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 }
100