Add exp support with other bases

mythril/laser/ethereum/instructions.py

@@ -217,9 +217,8 @@ class Instruction:
     @instruction
     def exp_(self, global_state):
         state = global_state.mstate
-        # we only implement 2 ** x
-        base, exponent = util.pop_bitvec(state), util.pop_bitvec(state)
 
+        base, exponent = util.pop_bitvec(state), util.pop_bitvec(state)
         if (type(base) != BitVecNumRef) or (type(exponent) != BitVecNumRef):
             state.stack.append(BitVec("(" + str(simplify(base)) + ")^(" + str(simplify(exponent)) + ")", 256))
         elif base.as_long() == 2:
@@ -228,7 +227,8 @@ class Instruction:
             else:
                 state.stack.append(base << (exponent - 1))
         else:
-            state.stack.append(base)
+            state.stack.append(base.as_long() ** exponent.as_long())
+
         return [global_state]
 
     @instruction