tools/opt/PrintSCC.cpp

   1 //===- PrintSCC.cpp - Enumerate SCCs in some key graphs -------------------===//
   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 provides passes to print out SCCs in a CFG or a CallGraph.
  11 // Normally, you would not use these passes; instead, you would use the
  12 // scc_iterator directly to enumerate SCCs and process them in some way.  These
  13 // passes serve three purposes:
  14 //
  15 // (1) As a reference for how to use the scc_iterator.
  16 // (2) To print out the SCCs for a CFG or a CallGraph:
  17 //       analyze -print-cfg-sccs            to print the SCCs in each CFG of a module.
  18 //       analyze -print-cfg-sccs -stats     to print the #SCCs and the maximum SCC size.
  19 //       analyze -print-cfg-sccs -debug > /dev/null to watch the algorithm in action.
  20 //
  21 //     and similarly:
  22 //       analyze -print-callgraph-sccs [-stats] [-debug] to print SCCs in the CallGraph
  23 //
  24 // (3) To test the scc_iterator.
  25 //
  26 //===----------------------------------------------------------------------===//
  27
  28 #include "llvm/ADT/SCCIterator.h"
  29 #include "llvm/Analysis/CallGraph.h"
  30 #include "llvm/IR/CFG.h"
  31 #include "llvm/IR/Module.h"
  32 #include "llvm/Pass.h"
  33 #include "llvm/Support/raw_ostream.h"
  34 using namespace llvm;
  35
  36 namespace {
  37   struct CFGSCC : public FunctionPass {
  38     static char ID;  // Pass identification, replacement for typeid
  39     CFGSCC() : FunctionPass(ID) {}
  40     bool runOnFunction(Function& func) override;
  41
  42     void print(raw_ostream &O, const Module* = nullptr) const override { }
  43
  44     void getAnalysisUsage(AnalysisUsage &AU) const override {
  45       AU.setPreservesAll();
  46     }
  47   };
  48
  49   struct CallGraphSCC : public ModulePass {
  50     static char ID;  // Pass identification, replacement for typeid
  51     CallGraphSCC() : ModulePass(ID) {}
  52
  53     // run - Print out SCCs in the call graph for the specified module.
  54     bool runOnModule(Module &M) override;
  55
  56     void print(raw_ostream &O, const Module* = nullptr) const override { }
  57
  58     // getAnalysisUsage - This pass requires the CallGraph.
  59     void getAnalysisUsage(AnalysisUsage &AU) const override {
  60       AU.setPreservesAll();
  61       AU.addRequired<CallGraphWrapperPass>();
  62     }
  63   };
  64 }
  65
  66 char CFGSCC::ID = 0;
  67 static RegisterPass<CFGSCC>
  68 Y("print-cfg-sccs", "Print SCCs of each function CFG");
  69
  70 char CallGraphSCC::ID = 0;
  71 static RegisterPass<CallGraphSCC>
  72 Z("print-callgraph-sccs", "Print SCCs of the Call Graph");
  73
  74 bool CFGSCC::runOnFunction(Function &F) {
  75   unsigned sccNum = 0;
  76   errs() << "SCCs for Function " << F.getName() << " in PostOrder:";
  77   for (scc_iterator<Function*> SCCI = scc_begin(&F); !SCCI.isAtEnd(); ++SCCI) {
  78     const std::vector<BasicBlock *> &nextSCC = *SCCI;
  79     errs() << "\nSCC #" << ++sccNum << " : ";
  80     for (std::vector<BasicBlock*>::const_iterator I = nextSCC.begin(),
  81            E = nextSCC.end(); I != E; ++I)
  82       errs() << (*I)->getName() << ", ";
  83     if (nextSCC.size() == 1 && SCCI.hasLoop())
  84       errs() << " (Has self-loop).";
  85   }
  86   errs() << "\n";
  87
  88   return true;
  89 }
  90
  91
  92 // run - Print out SCCs in the call graph for the specified module.
  93 bool CallGraphSCC::runOnModule(Module &M) {
  94   CallGraph &CG = getAnalysis<CallGraphWrapperPass>().getCallGraph();
  95   unsigned sccNum = 0;
  96   errs() << "SCCs for the program in PostOrder:";
  97   for (scc_iterator<CallGraph*> SCCI = scc_begin(&CG); !SCCI.isAtEnd();
  98        ++SCCI) {
  99     const std::vector<CallGraphNode*> &nextSCC = *SCCI;
 100     errs() << "\nSCC #" << ++sccNum << " : ";
 101     for (std::vector<CallGraphNode*>::const_iterator I = nextSCC.begin(),
 102            E = nextSCC.end(); I != E; ++I)
 103       errs() << ((*I)->getFunction() ? (*I)->getFunction()->getName()
 104                                      : "external node") << ", ";
 105     if (nextSCC.size() == 1 && SCCI.hasLoop())
 106       errs() << " (Has self-loop).";
 107   }
 108   errs() << "\n";
 109
 110   return true;
 111 }