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       1             : //===-- llvm/ADT/IntEqClasses.h - Equiv. Classes of Integers ----*- C++ -*-===//
       2             : //
       3             : //                     The LLVM Compiler Infrastructure
       4             : //
       5             : // This file is distributed under the University of Illinois Open Source
       6             : // License. See LICENSE.TXT for details.
       7             : //
       8             : //===----------------------------------------------------------------------===//
       9             : //
      10             : // Equivalence classes for small integers. This is a mapping of the integers
      11             : // 0 .. N-1 into M equivalence classes numbered 0 .. M-1.
      12             : //
      13             : // Initially each integer has its own equivalence class. Classes are joined by
      14             : // passing a representative member of each class to join().
      15             : //
      16             : // Once the classes are built, compress() will number them 0 .. M-1 and prevent
      17             : // further changes.
      18             : //
      19             : //===----------------------------------------------------------------------===//
      20             : 
      21             : #ifndef LLVM_ADT_INTEQCLASSES_H
      22             : #define LLVM_ADT_INTEQCLASSES_H
      23             : 
      24             : #include "llvm/ADT/SmallVector.h"
      25             : 
      26             : namespace llvm {
      27             : 
      28       72250 : class IntEqClasses {
      29             :   /// EC - When uncompressed, map each integer to a smaller member of its
      30             :   /// equivalence class. The class leader is the smallest member and maps to
      31             :   /// itself.
      32             :   ///
      33             :   /// When compressed, EC[i] is the equivalence class of i.
      34             :   SmallVector<unsigned, 8> EC;
      35             : 
      36             :   /// NumClasses - The number of equivalence classes when compressed, or 0 when
      37             :   /// uncompressed.
      38             :   unsigned NumClasses;
      39             : 
      40             : public:
      41             :   /// IntEqClasses - Create an equivalence class mapping for 0 .. N-1.
      42     3627022 :   IntEqClasses(unsigned N = 0) : NumClasses(0) { grow(N); }
      43             : 
      44             :   /// grow - Increase capacity to hold 0 .. N-1, putting new integers in unique
      45             :   /// equivalence classes.
      46             :   /// This requires an uncompressed map.
      47             :   void grow(unsigned N);
      48             : 
      49             :   /// clear - Clear all classes so that grow() will assign a unique class to
      50             :   /// every integer.
      51             :   void clear() {
      52             :     EC.clear();
      53     2347423 :     NumClasses = 0;
      54             :   }
      55             : 
      56             :   /// Join the equivalence classes of a and b. After joining classes,
      57             :   /// findLeader(a) == findLeader(b). This requires an uncompressed map.
      58             :   /// Returns the new leader.
      59             :   unsigned join(unsigned a, unsigned b);
      60             : 
      61             :   /// findLeader - Compute the leader of a's equivalence class. This is the
      62             :   /// smallest member of the class.
      63             :   /// This requires an uncompressed map.
      64             :   unsigned findLeader(unsigned a) const;
      65             : 
      66             :   /// compress - Compress equivalence classes by numbering them 0 .. M.
      67             :   /// This makes the equivalence class map immutable.
      68             :   void compress();
      69             : 
      70             :   /// getNumClasses - Return the number of equivalence classes after compress()
      71             :   /// was called.
      72           0 :   unsigned getNumClasses() const { return NumClasses; }
      73             : 
      74             :   /// operator[] - Return a's equivalence class number, 0 .. getNumClasses()-1.
      75             :   /// This requires a compressed map.
      76             :   unsigned operator[](unsigned a) const {
      77             :     assert(NumClasses && "operator[] called before compress()");
      78    37195249 :     return EC[a];
      79             :   }
      80             : 
      81             :   /// uncompress - Change back to the uncompressed representation that allows
      82             :   /// editing.
      83             :   void uncompress();
      84             : };
      85             : 
      86             : } // End llvm namespace
      87             : 
      88             : #endif