EIP-4399 implementation of nim-vm2

new addition:
  - `RANDOM` opcode
  - `random` field of BlockHeader(previously `mixDigest`)
  - `PostMerge` temporary name of this new EVM version

nimbus/vm2/computation.nim

@@ -58,6 +58,9 @@ template getBlockNumber*(c: Computation): Uint256 =
 template getDifficulty*(c: Computation): DifficultyInt =
   c.vmState.difficulty
 
+template getRandom*(c: Computation): Hash256 =
+  c.vmState.random
+
 template getGasLimit*(c: Computation): GasInt =
   c.vmState.gasLimit
 

nimbus/vm2/interpreter/gas_costs.nim

@@ -730,7 +730,8 @@ const
     FkPetersburg: SpuriousGasFees,
     FkIstanbul: IstanbulGasFees,
     FkBerlin: BerlinGasFees,
-    FkLondon: LondonGasFees
+    FkLondon: LondonGasFees,
+    FkPostMerge: LondonGasFees
   ]
 
 
@@ -742,6 +743,7 @@ gasCosts(FkConstantinople, constantinople, ConstantinopleGasCosts)
 gasCosts(FkIstanbul, istanbul, IstanbulGasCosts)
 gasCosts(FkBerlin, berlin, BerlinGasCosts)
 gasCosts(FkLondon, london, LondonGasCosts)
+gasCosts(FkPostMerge, postMerge, PostMergeGasCosts)
 
 proc forkToSchedule*(fork: Fork): GasCosts =
   if fork < FkHomestead:
@@ -758,8 +760,10 @@ proc forkToSchedule*(fork: Fork): GasCosts =
     IstanbulGasCosts
   elif fork < FkLondon:
     BerlinGasCosts
-  else:
+  elif fork < FkPostMerge:
     LondonGasCosts
+  else:
+    PostMergeGasCosts
 
 const
   ## Precompile costs

nimbus/vm2/interpreter/op_codes.nim

@@ -209,6 +209,10 @@ type
     SelfDestruct =   0xff  ## Halt execution and register account for later
                            ## deletion.
 
+const
+  # EIP-4399 new opcode
+  Random* = Difficulty
+  
 # ------------------------------------------------------------------------------
 # Verify that Op is contiguous and sym names follow some standards
 # ------------------------------------------------------------------------------

nimbus/vm2/interpreter/op_handlers/oph_blockdata.nim

@@ -53,6 +53,11 @@ const
     k.cpt.stack.push:
       k.cpt.getDifficulty
 
+  randomOp: Vm2OpFn = proc (k: var Vm2Ctx) =
+    ## 0x44, Get the block's randomness
+    k.cpt.stack.push:
+      k.cpt.getRandom
+
   gasLimitOp: Vm2OpFn = proc (k: var Vm2Ctx) =
     ## 0x45, Get the block's gas limit
     k.cpt.stack.push:
@@ -113,7 +118,7 @@ const
             post: vm2OpIgnore)),
 
     (opCode: Difficulty,      ## 0x44, Block difficulty
-     forks: Vm2OpAllForks,
+     forks: Vm2OpAllForks - Vm2OpPostMergeAndLater,
      name: "difficulty",
      info: "Get the block's difficulty",
      exec: (prep: vm2OpIgnore,
@@ -150,6 +155,14 @@ const
      info: "Get current block's EIP-1559 base fee",
      exec: (prep: vm2OpIgnore,
             run:  baseFeeOp,
+            post: vm2OpIgnore)),
+
+    (opCode: Random,          ## 0x44, EIP-4399 Block randomness.
+     forks: Vm2OpPostMergeAndLater,
+     name: "random",
+     info: "Get current block's EIP-4399 randomness",
+     exec: (prep: vm2OpIgnore,
+            run:  randomOp,
             post: vm2OpIgnore))]
 
