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      1 //===- GCOVProfiling.cpp - Insert edge counters for gcov profiling --------===//
      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 pass implements GCOV-style profiling. When this pass is run it emits
     11 // "gcno" files next to the existing source, and instruments the code that runs
     12 // to records the edges between blocks that run and emit a complementary "gcda"
     13 // file on exit.
     14 //
     15 //===----------------------------------------------------------------------===//
     16 
     17 #include "llvm/Transforms/Instrumentation.h"
     18 #include "llvm/ADT/DenseMap.h"
     19 #include "llvm/ADT/Hashing.h"
     20 #include "llvm/ADT/STLExtras.h"
     21 #include "llvm/ADT/Statistic.h"
     22 #include "llvm/ADT/StringExtras.h"
     23 #include "llvm/ADT/StringMap.h"
     24 #include "llvm/ADT/UniqueVector.h"
     25 #include "llvm/IR/DebugInfo.h"
     26 #include "llvm/IR/DebugLoc.h"
     27 #include "llvm/IR/IRBuilder.h"
     28 #include "llvm/IR/InstIterator.h"
     29 #include "llvm/IR/Instructions.h"
     30 #include "llvm/IR/IntrinsicInst.h"
     31 #include "llvm/IR/Module.h"
     32 #include "llvm/Pass.h"
     33 #include "llvm/Support/CommandLine.h"
     34 #include "llvm/Support/Debug.h"
     35 #include "llvm/Support/FileSystem.h"
     36 #include "llvm/Support/Path.h"
     37 #include "llvm/Support/raw_ostream.h"
     38 #include "llvm/Transforms/Utils/ModuleUtils.h"
     39 #include <algorithm>
     40 #include <memory>
     41 #include <string>
     42 #include <utility>
     43 using namespace llvm;
     44 
     45 #define DEBUG_TYPE "insert-gcov-profiling"
     46 
     47 static cl::opt<std::string>
     48 DefaultGCOVVersion("default-gcov-version", cl::init("402*"), cl::Hidden,
     49                    cl::ValueRequired);
     50 
     51 GCOVOptions GCOVOptions::getDefault() {
     52   GCOVOptions Options;
     53   Options.EmitNotes = true;
     54   Options.EmitData = true;
     55   Options.UseCfgChecksum = false;
     56   Options.NoRedZone = false;
     57   Options.FunctionNamesInData = true;
     58 
     59   if (DefaultGCOVVersion.size() != 4) {
     60     llvm::report_fatal_error(std::string("Invalid -default-gcov-version: ") +
     61                              DefaultGCOVVersion);
     62   }
     63   memcpy(Options.Version, DefaultGCOVVersion.c_str(), 4);
     64   return Options;
     65 }
     66 
     67 namespace {
     68   class GCOVFunction;
     69 
     70   class GCOVProfiler : public ModulePass {
     71   public:
     72     static char ID;
     73     GCOVProfiler() : ModulePass(ID), Options(GCOVOptions::getDefault()) {
     74       init();
     75     }
     76     GCOVProfiler(const GCOVOptions &Options) : ModulePass(ID), Options(Options){
     77       assert((Options.EmitNotes || Options.EmitData) &&
     78              "GCOVProfiler asked to do nothing?");
     79       init();
     80     }
     81     const char *getPassName() const override {
     82       return "GCOV Profiler";
     83     }
     84 
     85   private:
     86     void init() {
     87       ReversedVersion[0] = Options.Version[3];
     88       ReversedVersion[1] = Options.Version[2];
     89       ReversedVersion[2] = Options.Version[1];
     90       ReversedVersion[3] = Options.Version[0];
     91       ReversedVersion[4] = '\0';
     92       initializeGCOVProfilerPass(*PassRegistry::getPassRegistry());
     93     }
     94     bool runOnModule(Module &M) override;
     95 
     96     // Create the .gcno files for the Module based on DebugInfo.
     97     void emitProfileNotes();
     98 
     99     // Modify the program to track transitions along edges and call into the
    100     // profiling runtime to emit .gcda files when run.
