ko1	2019-01-04 16:49:00 +0900 (Fri, 04 Jan 2019)

  New Revision: 66702

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=66702

  Log:
    skip to calculate hash value on empty Hash ar_table lookup.
    
    * hash.c (ar_lookup): don't calculate hash_value if ar_table is empty.

  Modified files:
    trunk/hash.c
Index: hash.c
===================================================================
--- hash.c	(revision 66701)
+++ hash.c	(revision 66702)
@@ -928,18 +928,23 @@ ar_insert(VALUE hash, st_data_t key, st_ https://github.com/ruby/ruby/blob/trunk/hash.c#L928
 static int
 ar_lookup(VALUE hash, st_data_t key, st_data_t *value)
 {
-    st_hash_t hash_value = do_hash(key);
-    unsigned bin = find_entry(hash, hash_value, key);
-
-    if (bin == RHASH_AR_TABLE_MAX_BOUND) {
+    if (RHASH_AR_TABLE_SIZE(hash) == 0) {
         return 0;
     }
     else {
-        HASH_ASSERT(bin < RHASH_AR_TABLE_MAX_BOUND);
-        if (value != NULL) {
-            *value = RHASH_AR_TABLE_REF(hash, bin)->record;
+        st_hash_t hash_value = do_hash(key);
+        unsigned bin = find_entry(hash, hash_value, key);
+
+        if (bin == RHASH_AR_TABLE_MAX_BOUND) {
+            return 0;
+        }
+        else {
+            HASH_ASSERT(bin < RHASH_AR_TABLE_MAX_BOUND);
+            if (value != NULL) {
+                *value = RHASH_AR_TABLE_REF(hash, bin)->record;
+            }
+            return 1;
         }
-        return 1;
     }
 }
 

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