[turbofan] LiveRange splinter merging optimizations.

src/compiler/register-allocator.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_REGISTER_ALLOCATOR_H_
 #define V8_REGISTER_ALLOCATOR_H_
 
 #include "src/compiler/instruction.h"
 #include "src/ostreams.h"
 #include "src/zone-containers.h"
@@ skipping 527 matching lines @@
   int GetNextChildId() { return ++last_child_id_; }
   bool IsSpilledOnlyInDeferredBlocks() const {
     return spilled_in_deferred_blocks_;
   }
 
   struct SpillAtDefinitionList;
 
   SpillAtDefinitionList* spills_at_definition() const {
     return spills_at_definition_;
   }
+  void set_last_child(LiveRange* range) { last_child_ = range; }
+  LiveRange* last_child() const { return last_child_; }
 
  private:
   typedef BitField<bool, 1, 1> HasSlotUseField;
   typedef BitField<bool, 2, 1> IsPhiField;
   typedef BitField<bool, 3, 1> IsNonLoopPhiField;
   typedef BitField<SpillType, 4, 2> SpillTypeField;
 
-  LiveRange* GetLastChild();
-
   int vreg_;
   int last_child_id_;
   TopLevelLiveRange* splintered_from_;
   union {
     // Correct value determined by spill_type()
     InstructionOperand* spill_operand_;
     SpillRange* spill_range_;
   };
   SpillAtDefinitionList* spills_at_definition_;
   // TODO(mtrofin): generalize spilling after definition, currently specialized
   // just for spill in a single deferred block.
   bool spilled_in_deferred_blocks_;
   int spill_start_index_;
+  LiveRange* last_child_;
+  LiveRange* last_insertion_point_;
 
   DISALLOW_COPY_AND_ASSIGN(TopLevelLiveRange);
 };
 
 
 struct PrintableLiveRange {
   const RegisterConfiguration* register_configuration_;
   const LiveRange* range_;
 };
 
@@ skipping 463 matching lines @@
   RegisterAllocationData* const data_;
 
   DISALLOW_COPY_AND_ASSIGN(LiveRangeConnector);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_REGISTER_ALLOCATOR_H_