    101     bool emitProfileArcs();
    102 
    103     // Get pointers to the functions in the runtime library.
    104     Constant *getStartFileFunc();
    105     Constant *getIncrementIndirectCounterFunc();
    106     Constant *getEmitFunctionFunc();
    107     Constant *getEmitArcsFunc();
    108     Constant *getSummaryInfoFunc();
    109     Constant *getDeleteWriteoutFunctionListFunc();
    110     Constant *getDeleteFlushFunctionListFunc();
    111     Constant *getEndFileFunc();
    112 
    113     // Create or retrieve an i32 state value that is used to represent the
    114     // pred block number for certain non-trivial edges.
    115     GlobalVariable *getEdgeStateValue();
    116 
    117     // Produce a table of pointers to counters, by predecessor and successor
    118     // block number.
    119     GlobalVariable *buildEdgeLookupTable(Function *F,
    120                                          GlobalVariable *Counter,
    121                                          const UniqueVector<BasicBlock *>&Preds,
    122                                          const UniqueVector<BasicBlock*>&Succs);
    123 
    124     // Add the function to write out all our counters to the global destructor
    125     // list.
    126     Function *insertCounterWriteout(ArrayRef<std::pair<GlobalVariable*,
    127                                                        MDNode*> >);
    128     Function *insertFlush(ArrayRef<std::pair<GlobalVariable*, MDNode*> >);
    129     void insertIndirectCounterIncrement();
    130 
    131     std::string mangleName(DICompileUnit CU, const char *NewStem);
    132 
    133     GCOVOptions Options;
    134 
    135     // Reversed, NUL-terminated copy of Options.Version.
    136     char ReversedVersion[5];
    137     // Checksum, produced by hash of EdgeDestinations
    138     SmallVector<uint32_t, 4> FileChecksums;
    139 
    140     Module *M;
    141     LLVMContext *Ctx;
    142     SmallVector<std::unique_ptr<GCOVFunction>, 16> Funcs;
    143   };
    144 }
    145 
    146 char GCOVProfiler::ID = 0;
    147 INITIALIZE_PASS(GCOVProfiler, "insert-gcov-profiling",
    148                 "Insert instrumentation for GCOV profiling", false, false)
    149 
    150 ModulePass *llvm::createGCOVProfilerPass(const GCOVOptions &Options) {
    151   return new GCOVProfiler(Options);
    152 }
    153 
    154 static StringRef getFunctionName(DISubprogram SP) {
    155   if (!SP.getLinkageName().empty())
    156     return SP.getLinkageName();
    157   return SP.getName();
    158 }
    159 
    160 namespace {
    161   class GCOVRecord {
    162    protected:
    163     static const char *const LinesTag;
    164     static const char *const FunctionTag;
    165     static const char *const BlockTag;
    166     static const char *const EdgeTag;
    167 
    168     GCOVRecord() {}
    169 
    170     void writeBytes(const char *Bytes, int Size) {
    171       os->write(Bytes, Size);
    172     }
    173 
    174     void write(uint32_t i) {
    175       writeBytes(reinterpret_cast<char*>(&i), 4);
    176     }
    177 
    178     // Returns the length measured in 4-byte blocks that will be used to
    179     // represent this string in a GCOV file
    180     static unsigned lengthOfGCOVString(StringRef s) {
    181       // A GCOV string is a length, followed by a NUL, then between 0 and 3 NULs
    182       // padding out to the next 4-byte word. The length is measured in 4-byte
    183       // words including padding, not bytes of actual string.
    184       return (s.size() / 4) + 1;
    185     }
    186 
    187     void writeGCOVString(StringRef s) {
    188       uint32_t Len = lengthOfGCOVString(s);
    189       write(Len);
    190       writeBytes(s.data(), s.size());
    191 
    192       // Write 1 to 4 bytes of NUL padding.
