llvm / llvm-project / bf317f66989cac26e17b4cd16ab1c7bdfe73dbe0 / . / llvm / include / llvm / ADT / IntEqClasses.h

//===-- llvm/ADT/IntEqClasses.h - Equiv. Classes of Integers ----*- C++ -*-===// | |

// | |

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. | |

// See https://llvm.org/LICENSE.txt for license information. | |

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception | |

// | |

//===----------------------------------------------------------------------===// | |

// | |

// Equivalence classes for small integers. This is a mapping of the integers | |

// 0 .. N-1 into M equivalence classes numbered 0 .. M-1. | |

// | |

// Initially each integer has its own equivalence class. Classes are joined by | |

// passing a representative member of each class to join(). | |

// | |

// Once the classes are built, compress() will number them 0 .. M-1 and prevent | |

// further changes. | |

// | |

//===----------------------------------------------------------------------===// | |

#ifndef LLVM_ADT_INTEQCLASSES_H | |

#define LLVM_ADT_INTEQCLASSES_H | |

#include "llvm/ADT/SmallVector.h" | |

namespace llvm { | |

class IntEqClasses { | |

/// EC - When uncompressed, map each integer to a smaller member of its | |

/// equivalence class. The class leader is the smallest member and maps to | |

/// itself. | |

/// | |

/// When compressed, EC[i] is the equivalence class of i. | |

SmallVector<unsigned, 8> EC; | |

/// NumClasses - The number of equivalence classes when compressed, or 0 when | |

/// uncompressed. | |

unsigned NumClasses; | |

public: | |

/// IntEqClasses - Create an equivalence class mapping for 0 .. N-1. | |

IntEqClasses(unsigned N = 0) : NumClasses(0) { grow(N); } | |

/// grow - Increase capacity to hold 0 .. N-1, putting new integers in unique | |

/// equivalence classes. | |

/// This requires an uncompressed map. | |

void grow(unsigned N); | |

/// clear - Clear all classes so that grow() will assign a unique class to | |

/// every integer. | |

void clear() { | |

EC.clear(); | |

NumClasses = 0; | |

} | |

/// Join the equivalence classes of a and b. After joining classes, | |

/// findLeader(a) == findLeader(b). This requires an uncompressed map. | |

/// Returns the new leader. | |

unsigned join(unsigned a, unsigned b); | |

/// findLeader - Compute the leader of a's equivalence class. This is the | |

/// smallest member of the class. | |

/// This requires an uncompressed map. | |

unsigned findLeader(unsigned a) const; | |

/// compress - Compress equivalence classes by numbering them 0 .. M. | |

/// This makes the equivalence class map immutable. | |

void compress(); | |

/// getNumClasses - Return the number of equivalence classes after compress() | |

/// was called. | |

unsigned getNumClasses() const { return NumClasses; } | |

/// operator[] - Return a's equivalence class number, 0 .. getNumClasses()-1. | |

/// This requires a compressed map. | |

unsigned operator[](unsigned a) const { | |

assert(NumClasses && "operator[] called before compress()"); | |

return EC[a]; | |

} | |

/// uncompress - Change back to the uncompressed representation that allows | |

/// editing. | |

void uncompress(); | |

}; | |

} // End llvm namespace | |

#endif |