[turbofan] break link between split use intervals

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/zone-containers.h"
 
@@ skipping 128 matching lines @@
 
   LifetimePosition start() const { return start_; }
   void set_start(LifetimePosition start) { start_ = start; }
   LifetimePosition end() const { return end_; }
   void set_end(LifetimePosition end) { end_ = end; }
   UseInterval* next() const { return next_; }
   void set_next(UseInterval* next) { next_ = next; }
 
   // Split this interval at the given position without effecting the
   // live range that owns it. The interval must contain the position.
-  void SplitAt(LifetimePosition pos, Zone* zone);
+  UseInterval* SplitAt(LifetimePosition pos, Zone* zone);
 
   // If this interval intersects with other return smallest position
   // that belongs to both of them.
   LifetimePosition Intersect(const UseInterval* other) const {
     if (other->start().Value() < start_.Value()) return other->Intersect(this);
     if (other->start().Value() < end_.Value()) return other->start();
     return LifetimePosition::Invalid();
   }
 
   bool Contains(LifetimePosition point) const {
@@ skipping 174 matching lines @@
 
   // Add a new interval or a new use position to this live range.
   void EnsureInterval(LifetimePosition start, LifetimePosition end, Zone* zone);
   void AddUseInterval(LifetimePosition start, LifetimePosition end, Zone* zone);
   void AddUsePosition(LifetimePosition pos, InstructionOperand* operand,
                       InstructionOperand* hint, Zone* zone);
 
   // Shorten the most recently added interval by setting a new start.
   void ShortenTo(LifetimePosition start);
 
-  // True if target overlaps an existing interval.
-  bool HasOverlap(UseInterval* target) const;
   void Verify() const;
 
   void ConvertUsesToOperand(const InstructionOperand& op,
                             InstructionOperand* spill_op);
 
   void set_kind(RegisterKind kind) { kind_ = kind; }
 
  private:
   struct SpillAtDefinitionList;
 
@@ skipping 438 matching lines @@
   RegisterAllocationData* const data_;
 
   DISALLOW_COPY_AND_ASSIGN(LiveRangeConnector);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_REGISTER_ALLOCATOR_H_