So when you say primitive components, are you talking about directly manipulating the components in a logic block (https://www.xilinx.com/support/documentation/user_guides/ug3...), or do you just mean the abstractions above that like "blockram", "LUT6", "shift register"?
Because you can do a lot more with an FPGA's logic blocks than indicated by those higher level abstractions.
The relevant documents here are the "Virtex-6 Libraries Guide for HDL Designs" and "… for Schematic Designs". (There are similar documents for other part families.) These document all primitives available in the Virtex-6 family, including:
• Individual LUTs, with optional local or dual outputs (LUT1, LUT1_L, LUT1_D, … LUT6, LUT6_L, LUT6_D)
• Flip-flops (FDCE, FDRE, etc)
• The carry chain, which can be instantiated directly (CARRY4), or as its individual elements (MUXCY, XORCY)
• Shift registers implemented in LUTs (SRL16E, SRLC32E)
