Use a BOP for Hash#default

On a hash miss we need to call default if it is redefined in order to
return the default value to be used. Previously we checked this with
rb_method_basic_definition_p, which avoids the method call but requires
a method lookup.

This commit replaces the previous check with BASIC_OP_UNREDEFINED_P and
a new BOP_DEFAULT. We still need to fall back to
rb_method_basic_definition_p when called on a subclasss of hash.

    |                |compare-ruby|built-ruby|
    |:---------------|-----------:|---------:|
    |hash_aref_miss  |       2.692|     3.531|
    |                |           -|     1.31x|

Co-authored-by: Daniel Colson <danieljamescolson@gmail.com>
Co-authored-by: "Ian C. Anderson" <ian@iancanderson.com>
Co-authored-by: Jack McCracken <me@jackmc.xyz>

1 files changed, 17 insertions, 3 deletions

diff --git a/hash.c b/hash.c
index a577e77985..1923c63eb3 100644
--- a/hash.c
+++ b/hash.c
@@ -28,6 +28,7 @@
 #include "internal.h"
 #include "internal/array.h"
 #include "internal/bignum.h"
+#include "internal/basic_operators.h"
 #include "internal/class.h"
 #include "internal/cont.h"
 #include "internal/error.h"
@@ -93,9 +94,11 @@ rb_hash_freeze(VALUE hash)
 VALUE rb_cHash;
 
 static VALUE envtbl;
-static ID id_hash, id_default, id_flatten_bang;
+static ID id_hash, id_flatten_bang;
 static ID id_hash_iter_lev;
 
+#define id_default idDefault
+
 VALUE
 rb_hash_set_ifnone(VALUE hash, VALUE ifnone)
 {
@@ -2070,10 +2073,22 @@ call_default_proc(VALUE proc, VALUE hash, VALUE key)
     return rb_proc_call_with_block(proc, 2, args, Qnil);
 }
 
+static bool
+rb_hash_default_unredefined(VALUE hash)
+{
+    VALUE klass = RBASIC_CLASS(hash);
+    if (LIKELY(klass == rb_cHash)) {
+        return !!BASIC_OP_UNREDEFINED_P(BOP_DEFAULT, HASH_REDEFINED_OP_FLAG);
+    }
+    else {
+        return LIKELY(rb_method_basic_definition_p(klass, id_default));
+    }
+}
+
 VALUE
 rb_hash_default_value(VALUE hash, VALUE key)
 {
-    if (LIKELY(rb_method_basic_definition_p(CLASS_OF(hash), id_default))) {
+    if (LIKELY(rb_hash_default_unredefined(hash))) {
         VALUE ifnone = RHASH_IFNONE(hash);
         if (!FL_TEST(hash, RHASH_PROC_DEFAULT)) return ifnone;
         if (UNDEF_P(key)) return Qnil;
@@ -7164,7 +7179,6 @@ void
 Init_Hash(void)
 {
     id_hash = rb_intern_const("hash");
-    id_default = rb_intern_const("default");
     id_flatten_bang = rb_intern_const("flatten!");
     id_hash_iter_lev = rb_make_internal_id();