//===- llvm-extract.cpp - LLVM function extraction utility ----------------===//
//
//                     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 utility changes the input module to only contain a single function,
// which is primarily used for debugging transformations.
//
//===----------------------------------------------------------------------===//

#include "llvm/Module.h"
#include "llvm/PassManager.h"
#include "llvm/Bitcode/ReaderWriter.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ManagedStatic.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/System/Signals.h"
#include <iostream>
#include <memory>
#include <fstream>
using namespace llvm;

// InputFilename - The filename to read from.
static cl::opt<std::string>
InputFilename(cl::Positional, cl::desc("<input bytecode file>"),
              cl::init("-"), cl::value_desc("filename"));

static cl::opt<std::string>
OutputFilename("o", cl::desc("Specify output filename"),
               cl::value_desc("filename"), cl::init("-"));

static cl::opt<bool>
Force("f", cl::desc("Overwrite output files"));

static cl::opt<bool>
DeleteFn("delete", cl::desc("Delete specified function from Module"));

static cl::opt<bool>
Relink("relink",
       cl::desc("Turn external linkage for callees of function to delete"));

// ExtractFunc - The function to extract from the module... defaults to main.
static cl::opt<std::string>
ExtractFunc("func", cl::desc("Specify function to extract"), cl::init("main"),
            cl::value_desc("function"));

int main(int argc, char **argv) {
  llvm_shutdown_obj X;  // Call llvm_shutdown() on exit.
  cl::ParseCommandLineOptions(argc, argv, " llvm extractor\n");
  sys::PrintStackTraceOnErrorSignal();

  std::auto_ptr<Module> M;
  
  MemoryBuffer *Buffer = MemoryBuffer::getFileOrSTDIN(InputFilename);
  if (Buffer == 0) {
    cerr << "Error reading file '" + InputFilename + "'";
    return 1;
  } else {
    M.reset(ParseBitcodeFile(Buffer));
  }
  delete Buffer;
  
  if (M.get() == 0) {
    cerr << argv[0] << ": bytecode didn't read correctly.\n";
    return 1;
  }

  // Figure out which function we should extract
  Function *F = M.get()->getFunction(ExtractFunc);
  if (F == 0) {
    cerr << argv[0] << ": program doesn't contain function named '"
         << ExtractFunc << "'!\n";
    return 1;
  }

  // In addition to deleting all other functions, we also want to spiff it
  // up a little bit.  Do this now.
  PassManager Passes;
  Passes.add(new TargetData(M.get())); // Use correct TargetData
  // Either isolate the function or delete it from the Module
  Passes.add(createFunctionExtractionPass(F, DeleteFn, Relink));
  if (!DeleteFn)
    Passes.add(createGlobalDCEPass());           // Delete unreachable globals
  Passes.add(createDeadTypeEliminationPass());   // Remove dead types...
  Passes.add(createStripDeadPrototypesPass());   // Remove dead func decls

  std::ostream *Out = 0;

  if (OutputFilename != "-") {  // Not stdout?
    if (!Force && std::ifstream(OutputFilename.c_str())) {
      // If force is not specified, make sure not to overwrite a file!
      cerr << argv[0] << ": error opening '" << OutputFilename
           << "': file exists!\n"
           << "Use -f command line argument to force output\n";
      return 1;
    }
    std::ios::openmode io_mode = std::ios::out | std::ios::trunc |
                                 std::ios::binary;
    Out = new std::ofstream(OutputFilename.c_str(), io_mode);
  } else {                      // Specified stdout
    // FIXME: cout is not binary!
    Out = &std::cout;
  }

  Passes.add(CreateBitcodeWriterPass(*Out));
  Passes.run(*M.get());

  if (Out != &std::cout)
    delete Out;
  return 0;
}