implement Tangerine fork gas cost changes

nimbus/vm/interpreter/gas_costs.nim

@@ -303,7 +303,7 @@ template gasCosts(fork: Fork, prefix, ResultGasCostsName: untyped) =
 
     # Cnew_account
     if gasParams.c_isNewAccount and gasParams.kind == Call:
-      if fork < FkSpurious:
+      when fork < FkSpurious:
         # Pre-EIP161 all account creation calls consumed 25000 gas.
         result.gasCost += static(FeeSchedule[GasNewAccount])
       else:
@@ -321,7 +321,7 @@ template gasCosts(fork: Fork, prefix, ResultGasCostsName: untyped) =
     result.gasCost += static(FeeSchedule[GasCall])
 
     # Cgascap
-    if fork >= FkTangerine:
+    when fork >= FkTangerine:
       # https://github.com/ethereum/EIPs/blob/master/EIPS/eip-150.md
       result.gasRefund =
         if gasParams.c_gasBalance >= result.gasCost:
@@ -578,10 +578,11 @@ func homesteadGasFees(previous_fees: GasFeeSchedule): GasFeeSchedule =
 func tangerineGasFees(previous_fees: GasFeeSchedule): GasFeeSchedule =
   # https://github.com/ethereum/EIPs/blob/master/EIPS/eip-150.md
   result = previous_fees
+  result[GasExtCode]      = 700
   result[GasSload]        = 200
   result[GasSelfDestruct] = 5000
   result[GasBalance]      = 400
-  result[GasCall]         = 40
+  result[GasCall]         = 700
 
 func spuriousGasFees(previous_fees: GasFeeSchedule): GasFeeSchedule =
   # https://github.com/ethereum/EIPs/blob/master/EIPS/eip-160.md

nimbus/vm/interpreter/opcodes_impl.nim

@@ -540,8 +540,13 @@ proc canTransfer(computation: BaseComputation, memPos, memLen: int, value: Uint2
 proc setupCreate(computation: BaseComputation, memPos, len: int, value: Uint256): BaseComputation =
   let
     callData = computation.memory.read(memPos, len)
+
+  var
     createMsgGas = computation.getGasRemaining()
 
+  if getFork(computation) >= FkTangerine:
+    createMsgGas -= createMsgGas div 64
+
   # Consume gas here that will be passed to child
   computation.gasMeter.consumeGas(createMsgGas, reason="CREATE")