In one disclosed embodiment, a processor includes a first execution unit and a second execution unit, a register file, and a data path including a plurality of lanes. The data path and the register file are arranged so that writing to the register file by the first execution unit and by the second execution unit is allowed over the data path, reading from the register file by the first execution unit is allowed over the data path, and reading from the register file by the second execution unit is not allowed over the data path. The processor also includes a power control circuit configured to, when a transfer of data between the register file and either of the first and second execution units uses less than all of the lanes, power down the lanes of the data path not used for the transfer of the data.