Sixteen bit hash for strings.

JerryScript-DCO-1.0-Signed-off-by: Zoltan Herczeg zherczeg.u-szeged@partner.samsung.com

jerry-core/ecma/base/ecma-helpers-string.c

@@ -1286,7 +1286,6 @@ ecma_is_string_magic (const ecma_string_t *string_p, /**< ecma-string */
  */
 lit_string_hash_t
 ecma_string_hash (const ecma_string_t *string_p) /**< ecma-string to calculate hash for */
-
 {
   return (string_p->hash);
 } /* ecma_string_hash */

jerry-core/ecma/base/ecma-property-hashmap.c

@@ -124,13 +124,13 @@ ecma_property_hashmap_create (ecma_object_t *object_p) /**< object */
 
   uint8_t shift_counter = 0;
 
-  if (max_property_count <= (1u << LIT_STRING_HASH_BITS))
+  if (max_property_count <= LIT_STRING_HASH_LIMIT)
   {
     hashmap_p->header.types[1].type_and_flags = 0;
   }
   else
   {
-    while (max_property_count > (1u << LIT_STRING_HASH_BITS))
+    while (max_property_count > LIT_STRING_HASH_LIMIT)
     {
       shift_counter++;
       max_property_count >>= 1;
@@ -162,7 +162,7 @@ ecma_property_hashmap_create (ecma_object_t *object_p) /**< object */
       uint32_t entry_index = name_p->hash;
       uint32_t step = ecma_property_hashmap_steps[entry_index & (ECMA_PROPERTY_HASHMAP_NUMBER_OF_STEPS - 1)];
 
-      if (mask < (1u << LIT_STRING_HASH_BITS))
+      if (mask < LIT_STRING_HASH_LIMIT)
       {
         entry_index &= mask;
       }
@@ -261,7 +261,7 @@ ecma_property_hashmap_insert (ecma_object_t *object_p, /**< object */
   uint32_t step = ecma_property_hashmap_steps[entry_index & (ECMA_PROPERTY_HASHMAP_NUMBER_OF_STEPS - 1)];
   uint32_t mask = hashmap_p->max_property_count - 1;
 
-  if (mask < (1u << LIT_STRING_HASH_BITS))
+  if (mask < LIT_STRING_HASH_LIMIT)
   {
     entry_index &= mask;
   }
@@ -336,7 +336,7 @@ ecma_property_hashmap_delete (ecma_object_t *object_p, /**< object */
   jmem_cpointer_t *pair_list_p = (jmem_cpointer_t *) (hashmap_p + 1);
   uint8_t *bits_p = (uint8_t *) (pair_list_p + hashmap_p->max_property_count);
 
-  if (mask < (1u << LIT_STRING_HASH_BITS))
+  if (mask < LIT_STRING_HASH_LIMIT)
   {
     entry_index &= mask;
   }
@@ -446,7 +446,7 @@ ecma_property_hashmap_find (ecma_property_hashmap_t *hashmap_p, /**< hashmap */
   jmem_cpointer_t *pair_list_p = (jmem_cpointer_t *) (hashmap_p + 1);
   uint8_t *bits_p = (uint8_t *) (pair_list_p + hashmap_p->max_property_count);
 
-  if (mask < (1u << LIT_STRING_HASH_BITS))
+  if (mask < LIT_STRING_HASH_LIMIT)
   {
     entry_index &= mask;
   }

jerry-core/ecma/operations/ecma-objects.c

@@ -31,6 +31,11 @@
  * @{
  */
 
+/**
+ * Hash bitmap size for ecma objects
+ */
+#define ECMA_OBJECT_HASH_BITMAP_SIZE 256
+
 /**
  * Assert that specified object type value is valid
  *
@@ -48,6 +53,7 @@
 #else /* JERRY_NDEBUG */
 #define JERRY_ASSERT_OBJECT_TYPE_IS_VALID(type)
 #endif /* !JERRY_NDEBUG */
+
 /**
  * [[Get]] ecma object's operation
  *
@@ -483,7 +489,7 @@ ecma_op_object_is_prototype_of (ecma_object_t *base_p, /**< base object */
  *
  * Order of names in the collection:
  *  - integer indices in ascending order
- *  - other indices in creation order (for built-ins - in the order the properties are listed in specification).
+ *  - other indices in creation order (for built-ins: the order of the properties are listed in specification).
  *
  * Note:
  *      Implementation of the routine assumes that new properties are appended to beginning of corresponding object's
@@ -510,7 +516,7 @@ ecma_op_object_get_property_names (ecma_object_t *obj_p, /**< object */
   const bool obj_is_builtin = ecma_get_object_is_builtin (obj_p);
 
