ir: add IRNop and IRVoid action and value (resp.)

compiler/ir.py

@@ -31,6 +31,17 @@ class IRAction(IRItem, abc.ABC):
     pass
 
 
+class IRNop(IRAction):
+    def __init__(self, location: SourceLocation):
+        super().__init__(location)
+
+    def codegen(self) -> str:
+        return "NOP"
+
+    def destination(self) -> IRValue:
+        return IRVoid(self.location)
+
+
 class IRValue(IRItem, abc.ABC):
     def destination(self) -> IRValue:
         return self
@@ -61,6 +72,15 @@ class IRImmediate(IRValue):
         return f"{self.value}"
 
 
+class IRVoid(IRValue):
+    @typecheck
+    def __init__(self, location: SourceLocation):
+        super().__init__(location)
+
+    def codegen(self) -> str:
+        return "<VOID>"
+
+
 class IRAssignable(IRValue, metaclass=abc.ABCMeta):
     pass