tools/opt/PrintSCC.cpp

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