{
short n2, ie, ia, i, j, k, m;
float rtemp, itemp, c, s;
n2 = 1;
ie = n;
for(k=n; k > 1; k >>= 1)
{
ie >>= 1;
ia = 0;
for(j=0; j < ie; j++)
{
c = w[2*j];
s = w[2*j+1];
for(i=0; i < n2; i++)
{
m = ia + n2;
rtemp
x[2*ia]
itemp
x[2*ia+1] = x[2*ia+1] + x[2*m+1];
x[2*m]
x[2*m+1]
ia++;
}
ia += n2;
}
n2 <<= 1;
}
}
The follwoing C code is used to generate the coefficient table (non-bit re-
versed):
#include <math.h>
= x[2*ia] - x[2*m];
= x[2*ia] + x[2*m];
= x[2*ia+1] - x[2*m+1];
= c*rtemp - s*itemp;
= c*itemp + s*rtemp;