Simple iterative liveness analysis over SSA.

runtime/vm/flow_graph_allocator.h

Index: runtime/vm/flow_graph_allocator.h
diff --git a/runtime/vm/flow_graph_allocator.h b/runtime/vm/flow_graph_allocator.h
index b70e12205dd23de67e8d27f7f3c411e7243663bd..bb6985fc74153e453cf851f105b96bd2904896d1 100644
--- a/runtime/vm/flow_graph_allocator.h
+++ b/runtime/vm/flow_graph_allocator.h
@@ -12,13 +12,26 @@ namespace dart {
 
 class FlowGraphAllocator : public ValueObject {
  public:
-  explicit FlowGraphAllocator(const GrowableArray<BlockEntryInstr*>& blocks)
-      : blocks_(blocks) { }
+  explicit FlowGraphAllocator(const GrowableArray<BlockEntryInstr*>& postorder,

[Florian Schneider, 2012/06/25 14:38:29]

No explicit necessary.

[Vyacheslav Egorov (Google), 2012/06/25 16:58:26]

Done.

+                              intptr_t max_ssa_temp_index);
 
   void ResolveConstraints();
 
+  void AnalyzeLiveness();
+
  private:
-  const GrowableArray<BlockEntryInstr*>& blocks_;
+  void ComputeKillAndGenSets();
+  bool UpdateLiveOut(BlockEntryInstr* instr);
+  bool UpdateLiveIn(BlockEntryInstr* instr);
+  void ComputeLiveInAndLiveOutSets();
+  void DumpLiveness();
+

[srdjan, 2012/06/25 17:30:05]

It woud be nice to have comments describing briefly which state is described by
which instance field, as long as the name does not describe itself.

+  GrowableArray<BitVector*> live_out_;
+  GrowableArray<BitVector*> kill_;
+  GrowableArray<BitVector*> gen_;
+  GrowableArray<BitVector*> live_in_;
+  const GrowableArray<BlockEntryInstr*>& postorder_;
+  const intptr_t vreg_count_;
 
   DISALLOW_COPY_AND_ASSIGN(FlowGraphAllocator);
 };