--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/python/codegen/registerallocator.py	Sun Dec 01 13:36:58 2013 +0100
@@ -0,0 +1,200 @@
+from .flowgraph import FlowGraph
+from .interferencegraph import InterferenceGraph
+
+# Nifty first function:
+first = lambda x: next(iter(x))
+
+class RegisterAllocator:
+    """
+        Target independent register allocator.
+
+        Algorithm is iterated register coalescing by Appel and George.
+
+        Chaitin's algorithm: remove all nodes with less than K neighbours.
+        These nodes can be colored when added back.
+
+        The process consists of the following steps:
+        - build interference graph from the instruction list
+        - remove low degree non move related nodes.
+        - (optional) coalesc registers to remove redundant moves
+        - (optional) spill registers
+        - select registers
+    """
+
+    def InitData(self, f):
+        self.f = f
+        # Register information:
+        self.regs = set(f.regs)
+        self.K = len(self.regs)
+
+        # Move related sets:
+        self.coalescedMoves = set()
+        self.constrainedMoves = set()
+        self.frozenMoves = set()
+        self.activeMoves = set()
+        self.worklistMoves = set()
+
+    def printLive(self):
+        print('Liveness:')
+        for i in self.f.instructions:
+            cfgn = self.f.cfg._map[i]
+            print(i, cfgn.live_in)
+
+    def Build(self):
+        """ 1. Construct interference graph from instruction list """
+        self.f.cfg = FlowGraph(self.f.instructions)
+        self.f.ig = InterferenceGraph(self.f.cfg)
+
+        self.Node = self.f.ig.getNode
+
+        # Divide nodes into pre-colored and initial:
+        pre_tmp = list(self.f.tempMap.keys())
+        self.precolored = set(self.Node(tmp) for tmp in pre_tmp)
+        self.workSet = set(self.f.ig.nodes - self.precolored)
+
+        for n in self.precolored:
+            n.addDegree = 100 + len(self.f.ig.nodes) + self.K
+
+        # Initialize color map:
+        self.color = {}
+        for tmp, c in self.f.tempMap.items():
+            self.color[self.Node(tmp)] = c
+
+        self.moves = [i for i in self.f.instructions if i.ismove]
+        for mv in self.moves:
+            self.Node(mv.src[0]).moves.add(mv)
+            self.Node(mv.dst[0]).moves.add(mv)
+
+    def NodeMoves(self, n):
+        return n.moves & (self.activeMoves | self.worklistMoves)
+    
+    def MoveRelated(self, n):
+        return bool(self.NodeMoves(n))
+
+    @property
+    def SpillWorkSet(self):
+        c = lambda n: n.Degree >= self.K
+        return set(filter(c, self.workSet))
+
+    @property
+    def FreezeWorkSet(self):
+        c = lambda n: n.Degree < self.K and self.MoveRelated(n)
+        return set(filter(c, self.workSet))
+
+    @property
+    def SimplifyWorkSet(self):
+        c = lambda n: n.Degree < self.K and not self.MoveRelated(n)
+        return set(filter(c, self.workSet))
+
+    def makeWorkList(self):
+        """ Divide initial nodes into worklists """
+        self.selectStack = []
+
+        # Fill initial move set:
+        for m in self.moves:
+            self.worklistMoves.add(m)
+
+    def Simplify(self):
+        """ 2. Remove nodes from the graph """
+        n = first(self.SimplifyWorkSet)
+        self.workSet.remove(n)
+        self.selectStack.append(n)
+        # Pop out of graph:
+        self.f.ig.delNode(n)
+
+    def EnableMoves(self, nodes):
+        for n in nodes:
+            for m in self.NodeMoves(n):
+                if m in self.activeMoves:
+                    self.activeMoves.remove(m)
+                    self.worklistMoves.add(m)
+                
+    def Coalesc(self):
+        """ Coalesc conservative. """
+        m = first(self.worklistMoves)
+        x = self.Node(m.dst[0])
+        y = self.Node(m.src[0])
+        u, v = (y, x) if y in self.precolored else (x, y)
+        self.worklistMoves.remove(m)
+        if u is v:
+            self.coalescedMoves.add(m)
+        elif v in self.precolored or self.f.ig.hasEdge(u, v):
+            self.constrainedMoves.add(m)
+        elif u not in self.precolored and self.Conservative(u, v):
+            self.coalescedMoves.add(m)
+            self.workSet.remove(v)
+            self.f.ig.Combine(u, v)
+        else:
+            self.activeMoves.add(m)
+        
+    def Conservative(self, u, v):
+        """ Briggs conservative criteria for coalesc """
+        nodes = u.Adjecent | v.Adjecent
+        c = lambda n: n.Degree >= self.K
+        k = len(list(filter(c, nodes)))
+        return k < self.K
+
+    def Freeze(self):
+        """ Give up coalescing on some node """
+        u = first(self.FreezeWorkSet)
+        self.freezeMoves(u)
+
+    def freezeMoves(self, u):
+        """ Freeze moves for node u """
+        for m in self.NodeMoves(u):
+            if m in self.activeMoves:
+                self.activeMoves.remove(m)
+            else:
+                sekf.worklistMoves.remove(m)
+            self.frozenMoves.add(m)
+            # Check other part of the move for still being move related:
+            v = m.src[0] if u is m.dst[0] else m.dst[0]
+    
+    def SelectSpill(self):
+        # TODO
+        pass
+
+    def AssignColors(self):
+        """ Add nodes back to the graph to color it. """
+        # Add nodes back to the graph: 
+        while self.selectStack:
+            n = self.selectStack.pop(-1)
+            self.f.ig.addNode(n)
+            takenregs = set(self.color[m] for m in n.Adjecent)
+            okColors = self.regs - takenregs
+            if okColors:
+                self.color[n] = first(okColors)
+                n.color = self.color[n]
+            else:
+                raise NotImplementedError('Spill required here!')
+        
+    def ApplyColors(self):
+        # Remove coalesced moves:
+        for mv in self.coalescedMoves:
+            self.f.instructions.remove(mv)
+
+        # Use allocated registers:
+        lookup = lambda t: self.color[self.Node(t)]
+        for i in self.f.instructions:
+            i.src = tuple(map(lookup, i.src))
+            i.dst = tuple(map(lookup, i.dst))
+
+    def allocFrame(self, f):
+        """ Do iterated register allocation for a single stack frame. """
+        self.InitData(f)
+        self.Build()
+        self.makeWorkList()
+        while True:
+            if self.SimplifyWorkSet:
+                self.Simplify()
+            elif self.worklistMoves:
+                self.Coalesc()
+            elif self.FreezeWorkSet:
+                self.Freeze()
+            elif self.SpillWorkSet:
+                raise NotImplementedError('Spill not implemented')
+            else:
+                break # Done!
+        self.AssignColors()
+        self.ApplyColors()
+