attr: do not attempt to expand when we know it's not a macro

Keep track of all recognized macros in the new "maybe_macro" field.
If 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() 2481 times. With this, it's 66 times.

Helped-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/attr.c b/attr.c
index a1758bf537d09d77ad730ca2f2b928b4190d292c..b80e52b157de61f1d4a22d730e2a9c1cb88caaba 100644 (file)
--- 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 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 = attr_nr++;
+       a->maybe_macro = 0;
        git_attr_hash[pos] = a;
 
        REALLOC_ARRAY(check_all_attr, 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 nr, int rem)
        struct match_attr *a = NULL;
        int i;
 
-       if (check_all_attr[nr].value != ATTR__TRUE)
+       if (check_all_attr[nr].value != ATTR__TRUE ||
+           !check_all_attr[nr].attr->maybe_macro)
                return rem;
 
        for (stk = attr_stack; !a && stk; stk = stk->prev)