Make CTX allocatable by the register allocator.

runtime/vm/intermediate_language.h

Index: runtime/vm/intermediate_language.h
===================================================================
--- runtime/vm/intermediate_language.h	(revision 41279)
+++ runtime/vm/intermediate_language.h	(working copy)
@@ -726,7 +726,7 @@
     locs_ = MakeLocationSummary(isolate, optimizing);
   }
 
-  static LocationSummary* MakeCallSummary();
+  static LocationSummary* MakeCallSummary(Isolate* isolate);
 
   virtual void EmitNativeCode(FlowGraphCompiler* compiler) {
     UNIMPLEMENTED();
@@ -1318,7 +1318,7 @@
 
   ZoneGrowableArray<PhiInstr*>* phis() const { return phis_; }
 
-  void InsertPhi(intptr_t var_index, intptr_t var_count);
+  void InsertPhi(intptr_t var_index, intptr_t var_count, bool always_live);
   void RemoveDeadPhis(Definition* replacement);
 
   void InsertPhi(PhiInstr* phi);
@@ -2583,19 +2583,28 @@
 };
 
 
-class ClosureCallInstr : public TemplateDefinition<1> {
+class ClosureCallInstr : public TemplateDefinition<2> {
  public:
+  enum {
+    kFunctionPos = 0,
+    kContextPos = 1
+  };
+
   ClosureCallInstr(Value* function,
+                   Value* context,
                    ClosureCallNode* node,
                    ZoneGrowableArray<PushArgumentInstr*>* arguments)
-      : TemplateDefinition<1>(Isolate::Current()->GetNextDeoptId()),
+      : TemplateDefinition<2>(Isolate::Current()->GetNextDeoptId()),
         ast_node_(*node),
         arguments_(arguments) {
-    SetInputAt(0, function);
+    SetInputAt(kFunctionPos, function);
+    SetInputAt(kContextPos, context);
   }
 
   DECLARE_INSTRUCTION(ClosureCall)
 
+  Value* context() const { return InputAt(kContextPos); }
+
   const Array& argument_names() const { return ast_node_.arguments()->names(); }
   virtual intptr_t token_pos() const { return ast_node_.token_pos(); }