Remember required register kind when creating artificial virtual register.

src/data-flow.h

 // Copyright 2010 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 94 matching lines @@
   static int SizeFor(int length) {
     return 1 + ((length - 1) / 32);
   }
 
   BitVector& operator=(const BitVector& rhs) {
     if (this != &rhs) CopyFrom(rhs);
     return *this;
   }
 
   void CopyFrom(const BitVector& other) {
-    ASSERT(other.length() == length());
-    for (int i = 0; i < data_length_; i++) {
+    ASSERT(other.length() <= length());
+    for (int i = 0; i < other.data_length_; i++) {
       data_[i] = other.data_[i];
     }
+    for (int i = other.data_length_; i < data_length_; i++) {
+      data_[i] = 0;
+    }
   }
 
   bool Contains(int i) const {
     ASSERT(i >= 0 && i < length());
     uint32_t block = data_[i / 32];
     return (block & (1U << (i % 32))) != 0;
   }
 
   void Add(int i) {
     ASSERT(i >= 0 && i < length());
@@ skipping 238 matching lines @@
   BitVector av_;
 
   DISALLOW_COPY_AND_ASSIGN(AssignedVariablesAnalyzer);
 };
 
 
 } }  // namespace v8::internal
 
 
 #endif  // V8_DATAFLOW_H_