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      1 //===- verify-uselistorder.cpp - The LLVM Modular Optimizer ---------------===//
      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 // Verify that use-list order can be serialized correctly.  After reading the
     11 // provided IR, this tool shuffles the use-lists and then writes and reads to a
     12 // separate Module whose use-list orders are compared to the original.
     13 //
     14 // The shuffles are deterministic, but guarantee that use-lists will change.
     15 // The algorithm per iteration is as follows:
     16 //
     17 //  1. Seed the random number generator.  The seed is different for each
     18 //     shuffle.  Shuffle 0 uses default+0, shuffle 1 uses default+1, and so on.
     19 //
     20 //  2. Visit every Value in a deterministic order.
     21 //
     22 //  3. Assign a random number to each Use in the Value's use-list in order.
     23 //
     24 //  4. If the numbers are already in order, reassign numbers until they aren't.
     25 //
     26 //  5. Sort the use-list using Value::sortUseList(), which is a stable sort.
     27 //
     28 //===----------------------------------------------------------------------===//
     29 
     30 #include "llvm/ADT/DenseMap.h"
     31 #include "llvm/ADT/DenseSet.h"
     32 #include "llvm/AsmParser/Parser.h"
     33 #include "llvm/Bitcode/ReaderWriter.h"
     34 #include "llvm/IR/LLVMContext.h"
     35 #include "llvm/IR/Module.h"
     36 #include "llvm/IR/UseListOrder.h"
     37 #include "llvm/IR/Verifier.h"
     38 #include "llvm/IRReader/IRReader.h"
     39 #include "llvm/Support/CommandLine.h"
     40 #include "llvm/Support/Debug.h"
     41 #include "llvm/Support/ErrorHandling.h"
     42 #include "llvm/Support/FileSystem.h"
     43 #include "llvm/Support/FileUtilities.h"
     44 #include "llvm/Support/ManagedStatic.h"
     45 #include "llvm/Support/MemoryBuffer.h"
     46 #include "llvm/Support/PrettyStackTrace.h"
     47 #include "llvm/Support/Signals.h"
     48 #include "llvm/Support/SourceMgr.h"
     49 #include "llvm/Support/SystemUtils.h"
     50 #include "llvm/Support/raw_ostream.h"
     51 #include <random>
     52 #include <vector>
     53 
     54 using namespace llvm;
     55 
     56 #define DEBUG_TYPE "uselistorder"
     57 
     58 static cl::opt<std::string> InputFilename(cl::Positional,
     59                                           cl::desc("<input bitcode file>"),
     60                                           cl::init("-"),
     61                                           cl::value_desc("filename"));
     62 
     63 static cl::opt<bool> SaveTemps("save-temps", cl::desc("Save temp files"),
     64                                cl::init(false));
     65 
     66 static cl::opt<unsigned>
     67     NumShuffles("num-shuffles",
     68                 cl::desc("Number of times to shuffle and verify use-lists"),
     69                 cl::init(1));
     70 
     71 namespace {
     72 
     73 struct TempFile {
     74   std::string Filename;
     75   FileRemover Remover;
     76   bool init(const std::string &Ext);
     77   bool writeBitcode(const Module &M) const;
     78   bool writeAssembly(const Module &M) const;
     79   std::unique_ptr<Module> readBitcode(LLVMContext &Context) const;
     80   std::unique_ptr<Module> readAssembly(LLVMContext &Context) const;
     81 };
     82 
     83 struct ValueMapping {
     84   DenseMap<const Value *, unsigned> IDs;
     85   std::vector<const Value *> Values;
     86 
     87   /// \brief Construct a value mapping for module.
     88   ///
     89   /// Creates mapping from every value in \c M to an ID.  This mapping includes
     90   /// un-referencable values.
     91   ///
     92   /// Every \a Value that gets serialized in some way should be represented
     93   /// here.  The order needs to be deterministic, but it's unnecessary to match
     94   /// the value-ids in the bitcode writer.
     95   ///
     96   /// All constants that are referenced by other values are included in the
     97   /// mapping, but others -- which wouldn't be serialized -- are not.
     98   ValueMapping(const Module &M);
     99 
    100   /// \brief Map a value.
    101   ///
    102   /// Maps a value.  If it's a constant, maps all of its operands first.
