On 24/07/18 21:34, Luc Van Oostenryck wrote:
> Sometimes it's needed to know if a list is empty, for example,
> to know if a pseudo has some users or not. Currently this is
> done using ptr_list_size() which needs to walk the whole list
> while this is often not needed if the list is empty.
Sometimes we need to know if a list is empty, for example, in
order to determine if a pseudo has some users or not. Currently,
this is done using ptr_list_size(), which always walks the whole
list. It is often possible to short-circuit this walk when the
list is empty.
(or something like that! - you may have noticed that I am not
that good at writing commit messages :D ).
>
> Add the helper ptr_list_empty() and use it for has_users().
>
> This gives a speedup up to 18% on some pathological workloads.
>
> Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
> ---
> linearize.h | 7 ++++++-
> ptrlist.c | 19 +++++++++++++++++++
> ptrlist.h | 2 ++
> simplify.c | 2 +-
> 4 files changed, 28 insertions(+), 2 deletions(-)
>
> diff --git a/linearize.h b/linearize.h
> index 092e1ac23..de42e718d 100644
> --- a/linearize.h
> +++ b/linearize.h
> @@ -333,9 +333,14 @@ static inline int pseudo_user_list_size(struct pseudo_user_list *list)
> return ptr_list_size((struct ptr_list *)list);
> }
>
> +static inline bool pseudo_user_list_empty(struct pseudo_user_list *list)
> +{
> + return ptr_list_empty((struct ptr_list *)list);
> +}
> +
> static inline int has_users(pseudo_t p)
> {
> - return pseudo_user_list_size(p->users) != 0;
> + return !pseudo_user_list_empty(p->users);
> }
>
> static inline struct pseudo_user *alloc_pseudo_user(struct instruction *insn, pseudo_t *pp)
> diff --git a/ptrlist.c b/ptrlist.c
> index 234433033..40a671000 100644
> --- a/ptrlist.c
> +++ b/ptrlist.c
> @@ -36,6 +36,25 @@ int ptr_list_size(struct ptr_list *head)
> return nr;
> }
>
> +///
> +// test if a list is empty
> +// @head: the head of the list
> +// @return: ``true`` if the list is empty, '``false`` otherwise.
extraneous ' mark just before ``false``?
ATB,
Ramsay Jones
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