core, params: polish net gas metering PR a bit

5 files changed, 55 insertions, 149 deletions

diff --git a/core/vm/gas_table.go b/core/vm/gas_table.go
index 77250978d..10b4f719a 100644
--- a/core/vm/gas_table.go
+++ b/core/vm/gas_table.go
@@ -117,78 +117,69 @@ func gasReturnDataCopy(gt params.GasTable, evm *EVM, contract *Contract, stack *
 
 func gasSStore(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
 	var (
-		y, x = stack.Back(1), stack.Back(0)
-		val  = evm.StateDB.GetState(contract.Address(), common.BigToHash(x))
-	)
-	// This checks for 3 scenario's and calculates gas accordingly
-	// 1. From a zero-value address to a non-zero value         (NEW VALUE)
-	// 2. From a non-zero value address to a zero-value address (DELETE)
-	// 3. From a non-zero to a non-zero                         (CHANGE)
-	if val == (common.Hash{}) && y.Sign() != 0 {
-		// 0 => non 0
-		return params.SstoreSetGas, nil
-	} else if val != (common.Hash{}) && y.Sign() == 0 {
-		// non 0 => 0
-		evm.StateDB.AddRefund(params.SstoreRefundGas)
-		return params.SstoreClearGas, nil
-	} else {
-		// non 0 => non 0 (or 0 => 0)
-		return params.SstoreResetGas, nil
-	}
-}
-
-// gasSStoreEip1283 calculates SSTORE gas cost according to EIP-1283
-func gasSStoreEip1283(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
-	var (
 		y, x    = stack.Back(1), stack.Back(0)
 		current = evm.StateDB.GetState(contract.Address(), common.BigToHash(x))
 	)
-	//1. If current value equals new value (this is a no-op), 200 gas is deducted.
-	//2. If current value does not equal new value
-	//  2.1 If original value equals current value (this storage slot has not been changed by the current execution context)
-	//    2.1.1 If original value is 0, 20000 gas is deducted.
-	//	  2.1.2 Otherwise, 5000 gas is deducted. If new value is 0, add 15000 gas to refund counter.
-	//	2.2 If original value does not equal current value (this storage slot is dirty), 200 gas is deducted. Apply both of the following clauses.
-	//	  2.2.1 If original value is not 0
-	//      2.2.1.1 If current value is 0 (also means that new value is not 0), remove 15000 gas from refund counter. We can prove that refund counter will never go below 0.
-	//      2.2.1.2 If new value is 0 (also means that current value is not 0), add 15000 gas to refund counter.
-	//	  2.2.2 If original value equals new value (this storage slot is reset)
-	//      2.2.2.1 If original value is 0, add 19800 gas to refund counter.
-	//	    2.2.2.2 Otherwise, add 4800 gas to refund counter.
-	new := common.BigToHash(y)
-	if current == new {
-		// 1. current == new
-		return 200, nil
-	}
-	original := evm.StateDB.GetStateOriginal(contract.Address(), common.BigToHash(x))
-	// 2
-	if original == current { // 2.1
-		if original == (common.Hash{}) { // 2.1.1
-			return 20000, nil
+	// The legacy gas metering only takes into consideration the current state
+	if !evm.chainRules.IsConstantinople {
+		// This checks for 3 scenario's and calculates gas accordingly:
+		//
+		// 1. From a zero-value address to a non-zero value         (NEW VALUE)
+		// 2. From a non-zero value address to a zero-value address (DELETE)
+		// 3. From a non-zero to a non-zero                         (CHANGE)
+		switch {
+		case current == (common.Hash{}) && y.Sign() != 0: // 0 => non 0
+			return params.SstoreSetGas, nil
+		case current != (common.Hash{}) && y.Sign() == 0: // non 0 => 0
+			evm.StateDB.AddRefund(params.SstoreRefundGas)
+			return params.SstoreClearGas, nil
+		default: // non 0 => non 0 (or 0 => 0)
+			return params.SstoreResetGas, nil
+		}
+	}
+	// The new gas metering is based on net gas costs (EIP-1283):
+	//
+	// 1. If current value equals new value (this is a no-op), 200 gas is deducted.
+	// 2. If current value does not equal new value
+	//   2.1. If original value equals current value (this storage slot has not been changed by the current execution context)
+	//     2.1.1. If original value is 0, 20000 gas is deducted.
+	// 	   2.1.2. Otherwise, 5000 gas is deducted. If new value is 0, add 15000 gas to refund counter.
+	// 	2.2. If original value does not equal current value (this storage slot is dirty), 200 gas is deducted. Apply both of the following clauses.
+	// 	  2.2.1. If original value is not 0
+	//       2.2.1.1. If current value is 0 (also means that new value is not 0), remove 15000 gas from refund counter. We can prove that refund counter will never go below 0.
+	//       2.2.1.2. If new value is 0 (also means that current value is not 0), add 15000 gas to refund counter.
+	// 	  2.2.2. If original value equals new value (this storage slot is reset)
+	//       2.2.2.1. If original value is 0, add 19800 gas to refund counter.
+	// 	     2.2.2.2. Otherwise, add 4800 gas to refund counter.
+	value := common.BigToHash(y)
+	if current == value { // noop (1)
+		return params.NetSstoreNoopGas, nil
+	}
+	original := evm.StateDB.GetCommittedState(contract.Address(), common.BigToHash(x))
+	if original == current {
+		if original == (common.Hash{}) { // create slot (2.1.1)
+			return params.NetSstoreInitGas, nil
 		}
-		// 2.1.2
-		if new == (common.Hash{}) {
-			evm.StateDB.AddRefund(15000)
+		if value == (common.Hash{}) { // delete slot (2.1.2b)
+			evm.StateDB.AddRefund(params.NetSstoreClearRefund)
 		}
-		return 5000, nil
-	}
-	// 2.2
-	if original != (common.Hash{}) { // 2.2.1
-		if current == (common.Hash{}) { // 2.2.1.1
-			evm.StateDB.SubRefund(15000)
-		} else {
-			// 2.2.1.2
-			evm.StateDB.AddRefund(15000)
+		return params.NetSstoreCleanGas, nil // write existing slot (2.1.2)
+	}
+	if original != (common.Hash{}) {
+		if current == (common.Hash{}) { // recreate slot (2.2.1.1)
+			evm.StateDB.SubRefund(params.NetSstoreClearRefund)
+		} else if value == (common.Hash{}) { // delete slot (2.2.1.2)
+			evm.StateDB.AddRefund(params.NetSstoreClearRefund)
 		}
 	}
-	if original == new { // 2.2.2
-		if original == (common.Hash{}) {
-			evm.StateDB.AddRefund(19800)
-		} else {
-			evm.StateDB.AddRefund(4800)
+	if original == value {
+		if original == (common.Hash{}) { // reset to original inexistent slot (2.2.2.1)
+			evm.StateDB.AddRefund(params.NetSstoreResetClearRefund)
+		} else { // reset to original existing slot (2.2.2.2)
+			evm.StateDB.AddRefund(params.NetSstoreResetRefund)
 		}
 	}
-	return 200, nil
+	return params.NetSstoreDirtyGas, nil
 }
 