    193       assert((unsigned)(4 - (s.size() % 4)) > 0);
    194       assert((unsigned)(4 - (s.size() % 4)) <= 4);
    195       writeBytes("\0\0\0\0", 4 - (s.size() % 4));
    196     }
    197 
    198     raw_ostream *os;
    199   };
    200   const char *const GCOVRecord::LinesTag = "\0\0\x45\x01";
    201   const char *const GCOVRecord::FunctionTag = "\0\0\0\1";
    202   const char *const GCOVRecord::BlockTag = "\0\0\x41\x01";
    203   const char *const GCOVRecord::EdgeTag = "\0\0\x43\x01";
    204 
    205   class GCOVFunction;
    206   class GCOVBlock;
    207 
    208   // Constructed only by requesting it from a GCOVBlock, this object stores a
    209   // list of line numbers and a single filename, representing lines that belong
    210   // to the block.
    211   class GCOVLines : public GCOVRecord {
    212    public:
    213     void addLine(uint32_t Line) {
    214       assert(Line != 0 && "Line zero is not a valid real line number.");
    215       Lines.push_back(Line);
    216     }
    217 
    218     uint32_t length() const {
    219       // Here 2 = 1 for string length + 1 for '0' id#.
    220       return lengthOfGCOVString(Filename) + 2 + Lines.size();
    221     }
    222 
    223     void writeOut() {
    224       write(0);
    225       writeGCOVString(Filename);
    226       for (int i = 0, e = Lines.size(); i != e; ++i)
    227         write(Lines[i]);
    228     }
    229 
    230     GCOVLines(StringRef F, raw_ostream *os)
    231       : Filename(F) {
    232       this->os = os;
    233     }
    234 
    235    private:
    236     StringRef Filename;
    237     SmallVector<uint32_t, 32> Lines;
    238   };
    239 
    240 
    241   // Represent a basic block in GCOV. Each block has a unique number in the
    242   // function, number of lines belonging to each block, and a set of edges to
    243   // other blocks.
    244   class GCOVBlock : public GCOVRecord {
    245    public:
    246     GCOVLines &getFile(StringRef Filename) {
    247       GCOVLines *&Lines = LinesByFile[Filename];
    248       if (!Lines) {
    249         Lines = new GCOVLines(Filename, os);
    250       }
    251       return *Lines;
    252     }
    253 
    254     void addEdge(GCOVBlock &Successor) {
    255       OutEdges.push_back(&Successor);
    256     }
    257 
    258     void writeOut() {
    259       uint32_t Len = 3;
    260       SmallVector<StringMapEntry<GCOVLines *> *, 32> SortedLinesByFile;
    261       for (StringMap<GCOVLines *>::iterator I = LinesByFile.begin(),
    262                E = LinesByFile.end(); I != E; ++I) {
    263         Len += I->second->length();
    264         SortedLinesByFile.push_back(&*I);
    265       }
    266 
    267       writeBytes(LinesTag, 4);
    268       write(Len);
    269       write(Number);
    270 
    271       std::sort(SortedLinesByFile.begin(), SortedLinesByFile.end(),
    272                 [](StringMapEntry<GCOVLines *> *LHS,
    273                    StringMapEntry<GCOVLines *> *RHS) {
    274         return LHS->getKey() < RHS->getKey();
    275       });
    276       for (SmallVectorImpl<StringMapEntry<GCOVLines *> *>::iterator
    277                I = SortedLinesByFile.begin(), E = SortedLinesByFile.end();
    278            I != E; ++I)
    279         (*I)->getValue()->writeOut();
    280       write(0);
    281       write(0);
    282     }
    283 
    284     ~GCOVBlock() {
    285       DeleteContainerSeconds(LinesByFile);
    286     }
    287 
    288    private:
    289     friend class GCOVFunction;
    290 
    291     GCOVBlock(uint32_t Number, raw_ostream *os)
    292         : Number(Number) {
    293       this->os = os;
    294     }
    295 
    296     uint32_t Number;
    297     StringMap<GCOVLines *> LinesByFile;
    298     SmallVector<GCOVBlock *, 4> OutEdges;
    299   };
    300 
    301   // A function has a unique identifier, a checksum (we leave as zero) and a
    302   // set of blocks and a map of edges between blocks. This is the only GCOV
    303   // object users can construct, the blocks and lines will be rooted here.
