Inferring Shift Registers - 2021.1 English

Vitis HLS will now infer a shift register when encountering the following code:

int A[N]; // This will be replaced by a shift register
 
for(...) {
  // The loop below is the shift operation
  for (int i = 0; i < N-1; ++i)
    A[i] = A[i+1];
  A[N] = ...;
 
  // This is an access to the shift register
  ... A[x] ...
}

Shift registers can perform a shift/cycle, which offers a significant performance improvement, and also allows a random read access per cycle anywhere in the shift register, thus it is more flexible than a FIFO.