 func makeGasLog(n uint64) gasFunc {
diff --git a/core/vm/interface.go b/core/vm/interface.go
index 2e2e3e925..fc15082f1 100644
--- a/core/vm/interface.go
+++ b/core/vm/interface.go
@@ -43,8 +43,8 @@ type StateDB interface {
 	SubRefund(uint64)
 	GetRefund() uint64
 
+	GetCommittedState(common.Address, common.Hash) common.Hash
 	GetState(common.Address, common.Hash) common.Hash
-	GetStateOriginal(common.Address, common.Hash) common.Hash
 	SetState(common.Address, common.Hash, common.Hash)
 
 	Suicide(common.Address) bool
diff --git a/core/vm/jump_table.go b/core/vm/jump_table.go
index 8a997adc4..deedf70cd 100644
--- a/core/vm/jump_table.go
+++ b/core/vm/jump_table.go
@@ -95,14 +95,6 @@ func newConstantinopleInstructionSet() [256]operation {
 		writes:        true,
 		returns:       true,
 	}
-	instructionSet[SSTORE] = operation{
-		execute:       opSstore,
-		gasCost:       gasSStoreEip1283,
-		validateStack: makeStackFunc(2, 0),
-		valid:         true,
-		writes:        true,
-	}
-
 	return instructionSet
 }
 
diff --git a/core/vm/logger_test.go b/core/vm/logger_test.go
index 28830c445..cdbb70dc4 100644
--- a/core/vm/logger_test.go
+++ b/core/vm/logger_test.go
@@ -41,11 +41,6 @@ func (d *dummyContractRef) SetBalance(*big.Int)        {}
 func (d *dummyContractRef) SetNonce(uint64)            {}
 func (d *dummyContractRef) Balance() *big.Int          { return new(big.Int) }
 
