Make UsePosition::hint immutable.

src/lithium-allocator.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 226 matching lines @@
   LifetimePosition start_;
   LifetimePosition end_;
   UseInterval* next_;
 
   friend class LiveRange;  // Assigns to start_.
 };
 
 // Representation of a use position.
 class UsePosition: public ZoneObject {
  public:
-  UsePosition(LifetimePosition pos, LOperand* operand);
+  UsePosition(LifetimePosition pos, LOperand* operand, LOperand* hint);
 
   LOperand* operand() const { return operand_; }
   bool HasOperand() const { return operand_ != NULL; }
 
   LOperand* hint() const { return hint_; }
-  void set_hint(LOperand* hint) { hint_ = hint; }
   bool HasHint() const;
   bool RequiresRegister() const;
   bool RegisterIsBeneficial() const;
 
   LifetimePosition pos() const { return pos_; }
   UsePosition* next() const { return next_; }
 
  private:
   void set_next(UsePosition* next) { next_ = next; }
 
-  LOperand* operand_;
-  LOperand* hint_;
-  LifetimePosition pos_;
+  LOperand* const operand_;
+  LOperand* const hint_;
+  LifetimePosition const pos_;
   UsePosition* next_;
   bool requires_reg_;
   bool register_beneficial_;
 
   friend class LiveRange;
 };
 
 // Representation of SSA values' live ranges as a collection of (continuous)
 // intervals over the instruction ordering.
 class LiveRange: public ZoneObject {
@@ skipping 83 matching lines @@
   bool Covers(LifetimePosition position);
   LifetimePosition FirstIntersection(LiveRange* other);
 
   // 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);
-  UsePosition* AddUsePosition(LifetimePosition pos,
-                              LOperand* operand,
-                              Zone* zone);
+  void AddUsePosition(LifetimePosition pos,
+                      LOperand* operand,
+                      LOperand* hint,
+                      Zone* zone);
 
   // Shorten the most recently added interval by setting a new start.
   void ShortenTo(LifetimePosition start);
 
 #ifdef DEBUG
   // True if target overlaps an existing interval.
   bool HasOverlap(UseInterval* target) const;
   void Verify() const;
 #endif
 
@@ skipping 253 matching lines @@
   LifetimePosition allocation_finger_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(LAllocator);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_LITHIUM_ALLOCATOR_H_