netdev - RE: [PATCH] igb: Convert a series of if statements to switch case

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Date:   Thu, 12 May 2022 13:14:05 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'xiaolinkui' <xiaolinkui@...il.com>,
        "pmenzel@...gen.mpg.de" <pmenzel@...gen.mpg.de>,
        "jesse.brandeburg@...el.com" <jesse.brandeburg@...el.com>,
        "anthony.l.nguyen@...el.com" <anthony.l.nguyen@...el.com>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Linkui Xiao <xiaolinkui@...inos.cn>
Subject: RE: [PATCH] igb: Convert a series of if statements to switch case

> From: Linkui Xiao <xiaolinkui@...inos.cn>
>
> Convert a series of if statements that handle different events to a switch
> case statement to simplify the code.
>
> V2: fix patch description and email format.
>
> Signed-off-by: Linkui Xiao <xiaolinkui@...inos.cn>
> ---
>  drivers/net/ethernet/intel/igb/igb_main.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
> index 34b33b21e0dc..4ce0718eeff6 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -4588,13 +4588,17 @@ static inline void igb_set_vf_vlan_strip(struct igb_adapter *adapter,
>       struct e1000_hw *hw = &adapter->hw;
>       u32 val, reg;
>
> -     if (hw->mac.type < e1000_82576)
> +     switch (hw->mac.type) {
> +     case e1000_undefined:
> +     case e1000_82575:
>               return;
> -
> -     if (hw->mac.type == e1000_i350)
> +     case e1000_i350:
>               reg = E1000_DVMOLR(vfn);
> -     else
> +             break;
> +     default:
>               reg = E1000_VMOLR(vfn);
> +             break;
> +     }
>
>       val = rd32(reg);
>       if (enable)
> --
> 2.17.1

Are you sure that generates reasonable code?
The compiler could generate something completely different
for the two versions.

It isn't even obvious they are equivalent.

	David

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