    304   class GCOVFunction : public GCOVRecord {
    305    public:
    306     GCOVFunction(DISubprogram SP, raw_ostream *os, uint32_t Ident,
    307                  bool UseCfgChecksum) :
    308         SP(SP), Ident(Ident), UseCfgChecksum(UseCfgChecksum), CfgChecksum(0) {
    309       this->os = os;
    310 
    311       Function *F = SP.getFunction();
    312       DEBUG(dbgs() << "Function: " << getFunctionName(SP) << "\n");
    313       uint32_t i = 0;
    314       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
    315         Blocks[BB] = new GCOVBlock(i++, os);
    316       }
    317       ReturnBlock = new GCOVBlock(i++, os);
    318 
    319       std::string FunctionNameAndLine;
    320       raw_string_ostream FNLOS(FunctionNameAndLine);
    321       FNLOS << getFunctionName(SP) << SP.getLineNumber();
    322       FNLOS.flush();
    323       FuncChecksum = hash_value(FunctionNameAndLine);
    324     }
    325 
    326     ~GCOVFunction() {
    327       DeleteContainerSeconds(Blocks);
    328       delete ReturnBlock;
    329     }
    330 
    331     GCOVBlock &getBlock(BasicBlock *BB) {
    332       return *Blocks[BB];
    333     }
    334 
    335     GCOVBlock &getReturnBlock() {
    336       return *ReturnBlock;
    337     }
    338 
    339     std::string getEdgeDestinations() {
    340       std::string EdgeDestinations;
    341       raw_string_ostream EDOS(EdgeDestinations);
    342       Function *F = Blocks.begin()->first->getParent();
    343       for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
    344         GCOVBlock &Block = *Blocks[I];
    345         for (int i = 0, e = Block.OutEdges.size(); i != e; ++i)
    346           EDOS << Block.OutEdges[i]->Number;
    347       }
    348       return EdgeDestinations;
    349     }
    350 
    351     uint32_t getFuncChecksum() {
    352       return FuncChecksum;
    353     }
    354 
    355     void setCfgChecksum(uint32_t Checksum) {
    356       CfgChecksum = Checksum;
    357     }
    358 
    359     void writeOut() {
    360       writeBytes(FunctionTag, 4);
    361       uint32_t BlockLen = 1 + 1 + 1 + lengthOfGCOVString(getFunctionName(SP)) +
    362           1 + lengthOfGCOVString(SP.getFilename()) + 1;
    363       if (UseCfgChecksum)
    364         ++BlockLen;
    365       write(BlockLen);
    366       write(Ident);
    367       write(FuncChecksum);
    368       if (UseCfgChecksum)
    369         write(CfgChecksum);
    370       writeGCOVString(getFunctionName(SP));
    371       writeGCOVString(SP.getFilename());
    372       write(SP.getLineNumber());
    373 
    374       // Emit count of blocks.
    375       writeBytes(BlockTag, 4);
    376       write(Blocks.size() + 1);
    377       for (int i = 0, e = Blocks.size() + 1; i != e; ++i) {
    378         write(0);  // No flags on our blocks.
    379       }
    380       DEBUG(dbgs() << Blocks.size() << " blocks.\n");
    381 
    382       // Emit edges between blocks.
    383       if (Blocks.empty()) return;
    384       Function *F = Blocks.begin()->first->getParent();
    385       for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
    386         GCOVBlock &Block = *Blocks[I];
    387         if (Block.OutEdges.empty()) continue;
    388 
    389         writeBytes(EdgeTag, 4);
    390         write(Block.OutEdges.size() * 2 + 1);
    391         write(Block.Number);
    392         for (int i = 0, e = Block.OutEdges.size(); i != e; ++i) {
    393           DEBUG(dbgs() << Block.Number << " -> " << Block.OutEdges[i]->Number
    394                        << "\n");
    395           write(Block.OutEdges[i]->Number);
    396           write(0);  // no flags
    397         }
    398       }
    399 
    400       // Emit lines for each block.
