diff --git a/include/llvm/Support/IntegersSubset.h b/include/llvm/Support/IntegersSubset.h
index ac4eb97..998cc73 100644
--- a/include/llvm/Support/IntegersSubset.h
+++ b/include/llvm/Support/IntegersSubset.h
@@ -1,4 +1,4 @@
-//===-- llvm/ConstantRangesSet.h - The constant set of ranges ---*- C++ -*-===//
+//===-- llvm/IntegersSubset.h - The subset of integers ----------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -9,10 +9,9 @@
 //
 /// @file
 /// This file contains class that implements constant set of ranges:
-/// [<Low0,High0>,...,<LowN,HighN>]. Mainly, this set is used by SwitchInst and
-/// represents case value that may contain multiple ranges for a single
-/// successor.
-///
+/// [<Low0,High0>,...,<LowN,HighN>]. Initially, this class was created for
+/// SwitchInst and was used for case value representation that may contain
+/// multiple ranges for a single successor.
 //
 //===----------------------------------------------------------------------===//
 
@@ -280,7 +279,9 @@
   typedef std::list<IntTy> FlatCollectionTy;
   typedef std::pair<IntTy*, IntTy*> RangeLinkTy;
   typedef SmallVector<RangeLinkTy, 64> RangeLinksTy;
-  typedef typename RangeLinksTy::iterator RangeLinksConstIt;
+  typedef typename RangeLinksTy::const_iterator RangeLinksConstIt;
+  
+  typedef IntegersSubsetGeneric<IntTy> self;
   
 protected:
   
@@ -304,6 +305,26 @@
     }
   }
   
+  IntegersSubsetGeneric(const self& RHS) {
+    *this = RHS;
+  }
+  
+  self& operator=(const self& RHS) {
+    FlatCollection.clear();
+    RangeLinks.clear();
+    for (RangeLinksConstIt i = RHS.RangeLinks.begin(), e = RHS.RangeLinks.end();
+         i != e; ++i) {
+      RangeLinkTy RangeLink;
+      FlatCollection.push_back(*(i->first));
+      RangeLink.first = &FlatCollection.back();
+      if (i->first != i->second)
+        FlatCollection.push_back(*(i->second));
+      RangeLink.second = &FlatCollection.back();
+      RangeLinks.push_back(RangeLink);
+    }
+    return *this;
+  }
+  
   typedef IntRange<IntTy> Range;
  
   /// Checks is the given constant satisfies this case. Returns
@@ -314,8 +335,8 @@
       if (RangeLinks[i].first == RangeLinks[i].second) {
         if (*RangeLinks[i].first == CheckingVal)
           return true;
-      } else if (*RangeLinks[i].first >= CheckingVal &&
-                 *RangeLinks[i].second <= CheckingVal) 
+      } else if (*RangeLinks[i].first <= CheckingVal &&
+                 *RangeLinks[i].second >= CheckingVal) 
         return true;
     }
     return false;    
@@ -357,7 +378,7 @@
     for (unsigned i = 0, e = getNumItems(); i != e; ++i) {
       const APInt &Low = getItem(i).getLow();
       const APInt &High = getItem(i).getHigh();
-      const APInt &S = High - Low;
+      APInt S = High - Low + 1;
       sz += S;
     }
     return sz.getZExtValue();    
@@ -372,12 +393,12 @@
     for (unsigned i = 0, e = getNumItems(); i != e; ++i) {
       const APInt &Low = getItem(i).getLow();
       const APInt &High = getItem(i).getHigh();      
-      const APInt& S = High - Low;
+      APInt S = High - Low + 1;
       APInt oldSz = sz;
       sz += S;
-      if (oldSz.uge(i) && sz.ult(i)) {
+      if (sz.ugt(idx)) {
         APInt Res = Low;
-        APInt Offset(oldSz.getBitWidth(), i);
+        APInt Offset(oldSz.getBitWidth(), idx);
         Offset -= oldSz;
         Res += Offset;
         return Res;
diff --git a/include/llvm/Support/IntegersSubsetMapping.h b/include/llvm/Support/IntegersSubsetMapping.h
index b630119..d3d11f0 100644
--- a/include/llvm/Support/IntegersSubsetMapping.h
+++ b/include/llvm/Support/IntegersSubsetMapping.h
@@ -1,4 +1,4 @@
-//===- CRSBuilder.h - ConstantRangesSet Builder -----------------*- C++ -*-===//
+//===- IntegersSubsetMapping.h - Mapping subset ==> Successor ---*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -8,11 +8,12 @@
 //===----------------------------------------------------------------------===//
 //
 /// @file
-/// CRSBuilder allows to build and parse ConstantRangesSet objects.
-/// There is such features like add/remove range, or combine
-/// Two ConstantRangesSet object with neighboring ranges merging.
-/// Set IsReadonly=true if you want to operate with "const ConstantInt" and
-/// "const ConstantRangesSet" objects.
+/// IntegersSubsetMapping is mapping from A to B, where
+/// Items in A is subsets of integers,
+/// Items in B some pointers (Successors).
+/// If user which to add another subset for successor that is already
+/// exists in mapping, IntegersSubsetMapping merges existing subset with
+/// added one.
 //
 //===----------------------------------------------------------------------===//
 
