From: Ursula Braun
> Sent: 19 August 2015 09:21
> In little endian cases, the macro htons unfolds to __swab16 which
> provides special case for constants. In big endian cases,
> __constant_htons and htons expand directly to the same expression.
> So, replace __constant_htons with htons with the goal of getting
> rid of the definition of __constant_htons completely.
...
> diff --git a/drivers/s390/net/qeth_l3_main.c b/drivers/s390/net/qeth_l3_main.c
> index 70eb2f6..ecfe622 100644
> --- a/drivers/s390/net/qeth_l3_main.c
> +++ b/drivers/s390/net/qeth_l3_main.c
> @@ -1887,13 +1887,13 @@ static inline int qeth_l3_rebuild_skb(struct
> qeth_card *card,
> case QETH_CAST_MULTICAST:
> switch (prot) {
> #ifdef CONFIG_QETH_IPV6
> - case __constant_htons(ETH_P_IPV6):
> + case htons(ETH_P_IPV6):
I didn't think htons() was 'constant enough' to be used as a case label.
Using byteswapped constants in a case statement can change it from being
implemented as a jump table to a branch tree.
This might be more expensive than byteswapping the value (even on systems
that don't have cheap byteswap instructions).
David
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