How does the Spartan-6 FPGA 9K block RAM initialization issue described in (Xilinx Answer 39999) affect the LogiCOREIP FIFO Generator?
The FIFO Generator IP core uses 9K block RAM in some configurations. A MAP and BitGen DRC warning is issued if your configuration uses the RAMB8BWER.
Because the FIFO Generator cannot be initialized and is always written to before it has a valid output, the warning can be safely ignored.
For a detailed list of LogiCOREIPFIFO Generator Release Notes and Known Issues, see (Xilinx Answer 40592).