Cache first hint operand while building live ranges.

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 311 matching lines @@
   // All uses following the given position will be moved from this
   // live range to the result live range.
   void SplitAt(LifetimePosition position, LiveRange* result, Zone* zone);
 
   bool IsDouble() const { return is_double_; }
   bool HasRegisterAssigned() const {
     return assigned_register_ != kInvalidAssignment;
   }
   bool IsSpilled() const { return spilled_; }
 
+  LOperand* current_hint_operand() const {
+    ASSERT(current_hint_operand_ == FirstHint());
+    return current_hint_operand_;
+  }
   LOperand* FirstHint() const {
     UsePosition* pos = first_pos_;
     while (pos != NULL && !pos->HasHint()) pos = pos->next();
     if (pos != NULL) return pos->hint();
     return NULL;
   }
 
   LifetimePosition Start() const {
     ASSERT(!IsEmpty());
     return first_interval()->start();
@@ skipping 49 matching lines @@
   bool is_double_;
   int assigned_register_;
   UseInterval* last_interval_;
   UseInterval* first_interval_;
   UsePosition* first_pos_;
   LiveRange* parent_;
   LiveRange* next_;
   // This is used as a cache, it doesn't affect correctness.
   mutable UseInterval* current_interval_;
   UsePosition* last_processed_use_;
+  // This is used as a cache, it's invalid outside of BuildLiveRanges.
+  LOperand* current_hint_operand_;
   LOperand* spill_operand_;
   int spill_start_index_;
 };
 
 
 class LAllocator BASE_EMBEDDED {
  public:
   LAllocator(int first_virtual_register, HGraph* graph);
 
   static void TraceAlloc(const char* msg, ...);
@@ skipping 225 matching lines @@
   LifetimePosition allocation_finger_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(LAllocator);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_LITHIUM_ALLOCATOR_H_