Texas Instruments TMS320C64X Programmer's Reference Manual page 107

Special Requirements
Implementation Notes
Benchmarks
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Input and output arrays do not overlap, except when "r == NULL" so that
the operation occurs in-place.
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The input array and output array are expected to be double-word aligned,
and a multiple of 8 half-words must be processed.
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Bank Conflicts: No bank conflicts occur.
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Interruptibility: The code is interrupt-tolerant but not interruptible.
Cycles nx/8 + 18
Codesize 104 bytes
DSP_blk_eswap16
C64x+ DSPLIB Reference 4-79