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#include "llvm/ADT/Statistic.h"
16#include "llvm/IR/Function.h"
17#include "llvm/Pass.h"
18#include "llvm/Support/raw_ostream.h"
19using namespace llvm;
20
21#define DEBUG_TYPE "hello"
22
23STATISTIC(HelloCounter, "Counts number of functions greeted");
24
25namespace {
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    bool runOnFunction(Function &F) override {
32      ++HelloCounter;
33      errs() << "Hello: ";
34      errs().write_escaped(F.getName()) << '\n';
35      return false;
36    }
37  };
38}
39
40char Hello::ID = 0;
41static RegisterPass<Hello> X("hello", "Hello World Pass");
42
43namespace {
44  // Hello2 - The second implementation with getAnalysisUsage implemented.
45  struct Hello2 : public FunctionPass {
46    static char ID; // Pass identification, replacement for typeid
47    Hello2() : FunctionPass(ID) {}
48
49    bool runOnFunction(Function &F) override {
50      ++HelloCounter;
51      errs() << "Hello: ";
52      errs().write_escaped(F.getName()) << '\n';
53      return false;
54    }
55
56    // We don't modify the program, so we preserve all analyses.
57    void getAnalysisUsage(AnalysisUsage &AU) const override {
58      AU.setPreservesAll();
59    }
60  };
61}
62
63char Hello2::ID = 0;
64static RegisterPass<Hello2>
65Y("hello2", "Hello World Pass (with getAnalysisUsage implemented)");
66