 # ------------------------------------------------------------------------------

nimbus/vm2/interpreter/op_handlers/oph_defs.nim

@@ -81,6 +81,9 @@ const
   Vm2OpLondonAndLater* =
     Vm2OpBerlinAndLater - {FkBerlin}
 
+  Vm2OpPostMergeAndLater* =
+    Vm2OpLondonAndLater - {FkLondon}
+
 # ------------------------------------------------------------------------------
 # End
 # ------------------------------------------------------------------------------

nimbus/vm2/state.nim

@@ -58,6 +58,7 @@ proc init(
       timestamp:   EthTime;
       gasLimit:    GasInt;
       fee:         Option[Uint256];
+      random:      Hash256;
       miner:       EthAddress;
       chainDB:     BaseChainDB;
       tracer:      TransactionTracer)
@@ -69,6 +70,7 @@ proc init(
   self.timestamp = timestamp
   self.gasLimit = gasLimit
   self.fee = fee
+  self.random = random
   self.chaindb = chainDB
   self.tracer = tracer
   self.logEntries = @[]
@@ -83,6 +85,7 @@ proc init(
       timestamp:   EthTime;
       gasLimit:    GasInt;
       fee:         Option[Uint256];
+      random:      Hash256;
       miner:       EthAddress;
       chainDB:     BaseChainDB;
       tracerFlags: set[TracerFlags])
@@ -95,6 +98,7 @@ proc init(
     timestamp = timestamp,
     gasLimit  = gasLimit,
     fee       = fee,
+    random    = random,
     miner     = miner,
     chainDB   = chainDB,
     tracer    = tracer)
@@ -116,6 +120,7 @@ proc new*(
       timestamp:   EthTime;         ## tx env: time stamp
       gasLimit:    GasInt;          ## tx env: gas limit
       fee:         Option[Uint256]; ## tx env: optional base fee
+      random:      Hash256;         ## tx env: POS block randomness
       miner:       EthAddress;      ## tx env: coinbase(PoW) or signer(PoA)
       chainDB:     BaseChainDB;     ## block chain database
       tracerFlags: set[TracerFlags] = {};
@@ -135,6 +140,7 @@ proc new*(
     timestamp   = timestamp,
     gasLimit    = gasLimit,
     fee         = fee,
+    random      = random,
     miner       = miner,
     chainDB     = chainDB,
     tracerFlags = tracerFlags)
@@ -144,6 +150,7 @@ proc reinit*(self:      BaseVMState;     ## Object descriptor
              timestamp: EthTime;         ## tx env: time stamp
              gasLimit:  GasInt;          ## tx env: gas limit
              fee:       Option[Uint256]; ## tx env: optional base fee
+             random:    Hash256;         ## tx env: POS block randomness
              miner:     EthAddress;      ## tx env: coinbase(PoW) or signer(PoA)
              pruneTrie: bool = true): bool
     {.gcsafe, raises: [Defect,CatchableError].} =
@@ -168,6 +175,7 @@ proc reinit*(self:      BaseVMState;     ## Object descriptor
       timestamp   = timestamp,
       gasLimit    = gasLimit,
       fee         = fee,
+      random      = random,
       miner       = miner,
       chainDB     = db,
       tracer      = tracer)
@@ -190,6 +198,7 @@ proc reinit*(self:      BaseVMState; ## Object descriptor
     timestamp = header.timestamp,
     gasLimit  = header.gasLimit,
     fee       = header.fee,
+    random    = header.random,
     miner     = self.chainDB.getMinerAddress(header),
     pruneTrie = pruneTrie)
 
@@ -226,6 +235,7 @@ proc init*(
             header.timestamp,
             header.gasLimit,
             header.fee,
+            header.random,
             chainDB.getMinerAddress(header),
             chainDB,
             tracerFlags)

nimbus/vm2/types.nim

@@ -29,6 +29,7 @@ type
     timestamp*     : EthTime
     gasLimit*      : GasInt
     fee*           : Option[Uint256]
+    random*        : Hash256
     name*          : string
     flags*         : set[VMFlag]
     tracer*        : TransactionTracer