I received the following DRC warning during bitstream generation:
The message is repeated for LUT pin 'A3' and 'A4'.
What does this DRC message mean and does this issue affect functionality?
The DRC check is intended to verify that the LUT configuration is consistent with its connectivity. In this example the DRC message is invalid.
The LUT6_2 is a macro containing both a LUT5 and a LUT6. While it is true that the equation of the O5 LUT does not use all input pins, the O6 LUT uses all of the input pins and so the configuration is valid.
This issue has been fixed in Vivado 2016.3, and this incorrect DRC warning no longer occurs.