Use BitVector instead of handcrafted SparseSet.

src/hydrogen-gvn.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 18 matching lines @@
 #define V8_HYDROGEN_GVN_H_
 
 #include "hydrogen.h"
 #include "hydrogen-instructions.h"
 #include "compiler.h"
 #include "zone.h"
 
 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:
   explicit HGlobalValueNumberingPhase(HGraph* graph);
 
   void Run() {
     Analyze();
     // Trigger a second analysis pass to further eliminate duplicate values
     // that could only be discovered by removing side-effect-generating
     // instructions during the first pass.
@@ skipping 22 matching lines @@
   bool removed_side_effects_;
 
   // A map of block IDs to their side effects.
   ZoneList<GVNFlagSet> block_side_effects_;
 
   // A map of loop header block IDs to their loop's side effects.
   ZoneList<GVNFlagSet> loop_side_effects_;
 
   // Used when collecting side effects on paths from dominator to
   // dominated.
-  SparseSet visited_on_paths_;
+  BitVector visited_on_paths_;
 
   DISALLOW_COPY_AND_ASSIGN(HGlobalValueNumberingPhase);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_GVN_H_