    103   void map(const Value *V);
    104   unsigned lookup(const Value *V) const { return IDs.lookup(V); }
    105 };
    106 
    107 } // end namespace
    108 
    109 bool TempFile::init(const std::string &Ext) {
    110   SmallVector<char, 64> Vector;
    111   DEBUG(dbgs() << " - create-temp-file\n");
    112   if (auto EC = sys::fs::createTemporaryFile("uselistorder", Ext, Vector)) {
    113     errs() << "verify-uselistorder: error: " << EC.message() << "\n";
    114     return true;
    115   }
    116   assert(!Vector.empty());
    117 
    118   Filename.assign(Vector.data(), Vector.data() + Vector.size());
    119   Remover.setFile(Filename, !SaveTemps);
    120   if (SaveTemps)
    121     outs() << " - filename = " << Filename << "\n";
    122   return false;
    123 }
    124 
    125 bool TempFile::writeBitcode(const Module &M) const {
    126   DEBUG(dbgs() << " - write bitcode\n");
    127   std::error_code EC;
    128   raw_fd_ostream OS(Filename, EC, sys::fs::F_None);
    129   if (EC) {
    130     errs() << "verify-uselistorder: error: " << EC.message() << "\n";
    131     return true;
    132   }
    133 
    134   WriteBitcodeToFile(&M, OS, /* ShouldPreserveUseListOrder */ true);
    135   return false;
    136 }
    137 
    138 bool TempFile::writeAssembly(const Module &M) const {
    139   DEBUG(dbgs() << " - write assembly\n");
    140   std::error_code EC;
    141   raw_fd_ostream OS(Filename, EC, sys::fs::F_Text);
    142   if (EC) {
    143     errs() << "verify-uselistorder: error: " << EC.message() << "\n";
    144     return true;
    145   }
    146 
    147   M.print(OS, nullptr, /* ShouldPreserveUseListOrder */ true);
    148   return false;
    149 }
    150 
    151 std::unique_ptr<Module> TempFile::readBitcode(LLVMContext &Context) const {
    152   DEBUG(dbgs() << " - read bitcode\n");
    153   ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOr =
    154       MemoryBuffer::getFile(Filename);
    155   if (!BufferOr) {
    156     errs() << "verify-uselistorder: error: " << BufferOr.getError().message()
    157            << "\n";
    158     return nullptr;
    159   }
    160 
    161   MemoryBuffer *Buffer = BufferOr.get().get();
    162   ErrorOr<std::unique_ptr<Module>> ModuleOr =
    163       parseBitcodeFile(Buffer->getMemBufferRef(), Context);
    164   if (!ModuleOr) {
    165     errs() << "verify-uselistorder: error: " << ModuleOr.getError().message()
    166            << "\n";
    167     return nullptr;
    168   }
    169   return std::move(ModuleOr.get());
    170 }
    171 
    172 std::unique_ptr<Module> TempFile::readAssembly(LLVMContext &Context) const {
    173   DEBUG(dbgs() << " - read assembly\n");
    174   SMDiagnostic Err;
    175   std::unique_ptr<Module> M = parseAssemblyFile(Filename, Err, Context);
    176   if (!M.get())
    177     Err.print("verify-uselistorder", errs());
    178   return M;
    179 }
    180 
    181 ValueMapping::ValueMapping(const Module &M) {
    182   // Every value should be mapped, including things like void instructions and
    183   // basic blocks that are kept out of the ValueEnumerator.
    184   //
    185   // The current mapping order makes it easier to debug the tables.  It happens
    186   // to be similar to the ID mapping when writing ValueEnumerator, but they
    187   // aren't (and needn't be) in sync.
    188 
    189   // Globals.
    190   for (const GlobalVariable &G : M.globals())
    191     map(&G);
    192   for (const GlobalAlias &A : M.aliases())
    193     map(&A);
    194   for (const Function &F : M)
    195     map(&F);
    196 
    197   // Constants used by globals.
    198   for (const GlobalVariable &G : M.globals())
    199     if (G.hasInitializer())
    200       map(G.getInitializer());
    201   for (const GlobalAlias &A : M.aliases())
    202     map(A.getAliasee());
    203   for (const Function &F : M) {
    204     if (F.hasPrefixData())
    205       map(F.getPrefixData());
    206     if (F.hasPrologueData())
    207       map(F.getPrologueData());
    208     if (F.hasPersonalityFn())
    209       map(F.getPersonalityFn());
    210   }
    211 
    212   // Function bodies.
    213   for (const Function &F : M) {
    214     for (const Argument &A : F.args())
    215       map(&A);
    216     for (const BasicBlock &BB : F)
    217       map(&BB);
    218     for (const BasicBlock &BB : F)
    219       for (const Instruction &I : BB)
    220         map(&I);
    221 
    222     // Constants used by instructions.
