core, core/vm: added gas price variance table

This implements 1b & 1c of EIP150 by adding a new GasTable which must be
returned from the RuleSet config method. This table is used to determine
the gas prices for the current epoch.

Please note that when the CreateBySuicide gas price is set it is assumed
that we're in the new epoch phase.

In addition this PR will serve as temporary basis while refactorisation
in being done in the EVM64 PR, which will substentially overhaul the gas
price code.

7 files changed, 129 insertions, 20 deletions

diff --git a/core/config.go b/core/config.go
index c0d065a57..3ab04e520 100644
--- a/core/config.go
+++ b/core/config.go
@@ -21,6 +21,7 @@ import (
 	"math/big"
 
 	"github.com/ethereum/go-ethereum/core/vm"
+	"github.com/ethereum/go-ethereum/params"
 )
 
 var ChainConfigNotFoundErr = errors.New("ChainConfig not found") // general config not found error
@@ -35,6 +36,8 @@ type ChainConfig struct {
 	DAOForkBlock   *big.Int `json:"daoForkBlock"`   // TheDAO hard-fork switch block (nil = no fork)
 	DAOForkSupport bool     `json:"daoForkSupport"` // Whether the nodes supports or opposes the DAO hard-fork
 
+	HomesteadGasRepriceBlock *big.Int `json:"homesteadGasRepriceBlock"` // Homestead gas reprice switch block (nil = no fork)
+
 	VmConfig vm.Config `json:"-"`
 }
 
@@ -45,3 +48,14 @@ func (c *ChainConfig) IsHomestead(num *big.Int) bool {
 	}
 	return num.Cmp(c.HomesteadBlock) >= 0
 }
+
+// GasTable returns the gas table corresponding to the current phase (homestead or homestead reprice).
+//
+// The returned GasTable's fields shouldn't, under any circumstances, be changed.
+func (c *ChainConfig) GasTable(num *big.Int) params.GasTable {
+	if c.HomesteadGasRepriceBlock == nil || num == nil || num.Cmp(c.HomesteadGasRepriceBlock) < 0 {
+		return params.GasTableHomestead
+	}
+
+	return params.GasTableHomesteadGasRepriceFork
+}
diff --git a/core/vm/environment.go b/core/vm/environment.go
index a4b2ac196..f8996e648 100644
--- a/core/vm/environment.go
+++ b/core/vm/environment.go
@@ -20,12 +20,16 @@ import (
 	"math/big"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/params"
 )
 
 // RuleSet is an interface that defines the current rule set during the
 // execution of the EVM instructions (e.g. whether it's homestead)
 type RuleSet interface {
 	IsHomestead(*big.Int) bool
+	// GasTable returns the gas prices for this phase, which is based on
+	// block number passed in.
+	GasTable(*big.Int) params.GasTable
 }
 
 // Environment is an EVM requirement and helper which allows access to outside
diff --git a/core/vm/gas.go b/core/vm/gas.go
index eb2c16346..fdbc0df7f 100644
--- a/core/vm/gas.go
+++ b/core/vm/gas.go
@@ -35,8 +35,27 @@ var (
 	GasStop   = big.NewInt(0)
 
 	GasContractByte = big.NewInt(200)
+
+	n64 = big.NewInt(64)
 )
 
