On 10/14/2011 10:25 PM, Mathieu Desnoyers wrote: > * Lai Jiangshan ([email protected]) wrote: >> They are the same, but I don't think the compiler >> can optimize it. > > Can you double-check this by comparing assembly output ? > >> >> And it also helps for understanding the following code. > > I try to use "get_count_order" in the algorithms everywhere so we have > only a single semantic to keep in mind.
The algorithm uses the highest bit's order for order array index. The algorithm drops the highest bit for aridx, I think fls_ulong()'s semantic matchs "the highest bit" mostly. Thanks Lai > > Thanks, > > Mathieu > >> >> Signed-off-by: Lai Jiangshan <[email protected]> >> --- >> rculfhash.c | 2 +- >> 1 files changed, 1 insertions(+), 1 deletions(-) >> >> diff --git a/rculfhash.c b/rculfhash.c >> index edbd24a..7b880d7 100644 >> --- a/rculfhash.c >> +++ b/rculfhash.c >> @@ -719,7 +719,7 @@ 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); >> + 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))); >> -- >> 1.7.4.4 >> > _______________________________________________ ltt-dev mailing list [email protected] http://lists.casi.polymtl.ca/cgi-bin/mailman/listinfo/ltt-dev