    223     for (const BasicBlock &BB : F)
    224       for (const Instruction &I : BB)
    225         for (const Value *Op : I.operands())
    226           if ((isa<Constant>(Op) && !isa<GlobalValue>(*Op)) ||
    227               isa<InlineAsm>(Op))
    228             map(Op);
    229   }
    230 }
    231 
    232 void ValueMapping::map(const Value *V) {
    233   if (IDs.lookup(V))
    234     return;
    235 
    236   if (auto *C = dyn_cast<Constant>(V))
    237     if (!isa<GlobalValue>(C))
    238       for (const Value *Op : C->operands())
    239         map(Op);
    240 
    241   Values.push_back(V);
    242   IDs[V] = Values.size();
    243 }
    244 
    245 #ifndef NDEBUG
    246 static void dumpMapping(const ValueMapping &VM) {
    247   dbgs() << "value-mapping (size = " << VM.Values.size() << "):\n";
    248   for (unsigned I = 0, E = VM.Values.size(); I != E; ++I) {
    249     dbgs() << " - id = " << I << ", value = ";
    250     VM.Values[I]->dump();
    251   }
    252 }
    253 
    254 static void debugValue(const ValueMapping &M, unsigned I, StringRef Desc) {
    255   const Value *V = M.Values[I];
    256   dbgs() << " - " << Desc << " value = ";
    257   V->dump();
    258   for (const Use &U : V->uses()) {
    259     dbgs() << "   => use: op = " << U.getOperandNo()
    260            << ", user-id = " << M.IDs.lookup(U.getUser()) << ", user = ";
    261     U.getUser()->dump();
    262   }
    263 }
    264 
    265 static void debugUserMismatch(const ValueMapping &L, const ValueMapping &R,
    266                               unsigned I) {
    267   dbgs() << " - fail: user mismatch: ID = " << I << "\n";
    268   debugValue(L, I, "LHS");
    269   debugValue(R, I, "RHS");
    270 
    271   dbgs() << "\nlhs-";
    272   dumpMapping(L);
    273   dbgs() << "\nrhs-";
    274   dumpMapping(R);
    275 }
    276 
    277 static void debugSizeMismatch(const ValueMapping &L, const ValueMapping &R) {
    278   dbgs() << " - fail: map size: " << L.Values.size()
    279          << " != " << R.Values.size() << "\n";
    280   dbgs() << "\nlhs-";
    281   dumpMapping(L);
    282   dbgs() << "\nrhs-";
    283   dumpMapping(R);
    284 }
    285 #endif
    286 
    287 static bool matches(const ValueMapping &LM, const ValueMapping &RM) {
    288   DEBUG(dbgs() << "compare value maps\n");
    289   if (LM.Values.size() != RM.Values.size()) {
    290     DEBUG(debugSizeMismatch(LM, RM));
    291     return false;
    292   }
    293 
    294   // This mapping doesn't include dangling constant users, since those don't
    295   // get serialized.  However, checking if users are constant and calling
    296   // isConstantUsed() on every one is very expensive.  Instead, just check if
    297   // the user is mapped.
    298   auto skipUnmappedUsers =
    299       [&](Value::const_use_iterator &U, Value::const_use_iterator E,
    300           const ValueMapping &M) {
    301     while (U != E && !M.lookup(U->getUser()))
    302       ++U;
    303   };
    304 
    305   // Iterate through all values, and check that both mappings have the same
    306   // users.
