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
CFGSCC__anona1dcc4750111::CFGSCC39 CFGSCC() : FunctionPass(ID) {}
40 bool runOnFunction(Function& func) override;
41
print__anona1dcc4750111::CFGSCC42 void print(raw_ostream &O, const Module* = nullptr) const override { }
43
getAnalysisUsage__anona1dcc4750111::CFGSCC44 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
CallGraphSCC__anona1dcc4750111::CallGraphSCC51 CallGraphSCC() : ModulePass(ID) {}
52
53 // run - Print out SCCs in the call graph for the specified module.
54 bool runOnModule(Module &M) override;
55
print__anona1dcc4750111::CallGraphSCC56 void print(raw_ostream &O, const Module* = nullptr) const override { }
57
58 // getAnalysisUsage - This pass requires the CallGraph.
getAnalysisUsage__anona1dcc4750111::CallGraphSCC59 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
runOnFunction(Function & F)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.
runOnModule(Module & M)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 }
112