llvm/lib/Transforms/Hello/Hello.cpp

   1 //===- Hello.cpp - Example code from "Writing an LLVM Pass" ---------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file implements two versions of the LLVM "Hello World" pass described
  10 // in docs/WritingAnLLVMPass.html
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/ADT/Statistic.h"
  15 #include "llvm/IR/Function.h"
  16 #include "llvm/Pass.h"
  17 #include "llvm/Support/raw_ostream.h"
  18 using namespace llvm;
  19
  20 #define DEBUG_TYPE "hello"
  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     bool runOnFunction(Function &F) override {
  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     bool runOnFunction(Function &F) override {
  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     void getAnalysisUsage(AnalysisUsage &AU) const override {
  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)");