kconfig: cache expression values

Cache expression values to avoid recalculating them repeatedly.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/kconfig/confdata.c

@@ -396,6 +396,8 @@ int conf_read_simple(const char *name, int def)
 		}
 	}
 
+	expr_invalidate_all();
+
 	while (getline_stripped(&line, &line_asize, in) != -1) {
 		struct menu *choice;
 

scripts/kconfig/expr.c

@@ -887,7 +887,7 @@ static enum string_value_kind expr_parse_string(const char *str,
 	       ? kind : k_string;
 }
 
-tristate expr_calc_value(struct expr *e)
+static tristate __expr_calc_value(struct expr *e)
 {
 	tristate val1, val2;
 	const char *str1, *str2;
@@ -895,9 +895,6 @@ tristate expr_calc_value(struct expr *e)
 	union string_value lval = {}, rval = {};
 	int res;
 
-	if (!e)
-		return yes;
-
 	switch (e->type) {
 	case E_SYMBOL:
 		sym_calc_value(e->left.sym);
@@ -961,6 +958,35 @@ tristate expr_calc_value(struct expr *e)
 	}
 }
 
+/**
+ * expr_calc_value - return the tristate value of the given expression
+ * @e: expression
+ * return: tristate value of the expression
+ */
+tristate expr_calc_value(struct expr *e)
+{
+	if (!e)
+		return yes;
+
+	if (!e->val_is_valid) {
+		e->val = __expr_calc_value(e);
+		e->val_is_valid = true;
+	}
+
+	return e->val;
+}
+
+/**
+ * expr_invalidate_all - invalidate all cached expression values
+ */
+void expr_invalidate_all(void)
+{
+	struct expr *e;
+
+	hash_for_each(expr_hashtable, e, node)
+		e->val_is_valid = false;
+}
+
 static int expr_compare_type(enum expr_type t1, enum expr_type t2)
 {
 	if (t1 == t2)

scripts/kconfig/expr.h

@@ -39,12 +39,16 @@ union expr_data {
  *
  * @node:  link node for the hash table
  * @type:  expressoin type
+ * @val: calculated tristate value
+ * @val_is_valid: indicate whether the value is valid
  * @left:  left node
  * @right: right node
  */
 struct expr {
 	struct hlist_node node;
 	enum expr_type type;
+	tristate val;
+	bool val_is_valid;
 	union expr_data left, right;
 };
 

scripts/kconfig/internal.h

@@ -15,6 +15,8 @@ extern HASHTABLE_DECLARE(sym_hashtable, SYMBOL_HASHSIZE);
 
 extern HASHTABLE_DECLARE(expr_hashtable, EXPR_HASHSIZE);
 
+void expr_invalidate_all(void);
+
 struct menu;
 
 extern struct menu *current_menu, *current_entry;

scripts/kconfig/symbol.c

@@ -519,6 +519,7 @@ void sym_clear_all_valid(void)
 
 	for_all_symbols(sym)
 		sym->flags &= ~SYMBOL_VALID;
+	expr_invalidate_all();
 	conf_set_changed(true);
 	sym_calc_value(modules_sym);
 }