RE: [PATCH net-next 06/12] qlcnic: Convert nested if-else to switch-case
From: David Laight <hidden>
Date: 2013-05-24 08:42:43
-
- if (priv_level == QLCNIC_NON_PRIV_FUNC) {
+ switch (priv_level) {
+ case QLCNIC_NON_PRIV_FUNC:
ahw->op_mode = QLCNIC_NON_PRIV_FUNC;
ahw->idc.state_entry = qlcnic_83xx_idc_ready_state_entry;
nic_ops->init_driver = qlcnic_83xx_init_non_privileged_vnic;
- } else if (priv_level == QLCNIC_PRIV_FUNC) {
+ break;
+ case QLCNIC_PRIV_FUNC:
ahw->op_mode = QLCNIC_PRIV_FUNC;
ahw->idc.state_entry = qlcnic_83xx_idc_vnic_pf_entry;
nic_ops->init_driver = qlcnic_83xx_init_privileged_vnic;
- } else if (priv_level == QLCNIC_MGMT_FUNC) {
+ break;
+ case QLCNIC_MGMT_FUNC:
ahw->op_mode = QLCNIC_MGMT_FUNC;
ahw->idc.state_entry = qlcnic_83xx_idc_ready_state_entry;
nic_ops->init_driver = qlcnic_83xx_init_mgmt_vnic;
- } else {
+ break;
+ default:
+ dev_err(&adapter->pdev->dev, "Invalid Virtual NIC opmode\n");
return -EIO;
}If the NON_PRIV case happens most of the time, then the old code would have a single conditional branch that could easily be predicted correctly. The switch statement version will either be a compare and an indirect jump (a pipeline stall on a lot of cpus) or a compare-branch chain. So this is necessarily an improvent! David