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DSP_r4fft
4-97 C64x+ DSPLIB Reference
>>15;
x[2 * i3 + 1] = (s2 * co3−r2 *
si3)>>15;
}
}
ie <<= 2;
}
}
Special Requirements
- 4 ≤ nx ≤ 65536 (nx a power of 4)
- x is aligned on a 4*nx byte boundary for circular buffering
- Input x and coefficients w should be in different data sections or memory
spaces to eliminate memory bank hits. If this is not possible, w should be
aligned on an odd word boundary to minimize memory bank hits
- x data is stored in the order real[0], image[0], real[1], ...
- The FFT coefficients (twiddle factors) are generated using the program
tw_r4fft provided in the directory ‘support\fft’.
Implementation Notes
- Bank Conflicts: See Benchmarks.
- Interruptibility: The code is interrupt-tolerant but not interruptible.
- Loads input x and coefficient w as words.
- Both loops j and i0 shown in the C code are placed in the INNERLOOP of
the assembly code.
Benchmarks The performance of this function has not yet been characterized on the C64x+.