--- a/python/ppci/target/basetarget.py	Sun Mar 02 17:12:08 2014 +0100
+++ b/python/ppci/target/basetarget.py	Fri Mar 07 17:05:32 2014 +0100
@@ -1,49 +1,9 @@
-from ppci.asmnodes import ASymbol, AInstruction, ANumber
 from ppci import CompilerError
 
 """
   Base classes for defining a target
 """
 
-# Machine code interface:
-class Operand:
-   """ Single machine operand """
-   pass
-
-# standard immediates:
-
-class ImmBase:
-    def __init__(self, imm):
-        assert type(imm) is int
-        assert imm < self.Max()
-        self.imm = imm
-
-    @classmethod
-    def Max(cls):
-        return 2**cls.bits
-
-    @classmethod
-    def Create(cls, vop):
-        if type(vop) is ANumber and vop.number < cls.Max():
-            return cls(vop.number)
-
-
-class Imm3(ImmBase):
-    bits = 3
-
-
-class Imm7(ImmBase):
-    bits = 7
-
-
-class Imm8(ImmBase):
-    bits = 8
-
-
-class Imm32(ImmBase):
-    bits = 32
-
-
 class Instruction:
     """ Base instruction class """
     def encode(self):
@@ -76,12 +36,6 @@
     def symbols(self):
         return [self.name]
 
-    @classmethod
-    def Create(cls, vop):
-        if type(vop) is ASymbol:
-            name = vop.name
-            return cls(name)
-
 
 class Comment(PseudoInstruction):
     def __init__(self, txt):
@@ -119,7 +73,7 @@
         return 'DebugInfo: {}'.format(self.info)
 
 
-class Register(Operand):
+class Register:
     def __init__(self, name):
         self.name = name
 
@@ -131,10 +85,16 @@
         self.registers = []
         self.byte_sizes = {'int' : 4}  # For front end!
 
+        # For lowering:
+        self.lower_functions = {}
+
         # For assembler:
         self.assembler_rules = []
         self.asm_keywords = []
 
+        self.generate_base_rules()
+
+    def generate_base_rules(self):
         # Base rules for constants:
         self.add_rule('imm32', ['val32'], lambda x: x[0].val)
         self.add_rule('imm32', ['imm16'], lambda x: x[0])
@@ -162,11 +122,15 @@
     def add_rule(self, lhs, rhs, f):
         self.assembler_rules.append((lhs, rhs, f))
 
-    def instruction(self, cls):
-        """ Decorator function that registers an instruction to this target """
-        self.addInstruction(cls)
-        return cls
+    def lower_frame_to_stream(self, frame, outs):
+        """ Lower instructions from frame to output stream """
+        for im in frame.instructions:
+            if isinstance(im.assem, Instruction):
+                outs.emit(im.assem)
+            else:
+                ins = self.lower_functions[im.assem](im)
+                outs.emit(ins)
 
-    def addInstruction(self, i):
-        pass
-
+    def add_lowering(self, cls, f):
+        """ Add a function to the table of lowering options for this target """
+        self.lower_functions[cls] = f