When I recompile a VHDL design in XST after modifying files or changing the files within the project, the following warning message occurs:
"WARNING:HDLParsers:3215 - Unit <library>/<ent | arch> is now defined in a different file: was <file1>.vhd, now is <file2>.vhd"
This message appears whenever an entity or architecture appears in a different VHDL file from the previous synthesis run. One message appears for each entity or architecture that has moved. This message indicates that XST has picked up the file change.