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