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