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/Pass.h"
29#include "llvm/Module.h"
30#include "llvm/Analysis/CallGraph.h"
31#include "llvm/Support/CFG.h"
32#include "llvm/Support/raw_ostream.h"
33#include "llvm/ADT/SCCIterator.h"
34using namespace llvm;
35
36namespace {
37  struct CFGSCC : public FunctionPass {
38    static char ID;  // Pass identification, replacement for typeid
39    CFGSCC() : FunctionPass(ID) {}
40    bool runOnFunction(Function& func);
41
42    void print(raw_ostream &O, const Module* = 0) const { }
43
44    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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);
55
56    void print(raw_ostream &O, const Module* = 0) const { }
57
58    // getAnalysisUsage - This pass requires the CallGraph.
59    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
60      AU.setPreservesAll();
61      AU.addRequired<CallGraph>();
62    }
63  };
64}
65
66char CFGSCC::ID = 0;
67static RegisterPass<CFGSCC>
68Y("print-cfg-sccs", "Print SCCs of each function CFG");
69
70char CallGraphSCC::ID = 0;
71static RegisterPass<CallGraphSCC>
72Z("print-callgraph-sccs", "Print SCCs of the Call Graph");
73
74bool 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),
78         E = scc_end(&F); SCCI != E; ++SCCI) {
79    std::vector<BasicBlock*> &nextSCC = *SCCI;
80    errs() << "\nSCC #" << ++sccNum << " : ";
81    for (std::vector<BasicBlock*>::const_iterator I = nextSCC.begin(),
82           E = nextSCC.end(); I != E; ++I)
83      errs() << (*I)->getName() << ", ";
84    if (nextSCC.size() == 1 && SCCI.hasLoop())
85      errs() << " (Has self-loop).";
86  }
87  errs() << "\n";
88
89  return true;
90}
91
92
93// run - Print out SCCs in the call graph for the specified module.
94bool CallGraphSCC::runOnModule(Module &M) {
95  CallGraphNode* rootNode = getAnalysis<CallGraph>().getRoot();
96  unsigned sccNum = 0;
97  errs() << "SCCs for the program in PostOrder:";
98  for (scc_iterator<CallGraphNode*> SCCI = scc_begin(rootNode),
99         E = scc_end(rootNode); SCCI != E; ++SCCI) {
100    const std::vector<CallGraphNode*> &nextSCC = *SCCI;
101    errs() << "\nSCC #" << ++sccNum << " : ";
102    for (std::vector<CallGraphNode*>::const_iterator I = nextSCC.begin(),
103           E = nextSCC.end(); I != E; ++I)
104      errs() << ((*I)->getFunction() ? (*I)->getFunction()->getName()
105                                     : "external node") << ", ";
106    if (nextSCC.size() == 1 && SCCI.hasLoop())
107      errs() << " (Has self-loop).";
108  }
109  errs() << "\n";
110
111  return true;
112}
113