1//===- CallGraphSCCPass.h - Pass that operates BU on call graph -*- 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// This file defines the CallGraphSCCPass class, which is used for passes which
11// are implemented as bottom-up traversals on the call graph.  Because there may
12// be cycles in the call graph, passes of this type operate on the call-graph in
13// SCC order: that is, they process function bottom-up, except for recursive
14// functions, which they process all at once.
15//
16// These passes are inherently interprocedural, and are required to keep the
17// call graph up-to-date if they do anything which could modify it.
18//
19//===----------------------------------------------------------------------===//
20
21#ifndef LLVM_ANALYSIS_CALLGRAPHSCCPASS_H
22#define LLVM_ANALYSIS_CALLGRAPHSCCPASS_H
23
24#include "llvm/ADT/ArrayRef.h"
25#include "llvm/Pass.h"
26#include <vector>
27
28namespace llvm {
29
30class CallGraph;
31class CallGraphNode;
32class CallGraphSCC;
33class PMStack;
34
35class CallGraphSCCPass : public Pass {
36public:
37  explicit CallGraphSCCPass(char &pid) : Pass(PT_CallGraphSCC, pid) {}
38
39  /// createPrinterPass - Get a pass that prints the Module
40  /// corresponding to a CallGraph.
41  Pass *createPrinterPass(raw_ostream &OS,
42                          const std::string &Banner) const override;
43
44  using llvm::Pass::doInitialization;
45  using llvm::Pass::doFinalization;
46
47  /// doInitialization - This method is called before the SCC's of the program
48  /// has been processed, allowing the pass to do initialization as necessary.
49  virtual bool doInitialization(CallGraph &CG) {
50    return false;
51  }
52
53  /// runOnSCC - This method should be implemented by the subclass to perform
54  /// whatever action is necessary for the specified SCC.  Note that
55  /// non-recursive (or only self-recursive) functions will have an SCC size of
56  /// 1, where recursive portions of the call graph will have SCC size > 1.
57  ///
58  /// SCC passes that add or delete functions to the SCC are required to update
59  /// the SCC list, otherwise stale pointers may be dereferenced.
60  virtual bool runOnSCC(CallGraphSCC &SCC) = 0;
61
62  /// doFinalization - This method is called after the SCC's of the program has
63  /// been processed, allowing the pass to do final cleanup as necessary.
64  virtual bool doFinalization(CallGraph &CG) {
65    return false;
66  }
67
68  /// Assign pass manager to manager this pass
69  void assignPassManager(PMStack &PMS, PassManagerType PMT) override;
70
71  ///  Return what kind of Pass Manager can manage this pass.
72  PassManagerType getPotentialPassManagerType() const override {
73    return PMT_CallGraphPassManager;
74  }
75
76  /// getAnalysisUsage - For this class, we declare that we require and preserve
77  /// the call graph.  If the derived class implements this method, it should
78  /// always explicitly call the implementation here.
79  void getAnalysisUsage(AnalysisUsage &Info) const override;
80
81protected:
82  /// Optional passes call this function to check whether the pass should be
83  /// skipped. This is the case when optimization bisect is over the limit.
84  bool skipSCC(CallGraphSCC &SCC) const;
85};
86
87/// CallGraphSCC - This is a single SCC that a CallGraphSCCPass is run on.
88class CallGraphSCC {
89  const CallGraph &CG; // The call graph for this SCC.
90  void *Context; // The CGPassManager object that is vending this.
91  std::vector<CallGraphNode *> Nodes;
92
93public:
94  CallGraphSCC(CallGraph &cg, void *context) : CG(cg), Context(context) {}
95
96  void initialize(ArrayRef<CallGraphNode *> NewNodes) {
97    Nodes.assign(NewNodes.begin(), NewNodes.end());
98  }
99
100  bool isSingular() const { return Nodes.size() == 1; }
101  unsigned size() const { return Nodes.size(); }
102
103  /// ReplaceNode - This informs the SCC and the pass manager that the specified
104  /// Old node has been deleted, and New is to be used in its place.
105  void ReplaceNode(CallGraphNode *Old, CallGraphNode *New);
106
107  using iterator = std::vector<CallGraphNode *>::const_iterator;
108
109  iterator begin() const { return Nodes.begin(); }
110  iterator end() const { return Nodes.end(); }
111
112  const CallGraph &getCallGraph() { return CG; }
113};
114
115void initializeDummyCGSCCPassPass(PassRegistry &);
116
117/// This pass is required by interprocedural register allocation. It forces
118/// codegen to follow bottom up order on call graph.
119class DummyCGSCCPass : public CallGraphSCCPass {
120public:
121  static char ID;
122
123  DummyCGSCCPass() : CallGraphSCCPass(ID) {
124    PassRegistry &Registry = *PassRegistry::getPassRegistry();
125    initializeDummyCGSCCPassPass(Registry);
126  }
127
128  bool runOnSCC(CallGraphSCC &SCC) override { return false; }
129
130  void getAnalysisUsage(AnalysisUsage &AU) const override {
131    AU.setPreservesAll();
132  }
133};
134
135} // end namespace llvm
136
137#endif // LLVM_ANALYSIS_CALLGRAPHSCCPASS_H
138