Texas Instruments TMS320C64X Programmer's Reference Manual page 75

Special Requirements
Implementation Notes
Benchmarks
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The number of coefficients, nh, must be a multiple of 4 and greater than
or equal to 8. Coefficients must be in reverse order.
-
The number of outputs computed, nr, must be a multiple of 4 and greater
than or equal to 4.
-
Bank Conflicts: No bank conflicts occur.
-
Interruptibility: The code is interrupt-tolerant but not interruptible.
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The load double-word instruction is used to simultaneously load four
values in a single clock cycle.
-
The inner loop is unrolled four times and will always compute a multiple
of 4 output samples.
Cycles (8 + nh) * nr/4 + 9
Codesize 308 bytes
C64x+ DSPLIB Reference
DSP_fir_r4
4-47