   const size_t bitmap_row_size = sizeof (uint32_t) * JERRY_BITSINBYTE;
-  uint32_t names_hashes_bitmap[(1u << LIT_STRING_HASH_BITS) / bitmap_row_size];
+  uint32_t names_hashes_bitmap[ECMA_OBJECT_HASH_BITMAP_SIZE / bitmap_row_size];
 
   memset (names_hashes_bitmap, 0, sizeof (names_hashes_bitmap));
 
@@ -571,14 +577,14 @@ ecma_op_object_get_property_names (ecma_object_t *obj_p, /**< object */
     ecma_collection_iterator_t iter;
     ecma_collection_iterator_init (&iter, prop_names_p);
 
-    uint32_t own_names_hashes_bitmap[(1u << LIT_STRING_HASH_BITS) / bitmap_row_size];
+    uint32_t own_names_hashes_bitmap[ECMA_OBJECT_HASH_BITMAP_SIZE / bitmap_row_size];
     memset (own_names_hashes_bitmap, 0, sizeof (own_names_hashes_bitmap));
 
     while (ecma_collection_iterator_next (&iter))
     {
       ecma_string_t *name_p = ecma_get_string_from_value (*iter.current_value_p);
 
-      lit_string_hash_t hash = name_p->hash;
+      uint8_t hash = (uint8_t) name_p->hash;
       uint32_t bitmap_row = (uint32_t) (hash / bitmap_row_size);
       uint32_t bitmap_column = (uint32_t) (hash % bitmap_row_size);
 
@@ -613,7 +619,7 @@ ecma_op_object_get_property_names (ecma_object_t *obj_p, /**< object */
 
           if (!(is_enumerable_only && !ecma_is_property_enumerable (property_p)))
           {
-            lit_string_hash_t hash = name_p->hash;
+            uint8_t hash = (uint8_t) name_p->hash;
             uint32_t bitmap_row = (uint32_t) (hash / bitmap_row_size);
             uint32_t bitmap_column = (uint32_t) (hash % bitmap_row_size);
 
@@ -652,7 +658,7 @@ ecma_op_object_get_property_names (ecma_object_t *obj_p, /**< object */
                                               ecma_make_string_value (name_p),
                                               true);
 
-            lit_string_hash_t hash = name_p->hash;
+            uint8_t hash = (uint8_t) name_p->hash;
             uint32_t bitmap_row = (uint32_t) (hash / bitmap_row_size);
             uint32_t bitmap_column = (uint32_t) (hash % bitmap_row_size);
 
@@ -771,7 +777,7 @@ ecma_op_object_get_property_names (ecma_object_t *obj_p, /**< object */
 
       ecma_string_t *name_p = names_p[i];
 
-      lit_string_hash_t hash = name_p->hash;
+      uint8_t hash = (uint8_t) name_p->hash;
       uint32_t bitmap_row = (uint32_t) (hash / bitmap_row_size);
       uint32_t bitmap_column = (uint32_t) (hash % bitmap_row_size);
 

jerry-core/lit/lit-globals.h

@@ -126,11 +126,16 @@ typedef uint32_t lit_code_point_t;
 /**
  * ECMA string hash
  */
-typedef uint8_t lit_string_hash_t;
+typedef uint16_t lit_string_hash_t;
 
 /**
- * ECMA string hash value length, in bits
+ * Maximum value of ECMA string hash + 1
+ *
+ * Note:
+ *   On ARM, this constant can be encoded as an immediate value
+ *   while 0xffffu cannot be. Hence using this constant reduces
+ *   binary size and improves performance.
  */
-#define LIT_STRING_HASH_BITS (sizeof (lit_string_hash_t) * JERRY_BITSINBYTE)
+#define LIT_STRING_HASH_LIMIT 0x10000u
 
 #endif /* !LIT_GLOBALS_H */