lib/Transforms/Hello/Hello.cpp

   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/raw_ostream.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       errs() << "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       errs() << "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)");