Improve the string descriptor.

Separate the utf-8 and ascii strings.
In case of ascii strings the size is equal to the length, so we able to store this information
in the string descriptor instead of using the string header to store it.

JerryScript-DCO-1.0-Signed-off-by: Robert Sipka rsipka.uszeged@partner.samsung.com

Author: robertsipka

jerry-core/ecma/base/ecma-globals.h

@@ -717,9 +717,9 @@ typedef struct
 typedef enum
 {
   ECMA_STRING_CONTAINER_LIT_TABLE, /**< actual data is in literal table */
-  ECMA_STRING_CONTAINER_HEAP_CHUNKS, /**< actual data is on the heap
-                                          in a ecma_collection_chunk_t chain */
+  ECMA_STRING_CONTAINER_HEAP_ASCII_STRING, /**< actual data is on the heap as an ascii string */
   ECMA_STRING_CONTAINER_HEAP_NUMBER, /**< actual data is on the heap as a ecma_number_t */
+  ECMA_STRING_CONTAINER_HEAP_UTF8_STRING, /**< actual data is on the heap as an utf-8 string */
   ECMA_STRING_CONTAINER_UINT32_IN_DESC, /**< actual data is UInt32-represeneted Number
                                              stored locally in the string's descriptor */
   ECMA_STRING_CONTAINER_MAGIC_STRING, /**< the ecma-string is equal to one of ECMA magic strings */
@@ -775,7 +775,18 @@ typedef struct ecma_string_t
     mem_cpointer_t lit_cp;
 
     /** Compressed pointer to an ecma_collection_header_t */
-    mem_cpointer_t collection_cp;
+    mem_cpointer_t utf8_collection_cp;
+
+    /**
+    * Actual data of an ascii string type
+    */
+    struct
+    {
+      /** Compressed pointer to a raw character array */
+      mem_cpointer_t ascii_collection_cp;
+      /** Size of ascii string in bytes */
+      uint16_t size;
+    } ascii_string_t;
 
     /** Compressed pointer to an ecma_number_t */
     mem_cpointer_t number_cp;