+// calcGas returns the actual gas cost of the call.
+//
+// The cost of gas was changed during the homestead price change HF. To allow for EIP150
+// to be implemented. The returned gas is gas - base * 63 / 64.
+func callGas(gasTable params.GasTable, availableGas, base, callCost *big.Int) *big.Int {
+	if gasTable.CreateBySuicide != nil {
+		availableGas = new(big.Int).Sub(availableGas, base)
+		g := new(big.Int).Div(availableGas, n64)
+		g.Sub(availableGas, g)
+
+		if g.Cmp(callCost) < 0 {
+			return g
+		}
+	}
+	return callCost
+}
+
 // baseCheck checks for any stack error underflows
 func baseCheck(op OpCode, stack *Stack, gas *big.Int) error {
 	// PUSH and DUP are a bit special. They all cost the same but we do want to have checking on stack push limit
@@ -127,18 +146,19 @@ var _baseCheck = map[OpCode]req{
 	MSIZE:        {0, GasQuickStep, 1},
 	GAS:          {0, GasQuickStep, 1},
 	BLOCKHASH:    {1, GasExtStep, 1},
-	BALANCE:      {1, GasExtStep, 1},
-	EXTCODESIZE:  {1, GasExtStep, 1},
-	EXTCODECOPY:  {4, GasExtStep, 0},
+	BALANCE:      {1, Zero, 1},
+	EXTCODESIZE:  {1, Zero, 1},
+	EXTCODECOPY:  {4, Zero, 0},
 	SLOAD:        {1, params.SloadGas, 1},
 	SSTORE:       {2, Zero, 0},
 	SHA3:         {2, params.Sha3Gas, 1},
 	CREATE:       {3, params.CreateGas, 1},
-	CALL:         {7, params.CallGas, 1},
-	CALLCODE:     {7, params.CallGas, 1},
-	DELEGATECALL: {6, params.CallGas, 1},
-	JUMPDEST:     {0, params.JumpdestGas, 0},
+	// Zero is calculated in the gasSwitch
+	CALL:         {7, Zero, 1},
+	CALLCODE:     {7, Zero, 1},
+	DELEGATECALL: {6, Zero, 1},
 	SUICIDE:      {1, Zero, 0},
+	JUMPDEST:     {0, params.JumpdestGas, 0},
 	RETURN:       {2, Zero, 0},
 	PUSH1:        {0, GasFastestStep, 1},
 	DUP1:         {0, Zero, 1},
diff --git a/core/vm/instructions.go b/core/vm/instructions.go
index 79aee60d2..3352877c1 100644
--- a/core/vm/instructions.go
+++ b/core/vm/instructions.go
@@ -514,7 +514,12 @@ func opCreate(instr instruction, pc *uint64, env Environment, contract *Contract
 		input        = memory.Get(offset.Int64(), size.Int64())
 		gas          = new(big.Int).Set(contract.Gas)
 	)
-	contract.UseGas(contract.Gas)
+	if env.RuleSet().GasTable(env.BlockNumber()).CreateBySuicide != nil {
+		gas.Div(gas, n64)
+		gas = gas.Sub(contract.Gas, gas)
+	}
+
+	contract.UseGas(gas)
 	_, addr, suberr := env.Create(contract, input, gas, contract.Price, value)
 	// Push item on the stack based on the returned error. If the ruleset is
 	// homestead we must check for CodeStoreOutOfGasError (homestead only
diff --git a/core/vm/runtime/runtime.go b/core/vm/runtime/runtime.go
index 6d980cb32..343aee514 100644
--- a/core/vm/runtime/runtime.go
+++ b/core/vm/runtime/runtime.go
@@ -25,12 +25,16 @@ import (
 	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/ethdb"
+	"github.com/ethereum/go-ethereum/params"
 )
 
 // The default, always homestead, rule set for the vm env
 type ruleSet struct{}
 
 func (ruleSet) IsHomestead(*big.Int) bool { return true }
+func (ruleSet) GasTable(*big.Int) params.GasTable {
+	return params.GasTableHomesteadGasRepriceFork
+}
 
 // Config is a basic type specifying certain configuration flags for running
 // the EVM.
diff --git a/core/vm/util_test.go b/core/vm/util_test.go
index f0d825555..5783ee015 100644
--- a/core/vm/util_test.go
+++ b/core/vm/util_test.go
@@ -16,10 +16,17 @@
 
 package vm
 
-import "math/big"
+import (
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/params"
+)
 
 type ruleSet struct {
 	hs *big.Int
 }
 
 func (r ruleSet) IsHomestead(n *big.Int) bool { return n.Cmp(r.hs) >= 0 }
+func (r ruleSet) GasTable(*big.Int) params.GasTable {
+	return params.GasTableHomestead
+}
diff --git a/core/vm/vm.go b/core/vm/vm.go
index 033ada21c..fcffcf317 100644
--- a/core/vm/vm.go
+++ b/core/vm/vm.go
@@ -44,6 +44,7 @@ type EVM struct {
 	env       Environment
 	jumpTable vmJumpTable
 	cfg       Config
+	gasTable  params.GasTable
 }
 
