1 //===- Hello.cpp - Example code from "Writing an LLVM Pass" ---------------===//
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 implements two versions of the LLVM "Hello World" pass described
11 // in docs/WritingAnLLVMPass.html
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #define DEBUG_TYPE "hello"
16 #include "llvm/Pass.h"
17 #include "llvm/Function.h"
18 #include "llvm/ADT/StringExtras.h"
19 #include "llvm/Support/Streams.h"
20 #include "llvm/ADT/Statistic.h"
21 using namespace llvm;
22 
23 STATISTIC(HelloCounter, "Counts number of functions greeted");
24 
25 namespace {
26   // Hello - The first implementation, without getAnalysisUsage.
27   struct Hello : public FunctionPass {
28     static char ID; // Pass identification, replacement for typeid
29     Hello() : FunctionPass(&ID) {}
30 
31     virtual bool runOnFunction(Function &F) {
32       HelloCounter++;
33       std::string fname = F.getName();
34       EscapeString(fname);
35       cerr << "Hello: " << fname << "\n";
36       return false;
37     }
38   };
39 }
40 
41 char Hello::ID = 0;
42 static RegisterPass<Hello> X("hello", "Hello World Pass");
43 
44 namespace {
45   // Hello2 - The second implementation with getAnalysisUsage implemented.
46   struct Hello2 : public FunctionPass {
47     static char ID; // Pass identification, replacement for typeid
48     Hello2() : FunctionPass(&ID) {}
49 
50     virtual bool runOnFunction(Function &F) {
51       HelloCounter++;
52       std::string fname = F.getName();
53       EscapeString(fname);
54       cerr << "Hello: " << fname << "\n";
55       return false;
56     }
57 
58     // We don't modify the program, so we preserve all analyses
59     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
60       AU.setPreservesAll();
61     };
62   };
63 }
64 
65 char Hello2::ID = 0;
66 static RegisterPass<Hello2>
67 Y("hello2", "Hello World Pass (with getAnalysisUsage implemented)");
68