Buffer Recompute After Unrolling

[mattfel1]

Sometimes the buffer info is wrong after unrolling, in a case like:

Foreach(N by 1){i => 
  Foreach(0 until 1 by 1){j =>
    ... = mux(j == 0, ..., mem(i)
  }
  Pipe{mem(i) = ...}
}
... = mem(i)

mem will get double buffered before unrolling but then the mux will be deleted when the Foreach turns into a unit pipe

This partially or fully accounts for the bug mentioned in #84