When transforming or funneling from a Virtex-6 IODELAYE1 primitive to a Kintex-7 IDELAYE2 primitive, the value of IDELAY_TYPE is being dropped.
The Virtex-6 IODELAYE1 primitive has a property named IDELAY_TYPE which has value of "VAR_LOADABLE".
The Kintex-7 IDELAYE2 primitive also has a property named IDELAY_TYPE but "VAR_LOADABLE" is not a legal value.
The value in Kintex-7 should be "VAR_LOAD" or "VAR_LOAD_PIPE".
When synthesizing a design with a Virtex-6 IODELAYE1 primitive instantiated with IDELAY_TYPE set to "VAR_LOADABLE", Vivado is dropping the IDELAY_TYPE during the transform to the Kintex-7 IDELAYE2.
This leads to a CRITICAL WARNING when trying to open the Synthesized Design in Vivado.
This issue has been resolved in Vivado Design Suite 2012.4.