 // New returns a new instance of the EVM.
@@ -52,6 +53,7 @@ func New(env Environment, cfg Config) *EVM {
 		env:       env,
 		jumpTable: newJumpTable(env.RuleSet(), env.BlockNumber()),
 		cfg:       cfg,
+		gasTable:  env.RuleSet().GasTable(env.BlockNumber()),
 	}
 }
 
@@ -169,7 +171,7 @@ func (evm *EVM) Run(contract *Contract, input []byte) (ret []byte, err error) {
 		// Get the memory location of pc
 		op = contract.GetOp(pc)
 		// calculate the new memory size and gas price for the current executing opcode
-		newMemSize, cost, err = calculateGasAndSize(evm.env, contract, caller, op, statedb, mem, stack)
+		newMemSize, cost, err = calculateGasAndSize(evm.gasTable, evm.env, contract, caller, op, statedb, mem, stack)
 		if err != nil {
 			return nil, err
 		}
@@ -234,7 +236,7 @@ func (evm *EVM) Run(contract *Contract, input []byte) (ret []byte, err error) {
 
 // calculateGasAndSize calculates the required given the opcode and stack items calculates the new memorysize for
 // the operation. This does not reduce gas or resizes the memory.
-func calculateGasAndSize(env Environment, contract *Contract, caller ContractRef, op OpCode, statedb Database, mem *Memory, stack *Stack) (*big.Int, *big.Int, error) {
+func calculateGasAndSize(gasTable params.GasTable, env Environment, contract *Contract, caller ContractRef, op OpCode, statedb Database, mem *Memory, stack *Stack) (*big.Int, *big.Int, error) {
 	var (
 		gas                 = new(big.Int)
 		newMemSize *big.Int = new(big.Int)
@@ -246,6 +248,24 @@ func calculateGasAndSize(env Environment, contract *Contract, caller ContractRef
 
 	// stack Check, memory resize & gas phase
 	switch op {
+	case SUICIDE:
+		// if suicide is not nil: homestead gas fork
+		if gasTable.CreateBySuicide != nil {
+			gas.Set(gasTable.Suicide)
+			if !env.Db().Exist(common.BigToAddress(stack.data[len(stack.data)-1])) {
+				gas.Add(gas, gasTable.CreateBySuicide)
+			}
+		}
+
+		if !statedb.HasSuicided(contract.Address()) {
+			statedb.AddRefund(params.SuicideRefundGas)
+		}
+	case EXTCODESIZE:
+		gas.Set(gasTable.ExtcodeSize)
+	case BALANCE:
+		gas.Set(gasTable.Balance)
+	case SLOAD:
+		gas.Set(gasTable.SLoad)
 	case SWAP1, SWAP2, SWAP3, SWAP4, SWAP5, SWAP6, SWAP7, SWAP8, SWAP9, SWAP10, SWAP11, SWAP12, SWAP13, SWAP14, SWAP15, SWAP16:
 		n := int(op - SWAP1 + 2)
 		err := stack.require(n)
@@ -274,6 +294,8 @@ func calculateGasAndSize(env Environment, contract *Contract, caller ContractRef
 		gas.Add(gas, new(big.Int).Mul(mSize, params.LogDataGas))
 
 		newMemSize = calcMemSize(mStart, mSize)
+
+		quadMemGas(mem, newMemSize, gas)
 	case EXP:
 		gas.Add(gas, new(big.Int).Mul(big.NewInt(int64(len(stack.data[stack.len()-2].Bytes()))), params.ExpByteGas))
 	case SSTORE:
@@ -302,67 +324,100 @@ func calculateGasAndSize(env Environment, contract *Contract, caller ContractRef
 			g = params.SstoreResetGas
 		}
 		gas.Set(g)
-	case SUICIDE:
-		if !statedb.HasSuicided(contract.Address()) {
-			statedb.AddRefund(params.SuicideRefundGas)
-		}
 	case MLOAD:
 		newMemSize = calcMemSize(stack.peek(), u256(32))
+		quadMemGas(mem, newMemSize, gas)
 	case MSTORE8:
 		newMemSize = calcMemSize(stack.peek(), u256(1))
+		quadMemGas(mem, newMemSize, gas)
 	case MSTORE:
 		newMemSize = calcMemSize(stack.peek(), u256(32))
+		quadMemGas(mem, newMemSize, gas)
 	case RETURN:
 		newMemSize = calcMemSize(stack.peek(), stack.data[stack.len()-2])
+		quadMemGas(mem, newMemSize, gas)
 	case SHA3:
 		newMemSize = calcMemSize(stack.peek(), stack.data[stack.len()-2])
 
