implement EIP-2200 stub

nimbus/vm/interpreter/gas_costs.nim

@@ -208,20 +208,45 @@ template gasCosts(fork: Fork, prefix, ResultGasCostsName: untyped) =
   func `prefix gasSstore`(value: Uint256, gasParams: Gasparams): GasResult {.nimcall.} =
     ## Value is word to save
 
-    # workaround for static evaluation not working for if expression
-    const
-      gSet = FeeSchedule[GasSset]
-      gSreset = FeeSchedule[GasSreset]
+    when fork < FkIstanbul:
+      # workaround for static evaluation not working for if expression
+      const
+        gSet = FeeSchedule[GasSset]
+        gSreset = FeeSchedule[GasSreset]
 
-    # Gas cost - literal translation of Yellow Paper
-    result.gasCost = if value.isZero.not and gasParams.s_isStorageEmpty:
-                       gSet
-                     else:
-                       gSreset
+      # Gas cost - literal translation of Yellow Paper
+      result.gasCost = if value.isZero.not and gasParams.s_isStorageEmpty:
+                        gSet
+                      else:
+                        gSreset
 
-    # Refund
-    if value.isZero and not gasParams.s_isStorageEmpty:
-      result.gasRefund = static(FeeSchedule[RefundSclear])
+      # Refund
+      if value.isZero and not gasParams.s_isStorageEmpty:
+        result.gasRefund = static(FeeSchedule[RefundSclear])
+    else:
+      # 0. If *gasleft* is less than or equal to 2300, fail the current call.
+      # 1. If current value equals new value (this is a no-op), SSTORE_NOOP_GAS 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, SSTORE_INIT_GAS gas is deducted.
+      #     2.1.2. Otherwise, SSTORE_CLEAN_GAS gas is deducted. If new value is 0, add SSTORE_CLEAR_REFUND to refund counter.
+      #   2.2. If original value does not equal current value (this storage slot is dirty), SSTORE_DIRTY_GAS 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), subtract SSTORE_CLEAR_REFUND 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 SSTORE_CLEAR_REFUND 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 SSTORE_INIT_REFUND to refund counter.
+      #       2.2.2.2. Otherwise, add SSTORE_CLEAN_REFUND gas to refund counter.
+      const
+        NoopGasEIP2200     = FeeSchedule[GasSload] # if the value doesn't change.
+        DirtyGasEIP2200    = FeeSchedule[GasSload] # if a dirty value is changed.
+        InitGasEIP2200     = FeeSchedule[GasSset]  # from clean zero to non-zero
+        InitRefundEIP2200  = FeeSchedule[GasSset] - FeeSchedule[GasSload] # resetting to the original zero value
+        CleanGasEIP2200    = FeeSchedule[GasSreset]# from clean non-zero to something else
+        CleanRefundEIP2200 = FeeSchedule[GasSreset] - FeeSchedule[GasSload] # resetting to the original non-zero value
+        ClearRefundEIP2200 = FeeSchedule[RefundSclear]# clearing an originally existing storage slot
+
+      # Gas sentry honoured, do the actual gas calculation based on the stored value
 
   func `prefix gasLog0`(currentMemSize, memOffset, memLength: GasNatural): GasInt {.nimcall.} =
     result = `prefix gasMemoryExpansion`(currentMemSize, memOffset, memLength)
@@ -611,6 +636,7 @@ func istanbulGasFees(previous_fees: GasFeeSchedule): GasFeeSchedule =
   result[GasExtCodeHash]  = 700
   result[GasBalance]      = 700
   result[GasTXDataNonZero]= 16
+
 const
   HomesteadGasFees = BaseGasFees.homesteadGasFees
   TangerineGasFees = HomesteadGasFees.tangerineGasFees

nimbus/vm/interpreter/opcodes_impl.nim

@@ -930,3 +930,7 @@ op extCodeHash, inline = true:
     push: 0
   else:
     push: computation.vmState.readOnlyStateDB.getCodeHash(address)
+
+op sstoreEIP2200, inline = false, slot, value:
+  checkInStaticContext(computation)
+  # TODO: stub

nimbus/vm/interpreter_dispatch.nim

@@ -219,6 +219,7 @@ proc genIstanbulJumpTable(ops: array[Op, NimNode]): array[Op, NimNode] {.compile
   result = ops
   result[ChainId] = newIdentNode "chainId"
   result[SelfBalance] = newIdentNode "selfBalance"
+  result[SStore] = newIdentNode "sstoreEIP2200"
 
 let IstanbulOpDispatch {.compileTime.}: array[Op, NimNode] = genIstanbulJumpTable(ConstantinopleOpDispatch)