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/Support/raw_ostream.h"
  19 #include "llvm/ADT/Statistic.h"
  20 using namespace llvm;
  21
  22 STATISTIC(HelloCounter, "Counts number of functions greeted");
  23
  24 namespace {
  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
  39 char Hello::ID = 0;
  40 static RegisterPass<Hello> X("hello", "Hello World Pass");
  41
  42 namespace {
  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
  62 char Hello2::ID = 0;
  63 static RegisterPass<Hello2>
  64 Y("hello2", "Hello World Pass (with getAnalysisUsage implemented)");