Analog Devices ADSP-BF53x Blackfin Reference page 554

Instruction Overview
Also See
Modify – Decrement, Add,
Special Applications
Typically, use the Index Register and Pointer Register versions of the
Modify – Increment instruction to increment indirect address pointers for
load or store operations.
15-42 ADSP-BF53x/BF56x Blackfin Processor Programming Reference
Shift with Add