General Description: Beginning with Synopsys Compiler version 1999.05, the following warning may be seen while reading in library files specified by the "SYNLIBS" program:
Warning: The following synthetic libraries should be added to the list of link libraries: 'xdw_spartanxl'. (UISN-26)
The library listed is in .sldb format and is normally listed only in the synthetic_library listing.
Solution
According to Synopsys, this warning can be safely ignored. However, to make the warning disappear, simply add the specified .sldb synthetic library to the link_library listing. For a Spartan-XL device, your libraries would look like this: