CallGraphSCCPass.h revision 314564 
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/Analysis/CallGraph.h"
25#include "llvm/Pass.h"
26#include "llvm/PassSupport.h"
27
28namespace llvm {
29
30class CallGraphNode;
31class CallGraph;
32class PMStack;
33class CallGraphSCC;
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 &O,
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  ///
61  virtual bool runOnSCC(CallGraphSCC &SCC) = 0;
62
63  /// doFinalization - This method is called after the SCC's of the program has
64  /// been processed, allowing the pass to do final cleanup as necessary.
65  virtual bool doFinalization(CallGraph &CG) {
66    return false;
67  }
68
69  /// Assign pass manager to manager this pass
70  void assignPassManager(PMStack &PMS, PassManagerType PMT) override;
71
72  ///  Return what kind of Pass Manager can manage this pass.
73  PassManagerType getPotentialPassManagerType() const override {
74    return PMT_CallGraphPassManager;
75  }
76
77  /// getAnalysisUsage - For this class, we declare that we require and preserve
78  /// the call graph.  If the derived class implements this method, it should
79  /// always explicitly call the implementation here.
80  void getAnalysisUsage(AnalysisUsage &Info) const override;
81
82protected:
83  /// Optional passes call this function to check whether the pass should be
84  /// skipped. This is the case when optimization bisect is over the limit.
85  bool skipSCC(CallGraphSCC &SCC) const;
86};
87
88/// CallGraphSCC - This is a single SCC that a CallGraphSCCPass is run on.
89class CallGraphSCC {
90  const CallGraph &CG; // The call graph for this SCC.
91  void *Context; // The CGPassManager object that is vending this.
92  std::vector<CallGraphNode*> Nodes;
93
94public:
95  CallGraphSCC(CallGraph &cg, void *context) : CG(cg), Context(context) {}
96
97  void initialize(ArrayRef<CallGraphNode *> NewNodes) {
98    Nodes.assign(NewNodes.begin(), NewNodes.end());
99  }
100
101  bool isSingular() const { return Nodes.size() == 1; }
102  unsigned size() const { return Nodes.size(); }
103
104  /// ReplaceNode - This informs the SCC and the pass manager that the specified
105  /// Old node has been deleted, and New is to be used in its place.
106  void ReplaceNode(CallGraphNode *Old, CallGraphNode *New);
107
108  typedef std::vector<CallGraphNode *>::const_iterator iterator;
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  DummyCGSCCPass() : CallGraphSCCPass(ID) {
123    PassRegistry &Registry = *PassRegistry::getPassRegistry();
124    initializeDummyCGSCCPassPass(Registry);
125  };
126  bool runOnSCC(CallGraphSCC &SCC) override { return false; }
127  void getAnalysisUsage(AnalysisUsage &AU) const override {
128    AU.setPreservesAll();
129  }
130};
131
132} // End llvm namespace
133
134#endif
135