xref: /llvm-project-15.0.7/llvm/lib/Transforms/Hello/Hello.cpp (revision a7459ca8)

//===- Hello.cpp - Example code from "Writing an LLVM Pass" ---------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements two versions of the LLVM "Hello World" pass described
// in docs/WritingAnLLVMPass.html
//
//===----------------------------------------------------------------------===//

#include "llvm/Pass.h"
#include "llvm/Function.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/SlowOperationInformer.h"
#include "llvm/Support/Streams.h"
#include "llvm/ADT/Statistic.h"
using namespace llvm;

namespace {
  Statistic<int> HelloCounter("hellocount",
      "Counts number of functions greeted");
  // Hello - The first implementation, without getAnalysisUsage.
  struct Hello : public FunctionPass {
    virtual bool runOnFunction(Function &F) {
      SlowOperationInformer soi("EscapeString");
      HelloCounter++;
      std::string fname = F.getName();
      EscapeString(fname);
      llvm_cerr << "Hello: " << fname << "\n";
      return false;
    }
  };
  RegisterPass<Hello> X("hello", "Hello World Pass");

  // Hello2 - The second implementation with getAnalysisUsage implemented.
  struct Hello2 : public FunctionPass {
    virtual bool runOnFunction(Function &F) {
      SlowOperationInformer soi("EscapeString");
      HelloCounter++;
      std::string fname = F.getName();
      EscapeString(fname);
      llvm_cerr << "Hello: " << fname << "\n";
      return false;
    }

    // We don't modify the program, so we preserve all analyses
    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
      AU.setPreservesAll();
    };
  };
  RegisterPass<Hello2> Y("hello2",
                        "Hello World Pass (with getAnalysisUsage implemented)");
}