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 
28 namespace llvm {
29 
30 class CallGraph;
31 class CallGraphNode;
32 class CallGraphSCC;
33 class PMStack;
34 
35 class CallGraphSCCPass : public Pass {
36 public:
CallGraphSCCPass(char & pid)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.
doInitialization(CallGraph & CG)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.
doFinalization(CallGraph & CG)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.
getPotentialPassManagerType()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 
81 protected:
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.
88 class 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 
93 public:
CallGraphSCC(CallGraph & cg,void * context)94   CallGraphSCC(CallGraph &cg, void *context) : CG(cg), Context(context) {}
95 
initialize(ArrayRef<CallGraphNode * > NewNodes)96   void initialize(ArrayRef<CallGraphNode *> NewNodes) {
97     Nodes.assign(NewNodes.begin(), NewNodes.end());
98   }
99 
isSingular()100   bool isSingular() const { return Nodes.size() == 1; }
size()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 
begin()109   iterator begin() const { return Nodes.begin(); }
end()110   iterator end() const { return Nodes.end(); }
111 
getCallGraph()112   const CallGraph &getCallGraph() { return CG; }
113 };
114 
115 void initializeDummyCGSCCPassPass(PassRegistry &);
116 
117 /// This pass is required by interprocedural register allocation. It forces
118 /// codegen to follow bottom up order on call graph.
119 class DummyCGSCCPass : public CallGraphSCCPass {
120 public:
121   static char ID;
122 
DummyCGSCCPass()123   DummyCGSCCPass() : CallGraphSCCPass(ID) {
124     PassRegistry &Registry = *PassRegistry::getPassRegistry();
125     initializeDummyCGSCCPassPass(Registry);
126   }
127 
runOnSCC(CallGraphSCC & SCC)128   bool runOnSCC(CallGraphSCC &SCC) override { return false; }
129 
getAnalysisUsage(AnalysisUsage & AU)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