You are using a deprecated Browser. Internet Explorer is no longer supported by Xilinx.
1.5i Virtex Map - RLOCs cannot be applied to SRL16s
Keywords: SRL16, RLOC
RLOC or LOCing SR16 with other logic, such as flops into the same
slice is not supported in the 1.5i release.
In the 2.1i release, the mapper will support this feature. The 1.5i
workaround is to use a hard macro.