On C7x, LHT operations are controlled by a handful of control registers. C7x supports up to 4 table configurations that can be simultaneously active. On VCOP only one table operation can be active at a time so the migration tool always uses configuration 0 for the LHT operation. This configuration is enabled by writing __LUT_ENABLE_0 into the LTER register and configured via the LTBR0 and LTCR0 control registers. The LTBR specifies the base of the configured table in L1D. Since there is only one active table the migration tool always establishes the base address at 0, and allocates all 32K bytes for configuration 0.

The LTCR configuration specifies table properties such as number of parallel tables, element size and signedness, element promotion, and saturation behavior (for histogram). The migration tool configures these fields according to the properties of the VCOP table. Elements are always promoted to 32-bits since that’s how translated vectors are modeled.

The table configuration is computed by the LHT_base::config() method. The migration tool generates a call to this method in the kernel init() function and stores the config value in the tvals structure. Then, in the vloops() function, the migration tool generates a call to LHT_base::open(), which copies the config value from the tvals structure into LTCR0, thereby configuring the table.