@@ -55,6 +56,7 @@
   typedef std::list<RangeTy> RangesCollection;
   typedef typename RangesCollection::iterator RangesCollectionIt;
   
+  // TODO: Change unclean CRS prefixes to SubsetMap for example.
   typedef std::map<SuccessorClass*, RangesCollection > CRSMap;
   typedef typename CRSMap::iterator CRSMapIt;
 
@@ -112,7 +114,7 @@
     sort();
     for (CaseItemIt i = Items.begin(), j = i+1, e = Items.end();
          j != e; i = j++) {
-      if (isIntersected(j, i) && j->second != i->second) {
+      if (isIntersected(i, j) && i->second != j->second) {
         errItem = j;
         return false;
       }
@@ -173,7 +175,7 @@
   }  
   
   /// Adds all ranges and values from given ranges set to the current
-  /// CRSBuilder object.
+  /// mapping.
   void add(const IntegersSubset &CRS, SuccessorClass *S = 0) {
     for (unsigned i = 0, e = CRS.getNumItems(); i < e; ++i) {
       RangeTy R = CRS.getItem(i);
diff --git a/unittests/Support/IntegersSubsetTest.cpp b/unittests/Support/IntegersSubsetTest.cpp
new file mode 100644
index 0000000..5de1f7c
--- /dev/null
+++ b/unittests/Support/IntegersSubsetTest.cpp
@@ -0,0 +1,180 @@
+//===- llvm/unittest/Support/IntegersSubsetTest.cpp - IntegersSubset tests ===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/APInt.h"
+#include "llvm/Support/IntegersSubset.h" 
+#include "llvm/Support/IntegersSubsetMapping.h"
+
+#include "gtest/gtest.h"
+
+#include <vector>
+
+using namespace llvm;
+
+namespace {
+  
+  class Int : public APInt {
+  public:
+    Int(uint64_t V) : APInt(64, V) {}
+    bool operator < (const APInt& RHS) const { return ult(RHS); }
+    bool operator > (const APInt& RHS) const { return ugt(RHS); }
+    bool operator <= (const APInt& RHS) const { return ule(RHS); }
+    bool operator >= (const APInt& RHS) const { return uge(RHS); }
+  };
+  
+  typedef IntRange<Int> Range;
+  typedef IntegersSubsetGeneric<Int> Subset;
+  typedef IntegersSubsetMapping<unsigned,Subset,Int> Mapping;
+  
+  TEST(IntegersSubsetTest, GeneralTest) {
+    
+    // Test construction.
+
+    std::vector<Range> Ranges;
+    Ranges.reserve(3);
+
+    // Initialize Subset as union of three pairs:
+    // { {0, 8}, {10, 18}, {20, 28} }
+    for (unsigned i = 0; i < 3; ++i)
+      Ranges.push_back(Range(Int(i*10), Int(i*10 + 8)));
+
+    Subset TheSubset(Ranges);
+    
+    for (unsigned i = 0; i < 3; ++i) {
+      EXPECT_EQ(TheSubset.getItem(i).getLow(), Int(i*10));
+      EXPECT_EQ(TheSubset.getItem(i).getHigh(), Int(i*10 + 8));
+    }
+    
+    EXPECT_EQ(TheSubset.getNumItems(), 3ULL);
+    
+    // Test belonging to range.
+    
+    EXPECT_TRUE(TheSubset.isSatisfies(Int(5)));
+    EXPECT_FALSE(TheSubset.isSatisfies(Int(9)));
+    
+    // Test when subset contains the only item.
+    
+    Ranges.clear();
+    Ranges.push_back(Range(Int(10), Int(10)));
+    
+    Subset TheSingleNumber(Ranges);
+    
+    EXPECT_TRUE(TheSingleNumber.isSingleNumber());
+    
+    Ranges.push_back(Range(Int(12), Int(15)));
+    
+    Subset NotASingleNumber(Ranges);
+    
+    EXPECT_FALSE(NotASingleNumber.isSingleNumber());
+    
+    // Test when subset contains items that are not a ranges but
+    // the single numbers.
+    
+    Ranges.clear();
