Fix a bug in liveness analysis code and add more comments.

runtime/vm/bit_vector.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_BIT_VECTOR_H_
 #define VM_BIT_VECTOR_H_
 
 #include "vm/allocation.h"
 #include "vm/isolate.h"
 #include "vm/zone.h"
@@ skipping 46 matching lines @@
   static intptr_t SizeFor(intptr_t length) {
     return 1 + ((length - 1) / kBitsPerWord);
   }
 
   void Add(intptr_t i) {
     ASSERT(i >= 0 && i < length());
     data_[i / kBitsPerWord] |= (static_cast<uword>(1) << (i % kBitsPerWord));
   }
 
   // Add all elements that are in the bitvector from.
-  bool AddAll(BitVector* from) {
-    ASSERT(data_length_ == from->data_length_);
-    bool changed = false;
-    for (intptr_t i = 0; i < data_length_; i++) {
-      const uword before = data_[i];
-      const uword after = data_[i] | from->data_[i];
-      if (before != after) changed = true;
-      data_[i] = after;
-    }
-    return changed;
-  }
+  bool AddAll(BitVector* from);
 
   // From the bitvector gen add those elements that are not in the
   // bitvector kill.
-  bool KillAndAdd(BitVector* kill, BitVector* gen) {
-    ASSERT(data_length_ == kill->data_length_);
-    ASSERT(data_length_ == gen->data_length_);
-    bool changed = false;
-    for (intptr_t i = 0; i < data_length_; i++) {
-      const uword before = data_[i];
-      const uword after = data_[i] | (gen->data_[i] & ~kill->data_[i]);
-      if (before != after) changed = true;
-      data_[i] = after;
-    }
-    return changed;
-  }
+  bool KillAndAdd(BitVector* kill, BitVector* gen);
 
   bool Contains(int i) const {
     ASSERT(i >= 0 && i < length());
     uword block = data_[i / kBitsPerWord];
     return (block & (static_cast<uword>(1) << (i % kBitsPerWord))) != 0;
   }
 
   void Clear() {
     for (intptr_t i = 0; i < data_length_; i++) {
       data_[i] = 0;
     }
   }
 
   intptr_t length() const { return length_; }
 
  private:
   intptr_t length_;
   intptr_t data_length_;
   uword* data_;
 
   DISALLOW_COPY_AND_ASSIGN(BitVector);
 };
 
 }  // namespace dart
 
 #endif  // VM_BIT_VECTOR_H_