[WIP]Implement simple subroutine opcodes

eth/vm/forks/berlin/opcodes.py

@@ -0,0 +1,36 @@
+import copy
+
+from eth_utils.toolz import merge
+
+from eth import constants
+from eth.vm import (
+    mnemonics,
+    opcode_values,
+)
+from eth.vm.opcode import as_opcode
+from eth.vm.forks.istanbul.opcodes import ISTANBUL_OPCODES
+
+
+UPDATED_OPCODES = {
+	opcode_values.BEGINSUB: as_opcode(
+		logic_fn = ...,
+		mnemonic = mnemonics.BEGINSUB,
+		gas_cost = constants.GAS_BASE,
+	),
+	opcode_values.JUMPSUB: as_opcode(
+		logic_fn = ...,
+		mnemonic = mnemonics.JUMPSUB,
+		gas_cost = constants.GAS_MID,
+	),
+	opcode_values.ENDSUB: as_opcode(
+		logic_fn = ...,
+		mnemonic = mnemonics.ENDSUB,
+		gas_cost = constants.GAS_VERYLOW,
+	),
+}
+
+
+BERLIN_OPCODES = merge(
+	copy.deepcopy(ISTANBUL_OPCODES),
+	UPDATED_OPCODES,
+)

eth/vm/mnemonics.py

@@ -162,6 +162,12 @@
 LOG3 = 'LOG3'
 LOG4 = 'LOG4'
 #
+# Subroutines
+#
+BEGINSUB = 'BEGINSUB'
+JUMPSUB = 'JUMPSUB'
+ENDSUB = 'ENDSUB'
+#
 # System
 #
 CREATE = 'CREATE'

eth/vm/opcode_values.py

@@ -182,6 +182,14 @@
 LOG4 = 0xa4
 
 
+#
+# Subroutines
+#
+BEGINSUB = 0xb2
+JUMPSUB = 0xb3
+ENDSUB = 0xb7
+
+
 #
 # System
 #