    307   for (unsigned I = 0, E = LM.Values.size(); I != E; ++I) {
    308     const Value *L = LM.Values[I];
    309     const Value *R = RM.Values[I];
    310     auto LU = L->use_begin(), LE = L->use_end();
    311     auto RU = R->use_begin(), RE = R->use_end();
    312     skipUnmappedUsers(LU, LE, LM);
    313     skipUnmappedUsers(RU, RE, RM);
    314 
    315     while (LU != LE) {
    316       if (RU == RE) {
    317         DEBUG(debugUserMismatch(LM, RM, I));
    318         return false;
    319       }
    320       if (LM.lookup(LU->getUser()) != RM.lookup(RU->getUser())) {
    321         DEBUG(debugUserMismatch(LM, RM, I));
    322         return false;
    323       }
    324       if (LU->getOperandNo() != RU->getOperandNo()) {
    325         DEBUG(debugUserMismatch(LM, RM, I));
    326         return false;
    327       }
    328       skipUnmappedUsers(++LU, LE, LM);
    329       skipUnmappedUsers(++RU, RE, RM);
    330     }
    331     if (RU != RE) {
    332       DEBUG(debugUserMismatch(LM, RM, I));
    333       return false;
    334     }
    335   }
    336 
    337   return true;
    338 }
    339 
    340 static void verifyAfterRoundTrip(const Module &M,
    341                                  std::unique_ptr<Module> OtherM) {
    342   if (!OtherM)
    343     report_fatal_error("parsing failed");
    344   if (verifyModule(*OtherM, &errs()))
    345     report_fatal_error("verification failed");
    346   if (!matches(ValueMapping(M), ValueMapping(*OtherM)))
    347     report_fatal_error("use-list order changed");
    348 }
    349 
    350 static void verifyBitcodeUseListOrder(const Module &M) {
    351   TempFile F;
    352   if (F.init("bc"))
    353     report_fatal_error("failed to initialize bitcode file");
    354 
    355   if (F.writeBitcode(M))
    356     report_fatal_error("failed to write bitcode");
    357 
    358   LLVMContext Context;
    359   verifyAfterRoundTrip(M, F.readBitcode(Context));
    360 }
    361 
    362 static void verifyAssemblyUseListOrder(const Module &M) {
    363   TempFile F;
    364   if (F.init("ll"))
    365     report_fatal_error("failed to initialize assembly file");
    366 
    367   if (F.writeAssembly(M))
    368     report_fatal_error("failed to write assembly");
    369 
    370   LLVMContext Context;
    371   verifyAfterRoundTrip(M, F.readAssembly(Context));
    372 }
    373 
    374 static void verifyUseListOrder(const Module &M) {
    375   outs() << "verify bitcode\n";
    376   verifyBitcodeUseListOrder(M);
    377   outs() << "verify assembly\n";
    378   verifyAssemblyUseListOrder(M);
    379 }
    380 
    381 static void shuffleValueUseLists(Value *V, std::minstd_rand0 &Gen,
    382                                  DenseSet<Value *> &Seen) {
    383   if (!Seen.insert(V).second)
    384     return;
    385 
    386   if (auto *C = dyn_cast<Constant>(V))
    387     if (!isa<GlobalValue>(C))
    388       for (Value *Op : C->operands())
    389         shuffleValueUseLists(Op, Gen, Seen);
    390 
    391   if (V->use_empty() || std::next(V->use_begin()) == V->use_end())
    392     // Nothing to shuffle for 0 or 1 users.
    393     return;
    394 
    395   // Generate random numbers between 10 and 99, which will line up nicely in
    396   // debug output.  We're not worried about collisons here.
    397   DEBUG(dbgs() << "V = "; V->dump());
    398   std::uniform_int_distribution<short> Dist(10, 99);
    399   SmallDenseMap<const Use *, short, 16> Order;
    400   auto compareUses =
    401       [&Order](const Use &L, const Use &R) { return Order[&L] < Order[&R]; };
    402   do {
    403     for (const Use &U : V->uses()) {
    404       auto I = Dist(Gen);
    405       Order[&U] = I;
    406       DEBUG(dbgs() << " - order: " << I << ", op = " << U.getOperandNo()
    407                    << ", U = ";
    408             U.getUser()->dump());
    409     }
    410   } while (std::is_sorted(V->use_begin(), V->use_end(), compareUses));
    411 
    412   DEBUG(dbgs() << " => shuffle\n");
    413   V->sortUseList(compareUses);
    414 
    415   DEBUG({
    416     for (const Use &U : V->uses()) {
    417       dbgs() << " - order: " << Order.lookup(&U)
    418              << ", op = " << U.getOperandNo() << ", U = ";
    419       U.getUser()->dump();
    420     }
    421   });
    422 }
    423 
    424 static void reverseValueUseLists(Value *V, DenseSet<Value *> &Seen) {
    425   if (!Seen.insert(V).second)
    426     return;
    427 
    428   if (auto *C = dyn_cast<Constant>(V))
    429     if (!isa<GlobalValue>(C))
    430       for (Value *Op : C->operands())
    431         reverseValueUseLists(Op, Seen);
    432 
    433   if (V->use_empty() || std::next(V->use_begin()) == V->use_end())
    434     // Nothing to shuffle for 0 or 1 users.
    435     return;
    436 
    437   DEBUG({
    438     dbgs() << "V = ";
    439     V->dump();
    440     for (const Use &U : V->uses()) {
    441       dbgs() << " - order: op = " << U.getOperandNo() << ", U = ";
    442       U.getUser()->dump();
    443     }
    444     dbgs() << " => reverse\n";
    445   });
    446 
    447   V->reverseUseList();
    448 
    449   DEBUG({
    450     for (const Use &U : V->uses()) {
    451       dbgs() << " - order: op = " << U.getOperandNo() << ", U = ";
    452       U.getUser()->dump();
    453     }
    454   });
    455 }
    456 
    457 template <class Changer>
    458 static void changeUseLists(Module &M, Changer changeValueUseList) {
    459   // Visit every value that would be serialized to an IR file.
