tools/bugpoint/FindBugs.cpp

   1 //===-- FindBugs.cpp - Run Many Different Optimizations -------------------===//
   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 defines an interface that allows bugpoint to choose different
  11 // combinations of optimizations to run on the selected input. Bugpoint will
  12 // run these optimizations and record the success/failure of each. This way
  13 // we can hopefully spot bugs in the optimizations.
  14 //
  15 //===----------------------------------------------------------------------===//
  16
  17 #include "BugDriver.h"
  18 #include "ToolRunner.h"
  19 #include "llvm/Pass.h"
  20 #include "llvm/Support/FileSystem.h"
  21 #include "llvm/Support/raw_ostream.h"
  22 #include <algorithm>
  23 #include <ctime>
  24 #include <random>
  25 using namespace llvm;
  26
  27 Error
  28 BugDriver::runManyPasses(const std::vector<std::string> &AllPasses) {
  29   setPassesToRun(AllPasses);
  30   outs() << "Starting bug finding procedure...\n\n";
  31
  32   // Creating a reference output if necessary
  33   if (Error E = initializeExecutionEnvironment())
  34     return E;
  35
  36   outs() << "\n";
  37   if (ReferenceOutputFile.empty()) {
  38     outs() << "Generating reference output from raw program: \n";
  39     if (Error E = createReferenceFile(Program))
  40       return E;
  41   }
  42
  43   std::mt19937 randomness(std::random_device{}());
  44   unsigned num = 1;
  45   while (1) {
  46     //
  47     // Step 1: Randomize the order of the optimizer passes.
  48     //
  49     std::shuffle(PassesToRun.begin(), PassesToRun.end(), randomness);
  50
  51     //
  52     // Step 2: Run optimizer passes on the program and check for success.
  53     //
  54     outs() << "Running selected passes on program to test for crash: ";
  55     for (int i = 0, e = PassesToRun.size(); i != e; i++) {
  56       outs() << "-" << PassesToRun[i] << " ";
  57     }
  58
  59     std::string Filename;
  60     if (runPasses(Program, PassesToRun, Filename, false)) {
  61       outs() << "\n";
  62       outs() << "Optimizer passes caused failure!\n\n";
  63       return debugOptimizerCrash();
  64     } else {
  65       outs() << "Combination " << num << " optimized successfully!\n";
  66     }
  67
  68     //
  69     // Step 3: Compile the optimized code.
  70     //
  71     outs() << "Running the code generator to test for a crash: ";
  72     if (Error E = compileProgram(Program)) {
  73       outs() << "\n*** compileProgram threw an exception: ";
  74       outs() << toString(std::move(E));
  75       return debugCodeGeneratorCrash();
  76     }
  77     outs() << '\n';
  78
  79     //
  80     // Step 4: Run the program and compare its output to the reference
  81     // output (created above).
  82     //
  83     outs() << "*** Checking if passes caused miscompliation:\n";
  84     Expected<bool> Diff = diffProgram(Program, Filename, "", false);
  85     if (Error E = Diff.takeError()) {
  86       errs() << toString(std::move(E));
  87       return debugCodeGeneratorCrash();
  88     }
  89     if (*Diff) {
  90       outs() << "\n*** diffProgram returned true!\n";
  91       Error E = debugMiscompilation();
  92       if (!E)
  93         return Error::success();
  94     }
  95     outs() << "\n*** diff'd output matches!\n";
  96
  97     sys::fs::remove(Filename);
  98
  99     outs() << "\n\n";
 100     num++;
 101   } // end while
 102
 103   // Unreachable.
 104 }