 		words := toWordSize(stack.data[stack.len()-2])
 		gas.Add(gas, words.Mul(words, params.Sha3WordGas))
+
+		quadMemGas(mem, newMemSize, gas)
 	case CALLDATACOPY:
 		newMemSize = calcMemSize(stack.peek(), stack.data[stack.len()-3])
 
 		words := toWordSize(stack.data[stack.len()-3])
 		gas.Add(gas, words.Mul(words, params.CopyGas))
+
+		quadMemGas(mem, newMemSize, gas)
 	case CODECOPY:
 		newMemSize = calcMemSize(stack.peek(), stack.data[stack.len()-3])
 
 		words := toWordSize(stack.data[stack.len()-3])
 		gas.Add(gas, words.Mul(words, params.CopyGas))
+
+		quadMemGas(mem, newMemSize, gas)
 	case EXTCODECOPY:
+		gas.Set(gasTable.ExtcodeCopy)
+
 		newMemSize = calcMemSize(stack.data[stack.len()-2], stack.data[stack.len()-4])
 
 		words := toWordSize(stack.data[stack.len()-4])
 		gas.Add(gas, words.Mul(words, params.CopyGas))
 
+		quadMemGas(mem, newMemSize, gas)
 	case CREATE:
 		newMemSize = calcMemSize(stack.data[stack.len()-2], stack.data[stack.len()-3])
+
+		quadMemGas(mem, newMemSize, gas)
 	case CALL, CALLCODE:
-		gas.Add(gas, stack.data[stack.len()-1])
+		gas.Set(gasTable.Calls)
 
 		if op == CALL {
 			if !env.Db().Exist(common.BigToAddress(stack.data[stack.len()-2])) {
 				gas.Add(gas, params.CallNewAccountGas)
 			}
 		}
-
 		if len(stack.data[stack.len()-3].Bytes()) > 0 {
 			gas.Add(gas, params.CallValueTransferGas)
 		}
-
 		x := calcMemSize(stack.data[stack.len()-6], stack.data[stack.len()-7])
 		y := calcMemSize(stack.data[stack.len()-4], stack.data[stack.len()-5])
 
 		newMemSize = common.BigMax(x, y)
+
+		quadMemGas(mem, newMemSize, gas)
+
+		cg := callGas(gasTable, contract.Gas, gas, stack.data[stack.len()-1])
+		// Replace the stack item with the new gas calculation. This means that
+		// either the original item is left on the stack or the item is replaced by:
+		// (availableGas - gas) * 63 / 64
+		// We replace the stack item so that it's available when the opCall instruction is
+		// called. This information is otherwise lost due to the dependency on *current*
+		// available gas.
+		stack.data[stack.len()-1] = cg
+		gas.Add(gas, cg)
+
 	case DELEGATECALL:
-		gas.Add(gas, stack.data[stack.len()-1])
+		gas.Set(gasTable.Calls)
 
 		x := calcMemSize(stack.data[stack.len()-5], stack.data[stack.len()-6])
 		y := calcMemSize(stack.data[stack.len()-3], stack.data[stack.len()-4])
 
 		newMemSize = common.BigMax(x, y)
+
+		quadMemGas(mem, newMemSize, gas)
+
+		cg := callGas(gasTable, contract.Gas, gas, stack.data[stack.len()-1])
+		// Replace the stack item with the new gas calculation. This means that
+		// either the original item is left on the stack or the item is replaced by:
+		// (availableGas - gas) * 63 / 64
+		// We replace the stack item so that it's available when the opCall instruction is
+		// called.
+		stack.data[stack.len()-1] = cg
+		gas.Add(gas, cg)
+
 	}
-	quadMemGas(mem, newMemSize, gas)
 
 	return newMemSize, gas, nil
 }