Move LiveUnionArray into LiveIntervalUnion.h

It is useful outside RegAllocBase.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158041 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LiveIntervalUnion.h b/lib/CodeGen/LiveIntervalUnion.h
index 4925abf..cd4e690 100644
--- a/lib/CodeGen/LiveIntervalUnion.h
+++ b/lib/CodeGen/LiveIntervalUnion.h
@@ -181,6 +181,28 @@
     Query(const Query&);          // DO NOT IMPLEMENT
     void operator=(const Query&); // DO NOT IMPLEMENT
   };
+
+  // Array of LiveIntervalUnions.
+  class Array {
+    unsigned Size;
+    LiveIntervalUnion *LIUs;
+  public:
+    Array() : Size(0), LIUs(0) {}
+    ~Array() { clear(); }
+
+    // Initialize the array to have Size entries.
+    // Reuse an existing allocation if the size matches.
+    void init(LiveIntervalUnion::Allocator&, unsigned Size);
+
+    unsigned size() const { return Size; }
+
+    void clear();
+
+    LiveIntervalUnion& operator[](unsigned idx) {
+      assert(idx <  Size && "idx out of bounds");
+      return LIUs[idx];
+    }
+  };
 };
 
 } // end namespace llvm