-type dummyStateDB struct {
-	NoopStateDB
-	ref *dummyContractRef
-}
-
 func TestStoreCapture(t *testing.T) {
 	var (
 		env      = NewEVM(Context{}, nil, params.TestChainConfig, Config{})
diff --git a/core/vm/noop.go b/core/vm/noop.go
deleted file mode 100644
index 19539d978..000000000
--- a/core/vm/noop.go
+++ /dev/null
@@ -1,72 +0,0 @@
-// Copyright 2016 The go-ethereum Authors
-// This file is part of the go-ethereum library.
-//
-// The go-ethereum library is free software: you can redistribute it and/or modify
-// it under the terms of the GNU Lesser General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// The go-ethereum library is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU Lesser General Public License for more details.
-//
-// You should have received a copy of the GNU Lesser General Public License
-// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
-
-package vm
-
-import (
-	"math/big"
-
-	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/core/types"
-)
-
-func NoopCanTransfer(db StateDB, from common.Address, balance *big.Int) bool {
-	return true
-}
-func NoopTransfer(db StateDB, from, to common.Address, amount *big.Int) {}
-
-type NoopEVMCallContext struct{}
-
-func (NoopEVMCallContext) Call(caller ContractRef, addr common.Address, data []byte, gas, value *big.Int) ([]byte, error) {
-	return nil, nil
-}
-func (NoopEVMCallContext) CallCode(caller ContractRef, addr common.Address, data []byte, gas, value *big.Int) ([]byte, error) {
-	return nil, nil
-}
-func (NoopEVMCallContext) Create(caller ContractRef, data []byte, gas, value *big.Int) ([]byte, common.Address, error) {
-	return nil, common.Address{}, nil
-}
-func (NoopEVMCallContext) DelegateCall(me ContractRef, addr common.Address, data []byte, gas *big.Int) ([]byte, error) {
-	return nil, nil
-}
-
-type NoopStateDB struct{}
-
-func (NoopStateDB) CreateAccount(common.Address)                                       {}
-func (NoopStateDB) SubBalance(common.Address, *big.Int)                                {}
-func (NoopStateDB) AddBalance(common.Address, *big.Int)                                {}
-func (NoopStateDB) GetBalance(common.Address) *big.Int                                 { return nil }
-func (NoopStateDB) GetNonce(common.Address) uint64                                     { return 0 }
-func (NoopStateDB) SetNonce(common.Address, uint64)                                    {}
-func (NoopStateDB) GetCodeHash(common.Address) common.Hash                             { return common.Hash{} }
-func (NoopStateDB) GetCode(common.Address) []byte                                      { return nil }
-func (NoopStateDB) SetCode(common.Address, []byte)                                     {}
-func (NoopStateDB) GetCodeSize(common.Address) int                                     { return 0 }
-func (NoopStateDB) AddRefund(uint64)                                                   {}
-func (NoopStateDB) SubRefund(uint64)                                                   {}
-func (NoopStateDB) GetRefund() uint64                                                  { return 0 }
-func (NoopStateDB) GetState(common.Address, common.Hash) common.Hash                   { return common.Hash{} }
-func (NoopStateDB) GetStateOriginal(common.Address, common.Hash) common.Hash           { return common.Hash{} }
-func (NoopStateDB) SetState(common.Address, common.Hash, common.Hash)                  {}
-func (NoopStateDB) Suicide(common.Address) bool                                        { return false }
-func (NoopStateDB) HasSuicided(common.Address) bool                                    { return false }
-func (NoopStateDB) Exist(common.Address) bool                                          { return false }
-func (NoopStateDB) Empty(common.Address) bool                                          { return false }
-func (NoopStateDB) RevertToSnapshot(int)                                               {}
-func (NoopStateDB) Snapshot() int                                                      { return 0 }
-func (NoopStateDB) AddLog(*types.Log)                                                  {}
-func (NoopStateDB) AddPreimage(common.Hash, []byte)                                    {}
-func (NoopStateDB) ForEachStorage(common.Address, func(common.Hash, common.Hash) bool) {}