+    Ranges.push_back(Range(Int(10), Int(10)));
+    Ranges.push_back(Range(Int(15), Int(19)));
+    
+    Subset WithSingleNumberItems(Ranges);
+    
+    EXPECT_TRUE(WithSingleNumberItems.isSingleNumber(0));
+    EXPECT_FALSE(WithSingleNumberItems.isSingleNumber(1));
+    
+    // Test size of subset. Note subset itself may be not optimized (improper),
+    // so it may contain duplicates, and the size of subset { {0, 9} {5, 9} }
+    // will 15 instead of 10.
+    
+    Ranges.clear();
+    Ranges.push_back(Range(Int(0), Int(9)));
+    Ranges.push_back(Range(Int(5), Int(9)));
+    
+    Subset NotOptimizedSubset(Ranges);
+    
+    EXPECT_EQ(NotOptimizedSubset.getSize(), 15ULL);
+
+    // Test access to a single value.
+    // getSingleValue(idx) method represents subset as flat numbers collection,
+    // so subset { {0, 3}, {8, 10} } will represented as array
+    // { 0, 1, 2, 3, 8, 9, 10 }.
+    
+    Ranges.clear();
+    Ranges.push_back(Range(Int(0), Int(3)));
+    Ranges.push_back(Range(Int(8), Int(10)));
+    
+    Subset OneMoreSubset(Ranges);
+    
+    EXPECT_EQ(OneMoreSubset.getSingleValue(5), Int(9));
+  }
+  
+  TEST(IntegersSubsetTest, MappingTest) {
+
+    Mapping::Cases TheCases;
+    
+    unsigned Successors[3] = {0, 1, 2};
+    
+    // Test construction.
+    
+    Mapping TheMapping;
+    for (unsigned i = 0; i < 3; ++i)
+      TheMapping.add(Int(10*i), Int(10*i + 9), Successors + i);
+    TheMapping.add(Int(111), Int(222), Successors);
+    TheMapping.removeItem(--TheMapping.end());
+    
+    TheMapping.getCases(TheCases);
+    
+    EXPECT_EQ(TheCases.size(), 3ULL);
+    
+    for (unsigned i = 0; i < 3; ++i) {
+      Mapping::Cases::iterator CaseIt = TheCases.begin();
+      std::advance(CaseIt, i);  
+      EXPECT_EQ(CaseIt->first, Successors + i);
+      EXPECT_EQ(CaseIt->second.getNumItems(), 1ULL);
+      EXPECT_EQ(CaseIt->second.getItem(0), Range(Int(10*i), Int(10*i + 9)));
+    }
+    
+    // Test verification.
+    
+    Mapping ImproperMapping;
+    ImproperMapping.add(Int(10), Int(11), Successors + 0);
+    ImproperMapping.add(Int(11), Int(12), Successors + 1);
+    
+    Mapping::RangeIterator ErrItem;
+    EXPECT_FALSE(ImproperMapping.verify(ErrItem));
+    EXPECT_EQ(ErrItem, --ImproperMapping.end());
+    
+    Mapping ProperMapping;
+    ProperMapping.add(Int(10), Int(11), Successors + 0);
+    ProperMapping.add(Int(12), Int(13), Successors + 1);
+    
+    EXPECT_TRUE(ProperMapping.verify(ErrItem));
+    
+    // Test optimization.
+    
+    Mapping ToBeOptimized;
+    
+    for (unsigned i = 0; i < 3; ++i) {
+      ToBeOptimized.add(Int(i * 10), Int(i * 10 + 1), Successors + i);
+      ToBeOptimized.add(Int(i * 10 + 2), Int(i * 10 + 9), Successors + i);
+    }
+    
+    ToBeOptimized.optimize();
+    
+    TheCases.clear();
+    ToBeOptimized.getCases(TheCases);
+    
+    EXPECT_EQ(TheCases.size(), 3ULL);
+    
+    for (unsigned i = 0; i < 3; ++i) {
+      Mapping::Cases::iterator CaseIt = TheCases.begin();
+      std::advance(CaseIt, i);  
+      EXPECT_EQ(CaseIt->first, Successors + i);
+      EXPECT_EQ(CaseIt->second.getNumItems(), 1ULL);
+      EXPECT_EQ(CaseIt->second.getItem(0), Range(Int(i * 10), Int(i * 10 + 9)));
+    }
+  }
+}