interpreter dispatch simplification

nimbus/vm/interpreter_dispatch.nim

@@ -17,7 +17,7 @@ logScope:
   topics = "vm opcode"
 
 func invalidInstruction*(computation: var BaseComputation) {.inline.} =
-  raise newException(ValueError, "Invalid instruction, received an opcode not implemented in the current fork.")
+  raise newException(InvalidInstruction, "Invalid instruction, received an opcode not implemented in the current fork.")
 
 let FrontierOpDispatch {.compileTime.}: array[Op, NimNode] = block:
   fill_enum_table_holes(Op, newIdentNode("invalidInstruction")):
@@ -256,24 +256,20 @@ proc homesteadVM(computation: var BaseComputation) =
   if not computation.execPrecompiles:
     genHomesteadDispatch(computation)
 
-proc updateOpcodeExec*(computation: var BaseComputation, fork: Fork) =
-  case fork
-  of FkFrontier..FkThawing:
-    computation.opCodeExec = frontierVM
-    computation.frontierVM()
-  of FkHomestead..FkSpurious:
-    computation.opCodeExec = homesteadVM
-    computation.homesteadVM()
-  else:
-    raise newException(VMError, "Unknown or not implemented fork: " & $fork)
-
 proc executeOpcodes*(computation: var BaseComputation) =
   # TODO: Optimise getting fork and updating opCodeExec only when necessary
   let fork = computation.getFork
+
   try:
-    computation.updateOpcodeExec(fork)
+    case fork
+    of FkFrontier..FkThawing:
+      computation.opCodeExec = frontierVM
+      computation.frontierVM()
+    of FkHomestead..FkSpurious:
+      computation.opCodeExec = homesteadVM
+      computation.homesteadVM()
+    else:
+      raise newException(VMError, "Unknown or not implemented fork: " & $fork)
   except VMError:
     computation.error = Error(info: getCurrentExceptionMsg())
     debug "VM Error executeOpcodes() failed", error = getCurrentExceptionMsg()
-  except EVMError:
-    debug "EVM Error executeOpcodes() failed", error = getCurrentExceptionMsg()