IGC_IVAR0
ivar = IGC_READ_REG_ARRAY(hw, IGC_IVAR0, index);
IGC_WRITE_REG_ARRAY(hw, IGC_IVAR0, index, ivar);
ivar = IGC_READ_REG_ARRAY(hw, IGC_IVAR0, index);
IGC_WRITE_REG_ARRAY(hw, IGC_IVAR0, index, ivar);