Re: [PATCH/RFC 3/4] attr: do not attempt to expand when we know it's not a macro

[Junio C Hamano <gitster@pobox.com>]

Nguyễn Thái Ngọc Duy  <pclouds@gmail.com> writes:

> Keep track of all recognized macros in the new "maybe_macro" field.
> This this field is true, it _may_ be a macro (depending on what's in
> the current attr stack). But if the field is false, it's definitely
> not a macro, no need to go through the whole attr stack in
> macroexpand_one() to search for one.
>
> Without this, "git grep abcdefghi" on git.git hits the inner loop in
> macroexpand_one() about 2500 times. With this, it's about 60 times.

Nice ;-)

>
> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
> ---
>  attr.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/attr.c b/attr.c
> index def09c7..4ec6186 100644
> --- a/attr.c
> +++ b/attr.c
> @@ -32,6 +32,7 @@ struct git_attr {
>  	struct git_attr *next;
>  	unsigned h;
>  	int attr_nr;
> +	int maybe_macro;
>  	char name[FLEX_ARRAY];
>  };
>  static int git_attr_nr;
> @@ -95,6 +96,7 @@ static struct git_attr *git_attr_internal(const char *name, int len)
>  	a->h = hval;
>  	a->next = git_attr_hash[pos];
>  	a->attr_nr = git_attr_nr++;
> +	a->maybe_macro = 0;
>  	git_attr_hash[pos] = a;
>  
>  	REALLOC_ARRAY(check_all_attr, git_attr_nr);
> @@ -244,9 +246,10 @@ static struct match_attr *parse_attr_line(const char *line, const char *src,
>  		      sizeof(*res) +
>  		      sizeof(struct attr_state) * num_attr +
>  		      (is_macro ? 0 : namelen + 1));
> -	if (is_macro)
> +	if (is_macro) {
>  		res->u.attr = git_attr_internal(name, namelen);
> -	else {
> +		res->u.attr->maybe_macro = 1;
> +	} else {
>  		char *p = (char *)&(res->state[num_attr]);
>  		memcpy(p, name, namelen);
>  		res->u.pat.pattern = p;
> @@ -687,7 +690,8 @@ static int macroexpand_one(int attr_nr, int rem)
>  	struct match_attr *a = NULL;
>  	int i;
>  
> -	if (check_all_attr[attr_nr].value != ATTR__TRUE)
> +	if (check_all_attr[attr_nr].value != ATTR__TRUE ||
> +	    !check_all_attr[attr_nr].attr->maybe_macro)
>  		return rem;
>  
>  	for (stk = attr_stack; !a && stk; stk = stk->prev)