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/Support/raw_ostream.h"
19#include "llvm/ADT/Statistic.h"
20using namespace llvm;
21
22STATISTIC(HelloCounter, "Counts number of functions greeted");
23
24namespace {
25  // Hello - The first implementation, without getAnalysisUsage.
26  struct Hello : public FunctionPass {
27    static char ID; // Pass identification, replacement for typeid
28    Hello() : FunctionPass(ID) {}
29
30    virtual bool runOnFunction(Function &F) {
31      ++HelloCounter;
32      errs() << "Hello: ";
33      errs().write_escaped(F.getName()) << '\n';
34      return false;
35    }
36  };
37}
38
39char Hello::ID = 0;
40static RegisterPass<Hello> X("hello", "Hello World Pass");
41
42namespace {
43  // Hello2 - The second implementation with getAnalysisUsage implemented.
44  struct Hello2 : public FunctionPass {
45    static char ID; // Pass identification, replacement for typeid
46    Hello2() : FunctionPass(ID) {}
47
48    virtual bool runOnFunction(Function &F) {
49      ++HelloCounter;
50      errs() << "Hello: ";
51      errs().write_escaped(F.getName()) << '\n';
52      return false;
53    }
54
55    // We don't modify the program, so we preserve all analyses
56    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
57      AU.setPreservesAll();
58    }
59  };
60}
61
62char Hello2::ID = 0;
63static RegisterPass<Hello2>
64Y("hello2", "Hello World Pass (with getAnalysisUsage implemented)");
65