State cache and other performance optimizations (#1345)

* State caching

* Better code caching

* Execution optimizaton

* More optimizations

* Updated wasmi

* Caching test

* Style

* Style

* Reverted some minor changes

* Style and typos

* Style and typos

* Removed panics on missing memory

substrate/core/client/src/backend.rs

@@ -68,9 +68,11 @@ pub trait BlockImportOperation<Block, H> where
 	/// has been used to check justification of this block).
 	fn update_authorities(&mut self, authorities: Vec<AuthorityIdFor<Block>>);
 	/// Inject storage data into the database.
-	fn update_storage(&mut self, update: <Self::State as StateBackend<H>>::Transaction) -> error::Result<()>;
+	fn update_db_storage(&mut self, update: <Self::State as StateBackend<H>>::Transaction) -> error::Result<()>;
 	/// Inject storage data into the database replacing any existing data.
 	fn reset_storage(&mut self, top: StorageMap, children: ChildrenStorageMap) -> error::Result<H::Out>;
+	/// Set top level storage changes.
+	fn update_storage(&mut self, update: Vec<(Vec<u8>, Option<Vec<u8>>)>) -> error::Result<()>;
 	/// Inject changes trie data into the database.
 	fn update_changes_trie(&mut self, update: MemoryDB<H>) -> error::Result<()>;
 	/// Update auxiliary keys. Values are `None` if should be deleted.
@@ -127,6 +129,10 @@ pub trait Backend<Block, H>: AuxStore + Send + Sync where
 	fn changes_trie_storage(&self) -> Option<&Self::ChangesTrieStorage>;
 	/// Returns state backend with post-state of given block.
 	fn state_at(&self, block: BlockId<Block>) -> error::Result<Self::State>;
+	/// Destroy state and save any useful data, such as cache.
+	fn destroy_state(&self, _state: Self::State) -> error::Result<()> {
+		Ok(())
+	}
 	/// Attempts to revert the chain by `n` blocks. Returns the number of blocks that were
 	/// successfully reverted.
 	fn revert(&self, n: NumberFor<Block>) -> error::Result<NumberFor<Block>>;