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      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 
     27 namespace llvm {
     28 
     29 class CallGraph;
     30 class CallGraphNode;
     31 class CallGraphSCC;
     32 class PMStack;
     33 
     34 class CallGraphSCCPass : public Pass {
     35 public:
     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 
     80 protected:
     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.
     87 class 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 
     92 public:
     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   /// DeleteNode - This informs the SCC and the pass manager that the specified
    107   /// Old node has been deleted.
    108   void DeleteNode(CallGraphNode *Old);
    109 
    110   using iterator = std::vector<CallGraphNode *>::const_iterator;
    111 
    112   iterator begin() const { return Nodes.begin(); }
    113   iterator end() const { return Nodes.end(); }
    114 
    115   const CallGraph &getCallGraph() { return CG; }
    116 };
    117 
    118 void initializeDummyCGSCCPassPass(PassRegistry &);
    119 
    120 /// This pass is required by interprocedural register allocation. It forces
    121 /// codegen to follow bottom up order on call graph.
    122 class DummyCGSCCPass : public CallGraphSCCPass {
    123 public:
    124   static char ID;
    125 
    126   DummyCGSCCPass() : CallGraphSCCPass(ID) {
    127     PassRegistry &Registry = *PassRegistry::getPassRegistry();
    128     initializeDummyCGSCCPassPass(Registry);
    129   }
    130 
    131   bool runOnSCC(CallGraphSCC &SCC) override { return false; }
    132 
    133   void getAnalysisUsage(AnalysisUsage &AU) const override {
    134     AU.setPreservesAll();
    135   }
    136 };
    137 
    138 } // end namespace llvm
    139 
    140 #endif // LLVM_ANALYSIS_CALLGRAPHSCCPASS_H
    141