Implement local check elimination on basic blocks.

src/unique.h

 // Copyright 2013 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 144 matching lines @@
         array_[i] = uniq;
         size_++;
         return;
       }
     }
     // Append the element to the the end.
     Grow(size_ + 1, zone);
     array_[size_++] = uniq;
   }
 
+  // Remove an element from this set. Mutates this set. O(|this|)
+  void Remove(Unique<T> uniq) {
+    for (int i = 0; i < size_; i++) {
+      if (array_[i] == uniq) {
+        while (++i < size_) array_[i - 1] = array_[i];
+        size_--;
+        return;
+      }
+    }
+  }
+
   // Compare this set against another set. O(|this|).
   bool Equals(UniqueSet<T>* that) const {
     if (that->size_ != this->size_) return false;
     for (int i = 0; i < this->size_; i++) {
       if (this->array_[i] != that->array_[i]) return false;
     }
     return true;
   }
 
   template <typename U>
@@ skipping 83 matching lines @@
   // Makes an exact copy of this set. O(|this| + |that|).
   UniqueSet<T>* Copy(Zone* zone) const {
     UniqueSet<T>* copy = new(zone) UniqueSet<T>();
     copy->size_ = this->size_;
     copy->capacity_ = this->size_;
     copy->array_ = zone->NewArray<Unique<T> >(this->size_);
     memcpy(copy->array_, this->array_, this->size_ * sizeof(Unique<T>));
     return copy;
   }
 
+  void Clear() {
+    size_ = 0;
+  }
+
   inline int size() const {
     return size_;
   }
 
   inline Unique<T> at(int index) const {
     ASSERT(index >= 0 && index < size_);
     return array_[index];
   }
 
  private:
@@ skipping 18 matching lines @@
       capacity_ = new_capacity;
       array_ = new_array;
     }
   }
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_UNIQUE_H_