    460   //
    461   // Globals.
    462   for (GlobalVariable &G : M.globals())
    463     changeValueUseList(&G);
    464   for (GlobalAlias &A : M.aliases())
    465     changeValueUseList(&A);
    466   for (Function &F : M)
    467     changeValueUseList(&F);
    468 
    469   // Constants used by globals.
    470   for (GlobalVariable &G : M.globals())
    471     if (G.hasInitializer())
    472       changeValueUseList(G.getInitializer());
    473   for (GlobalAlias &A : M.aliases())
    474     changeValueUseList(A.getAliasee());
    475   for (Function &F : M) {
    476     if (F.hasPrefixData())
    477       changeValueUseList(F.getPrefixData());
    478     if (F.hasPrologueData())
    479       changeValueUseList(F.getPrologueData());
    480     if (F.hasPersonalityFn())
    481       changeValueUseList(F.getPersonalityFn());
    482   }
    483 
    484   // Function bodies.
    485   for (Function &F : M) {
    486     for (Argument &A : F.args())
    487       changeValueUseList(&A);
    488     for (BasicBlock &BB : F)
    489       changeValueUseList(&BB);
    490     for (BasicBlock &BB : F)
    491       for (Instruction &I : BB)
    492         changeValueUseList(&I);
    493 
    494     // Constants used by instructions.
    495     for (BasicBlock &BB : F)
    496       for (Instruction &I : BB)
    497         for (Value *Op : I.operands())
    498           if ((isa<Constant>(Op) && !isa<GlobalValue>(*Op)) ||
    499               isa<InlineAsm>(Op))
    500             changeValueUseList(Op);
    501   }
    502 
    503   if (verifyModule(M, &errs()))
    504     report_fatal_error("verification failed");
    505 }
    506 
    507 static void shuffleUseLists(Module &M, unsigned SeedOffset) {
    508   std::minstd_rand0 Gen(std::minstd_rand0::default_seed + SeedOffset);
    509   DenseSet<Value *> Seen;
    510   changeUseLists(M, [&](Value *V) { shuffleValueUseLists(V, Gen, Seen); });
    511   DEBUG(dbgs() << "\n");
    512 }
    513 
    514 static void reverseUseLists(Module &M) {
    515   DenseSet<Value *> Seen;
    516   changeUseLists(M, [&](Value *V) { reverseValueUseLists(V, Seen); });
    517   DEBUG(dbgs() << "\n");
    518 }
    519 
    520 int main(int argc, char **argv) {
    521   sys::PrintStackTraceOnErrorSignal();
    522   llvm::PrettyStackTraceProgram X(argc, argv);
    523 
    524   // Enable debug stream buffering.
    525   EnableDebugBuffering = true;
    526 
    527   llvm_shutdown_obj Y; // Call llvm_shutdown() on exit.
    528   LLVMContext &Context = getGlobalContext();
    529 
    530   cl::ParseCommandLineOptions(argc, argv,
    531                               "llvm tool to verify use-list order\n");
    532 
    533   SMDiagnostic Err;
    534 
    535   // Load the input module...
    536   std::unique_ptr<Module> M = parseIRFile(InputFilename, Err, Context);
    537 
    538   if (!M.get()) {
    539     Err.print(argv[0], errs());
    540     return 1;
    541   }
    542   if (verifyModule(*M, &errs())) {
    543     errs() << argv[0] << ": " << InputFilename
    544            << ": error: input module is broken!\n";
    545     return 1;
    546   }
    547 
    548   // Verify the use lists now and after reversing them.
    549   outs() << "*** verify-uselistorder ***\n";
    550   verifyUseListOrder(*M);
    551   outs() << "reverse\n";
    552   reverseUseLists(*M);
    553   verifyUseListOrder(*M);
    554 
    555   for (unsigned I = 0, E = NumShuffles; I != E; ++I) {
    556     outs() << "\n";
    557 
    558     // Shuffle with a different (deterministic) seed each time.
    559     outs() << "shuffle (" << I + 1 << " of " << E << ")\n";
    560     shuffleUseLists(*M, I);
    561 
    562     // Verify again before and after reversing.
    563     verifyUseListOrder(*M);
    564     outs() << "reverse\n";
    565     reverseUseLists(*M);
    566     verifyUseListOrder(*M);
    567   }
    568 
    569   return 0;
    570 }
    571