Merge branch 'nd/attr-optim'

Optimize attribute look-up, mostly useful in "git grep" on a
project that does not use many attributes, by avoiding it when we
(should) know that the attributes are not defined in the first
place.

* nd/attr-optim:
  attr: avoid heavy work when we know the specified attr is not defined
  attr: do not attempt to expand when we know it's not a macro
  attr.c: rename arg name attr_nr to avoid shadowing the global one

Author: gitster

attr.c

@@ -32,9 +32,12 @@ struct git_attr {
 	struct git_attr *next;
 	unsigned h;
 	int attr_nr;
+	int maybe_macro;
+	int maybe_real;
 	char name[FLEX_ARRAY];
 };
 static int attr_nr;
+static int cannot_trust_maybe_real;
 
 static struct git_attr_check *check_all_attr;
 static struct git_attr *(git_attr_hash[HASHSIZE]);
@@ -95,6 +98,8 @@ 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;
+	a->maybe_real = 0;
 	git_attr_hash[pos] = a;
 
 	REALLOC_ARRAY(check_all_attr, attr_nr);
@@ -244,9 +249,10 @@ 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;
@@ -266,6 +272,10 @@ static struct match_attr *parse_attr_line(const char *line, const char *src,
 	/* Second pass to fill the attr_states */
 	for (cp = states, i = 0; *cp; i++) {
 		cp = parse_attr(src, lineno, cp, &(res->state[i]));
+		if (!is_macro)
+			res->state[i].attr->maybe_real = 1;
+		if (res->state[i].attr->maybe_macro)
+			cannot_trust_maybe_real = 1;
 	}
 
 	return res;
@@ -681,21 +691,22 @@ static int fill(const char *path, int pathlen, int basename_offset,
 	return rem;
 }
 
-static int macroexpand_one(int attr_nr, int rem)
+static int macroexpand_one(int nr, int rem)
 {
 	struct attr_stack *stk;
 	struct match_attr *a = NULL;
 	int i;
 
-	if (check_all_attr[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)
 		for (i = stk->num_matches - 1; !a && 0 <= i; i--) {
 			struct match_attr *ma = stk->attrs[i];
 			if (!ma->is_macro)
 				continue;
-			if (ma->u.attr->attr_nr == attr_nr)
+			if (ma->u.attr->attr_nr == nr)
 				a = ma;
 		}
 
@@ -706,10 +717,13 @@ static int macroexpand_one(int attr_nr, int rem)
 }
 
 /*
- * Collect all attributes for path into the array pointed to by
- * check_all_attr.
+ * Collect attributes for path into the array pointed to by
+ * check_all_attr. If num is non-zero, only attributes in check[] are
+ * collected. Otherwise all attributes are collected.
  */
-static void collect_all_attrs(const char *path)
+static void collect_some_attrs(const char *path, int num,
+			       struct git_attr_check *check)
+
 {
 	struct attr_stack *stk;
 	int i, pathlen, rem, dirlen;
@@ -732,6 +746,19 @@ static void collect_all_attrs(const char *path)
 	prepare_attr_stack(path, dirlen);
 	for (i = 0; i < attr_nr; i++)
 		check_all_attr[i].value = ATTR__UNKNOWN;
+	if (num && !cannot_trust_maybe_real) {
+		rem = 0;
+		for (i = 0; i < num; i++) {
+			if (!check[i].attr->maybe_real) {
+				struct git_attr_check *c;
+				c = check_all_attr + check[i].attr->attr_nr;
+				c->value = ATTR__UNSET;
+				rem++;
+			}
+		}
+		if (rem == num)
+			return;
+	}
 
 	rem = attr_nr;
 	for (stk = attr_stack; 0 < rem && stk; stk = stk->prev)
@@ -742,7 +769,7 @@ int git_check_attr(const char *path, int num, struct git_attr_check *check)
 {
 	int i;
 
-	collect_all_attrs(path);
+	collect_some_attrs(path, num, check);
 
 	for (i = 0; i < num; i++) {
 		const char *value = check_all_attr[check[i].attr->attr_nr].value;
@@ -758,7 +785,7 @@ int git_all_attrs(const char *path, int *num, struct git_attr_check **check)
 {
 	int i, count, j;
 
-	collect_all_attrs(path);
+	collect_some_attrs(path, 0, NULL);
 
 	/* Count the number of attributes that are set. */
 	count = 0;