The AMD-Vi support code does parse IVHD entries in IVRS table.
The entries are stored in softc->dev_cfg of the ivhd driver.
But that information is never applied to a device table.
For instance, see tables 92, 93, 94 in the AMD IOMMU specification. Those define the location of the DTE setting field in 4-byte IVHD entries and the meaning of bits in it. And then see table 7 on how those bits should be translated to bits in an actual Device Table Entry corresponding to a device described in the IVHD entry.