Use more compact representation for packed arrays.

Store just an array of zvals without keys.

Because of smaller data set, this patch may show performance improvement
on some apps and benchmarks that use packed arrays. (~1% on PHP-Parser)

The patch has a number of disadvantages:
- sapi/phpdbg needs special support for packed arrays (WATCH_ON_BUCKET).
- ZEND_HASH_FOREACH_* macros became more expensive (bigger and slower),
  because they have to support both representations (hash and packed).
  CLI PHP became 37KB bigger just because of these macros.
- zend_hash_sort_ex() may require converting packed arrays to hash.
- zend_hash_minmax() prototype was changed to compare only values.

Author: dstogov

Zend/zend_gc.c

@@ -608,28 +608,46 @@ static zend_result zend_generator_get_next_delegated_value(zend_generator *gener
 		HashTable *ht = Z_ARR(generator->values);
 		HashPosition pos = Z_FE_POS(generator->values);
 
-		Bucket *p;
-		do {
-			if (UNEXPECTED(pos >= ht->nNumUsed)) {
-				/* Reached end of array */
-				goto failure;
-			}
+		if (HT_IS_PACKED(ht)) {
+			do {
+				if (UNEXPECTED(pos >= ht->nNumUsed)) {
+					/* Reached end of array */
+					goto failure;
+				}
 
-			p = &ht->arData[pos];
-			value = &p->val;
-			pos++;
-		} while (Z_ISUNDEF_P(value));
+				value = &ht->arPacked[pos];
+				pos++;
+			} while (Z_ISUNDEF_P(value));
 
-		zval_ptr_dtor(&generator->value);
-		ZVAL_COPY(&generator->value, value);
+			zval_ptr_dtor(&generator->value);
+			ZVAL_COPY(&generator->value, value);
 
-		zval_ptr_dtor(&generator->key);
-		if (p->key) {
-			ZVAL_STR_COPY(&generator->key, p->key);
+			zval_ptr_dtor(&generator->key);
+			ZVAL_LONG(&generator->key, pos - 1);
 		} else {
-			ZVAL_LONG(&generator->key, p->h);
-		}
+			Bucket *p;
 
+			do {
+				if (UNEXPECTED(pos >= ht->nNumUsed)) {
+					/* Reached end of array */
+					goto failure;
+				}
+
+				p = &ht->arData[pos];
+				value = &p->val;
+				pos++;
+			} while (Z_ISUNDEF_P(value));
+
+			zval_ptr_dtor(&generator->value);
+			ZVAL_COPY(&generator->value, value);
+
+			zval_ptr_dtor(&generator->key);
+			if (p->key) {
+				ZVAL_STR_COPY(&generator->key, p->key);
+			} else {
+				ZVAL_LONG(&generator->key, p->h);
+			}
+		}
 		Z_FE_POS(generator->values) = pos;
 	} else {
 		zend_object_iterator *iter = (zend_object_iterator *) Z_OBJ(generator->values);