[v3 PATCH 2/9] rhashtable: Eliminate unnecessary branch in rht_key_hashfn
From: Herbert Xu <herbert@gondor.apana.org.au>
Date: 2015-03-23 13:50:41
Subsystem:
rhashtable, the rest · Maintainers:
Thomas Graf, Herbert Xu, Linus Torvalds
When rht_key_hashfn is called from rhashtable itself and params is equal to ht->p, there is no point in checking params.key_len and falling back to ht->p.key_len. For some reason gcc couldn't figure out that params is the same as ht->p. So let's help it by only checking params.key_len when it's a constant. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> --- include/linux/rhashtable.h | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h
index 18a6488..e316f10 100644
--- a/include/linux/rhashtable.h
+++ b/include/linux/rhashtable.h@@ -199,8 +199,12 @@ static inline unsigned int rht_key_hashfn( struct rhashtable *ht, const struct bucket_table *tbl, const void *key, const struct rhashtable_params params) { - return rht_bucket_index(tbl, params.hashfn(key, params.key_len ?: - ht->p.key_len, + /* params must be equal to ht->p if it isn't constant. */ + unsigned key_len = __builtin_constant_p(params.key_len) ? + (params.key_len ?: ht->p.key_len) : + params.key_len; + + return rht_bucket_index(tbl, params.hashfn(key, key_len, tbl->hash_rnd)); }