VM: Move representation selection code out of the flow graph optimizer.

runtime/vm/flow_graph.h

Index: runtime/vm/flow_graph.h
diff --git a/runtime/vm/flow_graph.h b/runtime/vm/flow_graph.h
index 9841716092a0e2373e60b1cb04d799d2b0539510..5ca3d0f2ab1981e083e40bbfbc6ad581efe2cb63 100644
--- a/runtime/vm/flow_graph.h
+++ b/runtime/vm/flow_graph.h
@@ -296,6 +296,16 @@ class FlowGraph : public ZoneAllocated {
   intptr_t inlining_id() const { return inlining_id_; }
   void set_inlining_id(intptr_t value) { inlining_id_ = value; }
 
+  // Returns true if any instructions were canonicalized away.
+  bool Canonicalize();
+
+  void SelectRepresentations();
+
+  void WidenSmiToInt32();
+
+  // Remove environments from the instructions which do not deoptimize.
+  void EliminateEnvironments();
+
  private:
   friend class IfConverter;
   friend class BranchSimplifier;
@@ -340,6 +350,14 @@ class FlowGraph : public ZoneAllocated {
   // indicates membership in the loop.
   BitVector* FindLoop(BlockEntryInstr* m, BlockEntryInstr* n) const;
 
+  void InsertConversionsFor(Definition* def);
+  void ConvertUse(Value* use, Representation from);
+  void ConvertEnvironmentUse(Value* use, Representation from);
+  void InsertConversion(Representation from,
+                        Representation to,
+                        Value* use,
+                        bool is_environment_use);
+
   Thread* thread_;
 
   // DiscoverBlocks computes parent_ and assigned_vars_ which are then used