Make CTX allocatable by the register allocator.

runtime/vm/flow_graph_allocator.h

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_FLOW_GRAPH_ALLOCATOR_H_
 #define VM_FLOW_GRAPH_ALLOCATOR_H_
 
 #include "vm/flow_graph.h"
 #include "vm/growable_array.h"
 #include "vm/intermediate_language.h"
@@ skipping 111 matching lines @@
                         Definition* def,
                         intptr_t vreg,
                         bool output_same_as_first_input,
                         Location* in_ref,
                         Definition* input,
                         intptr_t input_vreg,
                         BitVector* interference_set);
   void ProcessOneInstruction(BlockEntryInstr* block,
                              Instruction* instr,
                              BitVector* interference_set);
+
+  static const intptr_t kNormalEntryPos = 2;
+
   void ProcessInitialDefinition(Definition* defn,
                                 LiveRange* range,
                                 BlockEntryInstr* block);
   void ConnectIncomingPhiMoves(JoinEntryInstr* join);
   void BlockLocation(Location loc, intptr_t from, intptr_t to);
   void BlockRegisterLocation(Location loc,
                              intptr_t from,
                              intptr_t to,
                              bool* blocked_registers,
                              LiveRange** blocking_ranges);
@@ skipping 527 matching lines @@
 
   AllocationFinger finger_;
 
   DISALLOW_COPY_AND_ASSIGN(LiveRange);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_ALLOCATOR_H_