Re: [lwip-devel] Checksum optimizations

[address@hidden]

Bill Auerbach wrote:
> Additionally:
>
>  
>
> u16_t
>
> inet_chksum(void *dataptr, u16_t len)
>
> {
>
>   u32_t acc;
>
>  
>
>   acc = LWIP_CHKSUM(dataptr, len);
>
>   while ((acc >> 16) != 0) {
>
>     acc = (acc & 0xffff) + (acc >> 16);
>
>   }
>
>   return (u16_t)~(acc & 0xffff);
>
> }
>
>  
>
> Can be:
>
>  
>
> u16_t
>
> inet_chksum(void *dataptr, u16_t len)
>
> {
>
>   u32_t acc;
>
>  
>
>   acc = LWIP_CHKSUM(dataptr, len);
>
>   return (u16_t)~(acc & 0xffff);
>
> }
>
>  
>
> Because LWIP_CHKSUM returns a u16_t and thus the while loop can never 
> execute.
>
>  
So the whole function can be effectively optimized away using:
#define inet_chksum(x,y) ~LWIP_CHKSUM(x,y)
?


Simon