Re: [lwip-devel] Checksum optimizations

[Andrey Volkov]

Hello Bill!

Bill Auerbach wrote:
> In the inet_chksum.c code, there are 6 occurrences of:
>
>  
>
>     while ((acc >> 16) != 0) {
>
>       acc = (acc & 0xffffUL) + (acc >> 16);
>
>     }
>
>  
>
> Is it not true that the loop can run a maximum of once?  Wouldn’t this 
> be slightly more efficient?
>
>  
>
>     if ((acc >> 16) != 0) {
>
>       acc = (acc & 0xffffUL) + 1;
>
>     }
>
>  
IHMO, next code will be better, since "if" usually more expensive then 
arithmetic instructions.

acc = (acc & 0xffff) + (acc >> 16);


--
Regards
Andrey Volkov