Optimize calls to `Kernel#hash` (#3987)

This avoids recursive checks when the `hash` method of an object
isn't specialized.

1 files changed, 5 insertions, 1 deletions

diff --git a/hash.c b/hash.c
index 9b4c315a09..c3a512b8e9 100644
--- a/hash.c
+++ b/hash.c
@@ -142,7 +142,11 @@ hash_recursive(VALUE obj, VALUE arg, int recurse)
 VALUE
 rb_hash(VALUE obj)
 {
-    VALUE hval = rb_exec_recursive_outer(hash_recursive, obj, 0);
+    VALUE hval = rb_check_funcall_basic_kw(obj, id_hash, rb_mKernel, 0, 0, 0);
+
+    if (hval == Qundef) {
+	hval = rb_exec_recursive_outer(hash_recursive, obj, 0);
+    }
 
     while (!FIXNUM_P(hval)) {
         if (RB_TYPE_P(hval, T_BIGNUM)) {