tools/bugpoint/FindBugs.cpp

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