Set previous instruction pointers when building the graph.

runtime/vm/intermediate_language.h

 // Copyright (c) 2012, 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_INTERMEDIATE_LANGUAGE_H_
 #define VM_INTERMEDIATE_LANGUAGE_H_
 
 #include "vm/allocation.h"
 #include "vm/ast.h"
 #include "vm/growable_array.h"
@@ skipping 334 matching lines @@
     ASSERT(!IsControl());
     ASSERT(!IsPhi());
     ASSERT(instr == NULL || !instr->IsBlockEntry());
     // TODO(fschneider): Also add Throw and ReThrow to the list of instructions
     // that do not have a successor. Currently, the graph builder will continue
     // to append instruction in case of a Throw inside an expression. This
     // condition should be handled in the graph builder
     next_ = instr;
   }
 
+  // Link together two instruction.
+  void LinkTo(Instruction* next) {
+    ASSERT(this != next);
+    this->set_next(next);
+    next->set_previous(this);
+  }
+
   // Removed this instruction from the graph.
   Instruction* RemoveFromGraph(bool return_previous = true);
 
   // Normal instructions can have 0 (inside a block) or 1 (last instruction in
   // a block) successors. Branch instruction with >1 successors override this
   // function.
   virtual intptr_t SuccessorCount() const;
   virtual BlockEntryInstr* SuccessorAt(intptr_t index) const;
 
   void Goto(JoinEntryInstr* entry);
@@ skipping 3736 matching lines @@
   ForwardInstructionIterator* current_iterator_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FlowGraphVisitor);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_