Problem: no efficient GetStorageRoot impl in cosmos/evm (#9)

Solution:
- create a new method IsStorageEmpty to use in core evm

Author: yihuang

core/state/statedb.go

@@ -335,6 +335,12 @@ func (s *StateDB) GetStorageRoot(addr common.Address) common.Hash {
 	return common.Hash{}
 }
 
+// IsStorageEmpty returns if the contract storage is empty
+func (s *StateDB) IsStorageEmpty(addr common.Address) bool {
+	storageRoot := s.GetStorageRoot(addr)
+	return storageRoot == (common.Hash{}) || storageRoot == types.EmptyRootHash
+}
+
 // TxIndex returns the current transaction index set by SetTxContext.
 func (s *StateDB) TxIndex() int {
 	return s.txIndex

core/state/statedb_hooked.go

@@ -97,6 +97,10 @@ func (s *hookedStateDB) GetStorageRoot(addr common.Address) common.Hash {
 	return s.inner.GetStorageRoot(addr)
 }
 
+func (s *hookedStateDB) IsStorageEmpty(addr common.Address) bool {
+	return s.inner.IsStorageEmpty(addr)
+}
+
 func (s *hookedStateDB) GetTransientState(addr common.Address, key common.Hash) common.Hash {
 	return s.inner.GetTransientState(addr, key)
 }

core/vm/evm.go

@@ -499,10 +499,10 @@ func (evm *EVM) create(caller common.Address, code []byte, gas uint64, value *ui
 	// - the code is non-empty
 	// - the storage is non-empty
 	contractHash := evm.StateDB.GetCodeHash(address)
-	storageRoot := evm.StateDB.GetStorageRoot(address)
+	isStorageEmpty := evm.StateDB.IsStorageEmpty(address)
 	if evm.StateDB.GetNonce(address) != 0 ||
 		(contractHash != (common.Hash{}) && contractHash != types.EmptyCodeHash) || // non-empty code
-		(storageRoot != (common.Hash{}) && storageRoot != types.EmptyRootHash) { // non-empty storage
+		!isStorageEmpty { // non-empty storage
 		if evm.Config.Tracer != nil && evm.Config.Tracer.OnGasChange != nil {
 			evm.Config.Tracer.OnGasChange(gas, 0, tracing.GasChangeCallFailedExecution)
 		}

core/vm/interface.go

@@ -54,6 +54,7 @@ type StateDB interface {
 	GetState(common.Address, common.Hash) common.Hash
 	SetState(common.Address, common.Hash, common.Hash) common.Hash
 	GetStorageRoot(addr common.Address) common.Hash
+	IsStorageEmpty(addr common.Address) bool
 
 	GetTransientState(addr common.Address, key common.Hash) common.Hash
 	SetTransientState(addr common.Address, key, value common.Hash)