LLVM  9.0.0svn
IntEqClasses.h
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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 
25 namespace llvm {
26 
27 class 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.
34 
35  /// NumClasses - The number of equivalence classes when compressed, or 0 when
36  /// uncompressed.
37  unsigned NumClasses;
38 
39 public:
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
unsigned operator[](unsigned a) const
operator[] - Return a's equivalence class number, 0 .
Definition: IntEqClasses.h:75
unsigned findLeader(unsigned a) const
findLeader - Compute the leader of a's equivalence class.
void grow(unsigned N)
grow - Increase capacity to hold 0 .
This class represents lattice values for constants.
Definition: AllocatorList.h:23
IntEqClasses(unsigned N=0)
IntEqClasses - Create an equivalence class mapping for 0 .. N-1.
Definition: IntEqClasses.h:41
void compress()
compress - Compress equivalence classes by numbering them 0 .
void clear()
clear - Clear all classes so that grow() will assign a unique class to every integer.
Definition: IntEqClasses.h:50
void uncompress()
uncompress - Change back to the uncompressed representation that allows editing.
unsigned getNumClasses() const
getNumClasses - Return the number of equivalence classes after compress() was called.
Definition: IntEqClasses.h:71
unsigned join(unsigned a, unsigned b)
Join the equivalence classes of a and b.
#define N
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())