1//===-- llvm/ADT/IntEqClasses.h - Equiv. Classes of Integers ----*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8///
9/// \file
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
26namespace llvm {
27
28class 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 = 0;
39
40public:
41 /// IntEqClasses - Create an equivalence class mapping for 0 .. N-1.
42 IntEqClasses(unsigned N = 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 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 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 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
89

source code of llvm/include/llvm/ADT/IntEqClasses.h