From a4ea2223fa701bd34b09fb3eede037908dbdd0c8 Mon Sep 17 00:00:00 2001 From: Lai Jiangshan Date: Mon, 17 Oct 2011 10:19:10 -0400 Subject: [PATCH] rculfhash: Simplify lookup_bucket() They are the same, but I don't think the compiler can optimize it. And it also helps for understanding the following code. [ Edit by Mathieu Desnoyers: - Add a comment that describes the equivalence between get_count_order and fls for this lookup of index + 1. ] Signed-off-by: Lai Jiangshan Signed-off-by: Mathieu Desnoyers --- rculfhash.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/rculfhash.c b/rculfhash.c index d733d6b..189f8c8 100644 --- a/rculfhash.c +++ b/rculfhash.c @@ -724,7 +724,12 @@ struct _cds_lfht_node *lookup_bucket(struct cds_lfht *ht, unsigned long size, assert(size > 0); index = hash & (size - 1); - order = get_count_order_ulong(index + 1); + /* + * equivalent to get_count_order_ulong(index + 1), but optimizes + * away the non-existing 0 special-case for + * get_count_order_ulong. + */ + order = fls_ulong(index); dbg_printf("lookup hash %lu index %lu order %lu aridx %lu\n", hash, index, order, index & (!order ? 0 : ((1UL << (order - 1)) - 1))); -- 2.34.1