Add bitcast.

ll.py

@@ -102,6 +102,10 @@ def insn2s(insn):
         return ('icmp {} {} {}, {}'
                 .format(insn.cnd, ty2s(insn.ty),
                         oper2s(insn.left), oper2s(insn.right)))
+    elif isinstance(insn, Bitcast):
+        return ('bitcast {} {} to {}'
+                .format(ty2s(insn.from_ty), oper2s(insn.oper),
+                        ty2s(insn.to_ty)))
     elif isinstance(insn, Zext):
         return ('zext {} {} to {}'
                 .format(ty2s(insn.from_ty), oper2s(insn.oper),

stepper.py

@@ -51,6 +51,16 @@ def step(insns, terminator, blocks, stack_frames, ssa_env, global_env, memory,
         # TODO
         print('icmp {} {}, {}'
               .format(cnd,  left_v, right_v))
+    elif isinstance(next_insn, ll.Bitcast):
+        oper = next_insn.oper
+        from_ty = next_insn.from_ty
+        to_ty = next_insn.to_ty
+        oper_v = eval_oper(oper, ssa_env, global_env)
+        res = oper_v
+
+        # TODO
+        print('bitcast {} {} to {}'
+              .format(ll.ty2s(from_ty), oper_v, ll.ty2s(to_ty)))
     elif isinstance(next_insn, ll.Zext):
         oper = next_insn.oper
         from_ty = next_insn.from_ty