Use BitVector instead of handcrafted SparseSet.

src/hydrogen-gvn.h

Index: src/hydrogen-gvn.h
diff --git a/src/hydrogen-gvn.h b/src/hydrogen-gvn.h
index 66224e43381ac75c944bbf18691509341513edce..64a0fec76bf7db030ac9f09c34bb3a4af7bfbd27 100644
--- a/src/hydrogen-gvn.h
+++ b/src/hydrogen-gvn.h
@@ -36,46 +36,6 @@
 namespace v8 {
 namespace internal {
 
-// Simple sparse set with O(1) add, contains, and clear.
-class SparseSet {
- public:
-  SparseSet(Zone* zone, int capacity)
-      : capacity_(capacity),
-        length_(0),
-        dense_(zone->NewArray<int>(capacity)),
-        sparse_(zone->NewArray<int>(capacity)) {
-#ifndef NVALGRIND
-    // Initialize the sparse array to make valgrind happy.
-    memset(sparse_, 0, sizeof(sparse_[0]) * capacity);
-#endif
-  }
-
-  bool Contains(int n) const {
-    ASSERT(0 <= n && n < capacity_);
-    int d = sparse_[n];
-    return 0 <= d && d < length_ && dense_[d] == n;
-  }
-
-  bool Add(int n) {
-    if (Contains(n)) return false;
-    dense_[length_] = n;
-    sparse_[n] = length_;
-    ++length_;
-    return true;
-  }
-
-  void Clear() { length_ = 0; }
-
- private:
-  int capacity_;
-  int length_;
-  int* dense_;
-  int* sparse_;
-
-  DISALLOW_COPY_AND_ASSIGN(SparseSet);
-};
-
-
 // Perform common subexpression elimination and loop-invariant code motion.
 class HGlobalValueNumberingPhase : public HPhase {
  public:
@@ -118,7 +78,7 @@ class HGlobalValueNumberingPhase : public HPhase {
 
   // Used when collecting side effects on paths from dominator to
   // dominated.
-  SparseSet visited_on_paths_;
+  BitVector visited_on_paths_;
 
   DISALLOW_COPY_AND_ASSIGN(HGlobalValueNumberingPhase);
 };