Add incomplete LLVM pretty printing.

ll.py

@@ -54,3 +54,34 @@ Null = namedtuple('Null', [])
 Const = namedtuple('Const', ['val'])
 Gid = namedtuple('Gid', ['val'])
 Id = namedtuple('Id', ['val'])
+
+
+def ty2s(ty):
+    if ty == SimpleType.I64:
+        return 'i64'
+    else:
+        # TODO
+        print('Unknown type: {}'
+              .format(ty))
+
+
+def oper2s(operand):
+    if isinstance(operand, Const):
+        return str(operand.val)
+    elif isinstance(operand, Id):
+        return '%' + operand.val
+    else:
+        # TODO
+        print('Unknown operand: {}'
+              .format(operand))
+
+
+def insn2s(insn):
+    if isinstance(insn, Binop):
+        return ('{} {} {}, {}'
+                .format(insn.bop, ty2s(insn.ty),
+                        oper2s(insn.left), oper2s(insn.right)))
+    else:
+        # TODO
+        print('Unknown insn: {}'
+              .format(insn))