    401       for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
    402         Blocks[I]->writeOut();
    403       }
    404     }
    405 
    406    private:
    407     DISubprogram SP;
    408     uint32_t Ident;
    409     uint32_t FuncChecksum;
    410     bool UseCfgChecksum;
    411     uint32_t CfgChecksum;
    412     DenseMap<BasicBlock *, GCOVBlock *> Blocks;
    413     GCOVBlock *ReturnBlock;
    414   };
    415 }
    416 
    417 std::string GCOVProfiler::mangleName(DICompileUnit CU, const char *NewStem) {
    418   if (NamedMDNode *GCov = M->getNamedMetadata("llvm.gcov")) {
    419     for (int i = 0, e = GCov->getNumOperands(); i != e; ++i) {
    420       MDNode *N = GCov->getOperand(i);
    421       if (N->getNumOperands() != 2) continue;
    422       MDString *GCovFile = dyn_cast<MDString>(N->getOperand(0));
    423       MDNode *CompileUnit = dyn_cast<MDNode>(N->getOperand(1));
    424       if (!GCovFile || !CompileUnit) continue;
    425       if (CompileUnit == CU) {
    426         SmallString<128> Filename = GCovFile->getString();
    427         sys::path::replace_extension(Filename, NewStem);
    428         return Filename.str();
    429       }
    430     }
    431   }
    432 
    433   SmallString<128> Filename = CU.getFilename();
    434   sys::path::replace_extension(Filename, NewStem);
    435   StringRef FName = sys::path::filename(Filename);
    436   SmallString<128> CurPath;
    437   if (sys::fs::current_path(CurPath)) return FName;
    438   sys::path::append(CurPath, FName.str());
    439   return CurPath.str();
    440 }
    441 
    442 bool GCOVProfiler::runOnModule(Module &M) {
    443   this->M = &M;
    444   Ctx = &M.getContext();
    445 
    446   if (Options.EmitNotes) emitProfileNotes();
    447   if (Options.EmitData) return emitProfileArcs();
    448   return false;
    449 }
    450 
    451 static bool functionHasLines(Function *F) {
    452   // Check whether this function actually has any source lines. Not only
    453   // do these waste space, they also can crash gcov.
    454   for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
    455     for (BasicBlock::iterator I = BB->begin(), IE = BB->end();
    456          I != IE; ++I) {
    457       // Debug intrinsic locations correspond to the location of the
    458       // declaration, not necessarily any statements or expressions.
    459       if (isa<DbgInfoIntrinsic>(I)) continue;
    460 
    461       const DebugLoc &Loc = I->getDebugLoc();
    462       if (Loc.isUnknown()) continue;
    463 
    464       // Artificial lines such as calls to the global constructors.
    465       if (Loc.getLine() == 0) continue;
    466 
    467       return true;
    468     }
    469   }
    470   return false;
    471 }
    472 
    473 void GCOVProfiler::emitProfileNotes() {
    474   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
    475   if (!CU_Nodes) return;
    476 
    477   for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
    478     // Each compile unit gets its own .gcno file. This means that whether we run
    479     // this pass over the original .o's as they're produced, or run it after
    480     // LTO, we'll generate the same .gcno files.
    481 
    482     DICompileUnit CU(CU_Nodes->getOperand(i));
    483     std::string ErrorInfo;
    484     raw_fd_ostream out(mangleName(CU, "gcno").c_str(), ErrorInfo,
    485                        sys::fs::F_None);
    486     std::string EdgeDestinations;
    487 
    488     DIArray SPs = CU.getSubprograms();
    489     for (unsigned i = 0, e = SPs.getNumElements(); i != e; ++i) {
    490       DISubprogram SP(SPs.getElement(i));
    491       assert((!SP || SP.isSubprogram()) &&
    492         "A MDNode in subprograms of a CU should be null or a DISubprogram.");
    493       if (!SP)
    494         continue;
    495 
    496       Function *F = SP.getFunction();
    497       if (!F) continue;
    498       if (!functionHasLines(F)) continue;
    499 
    500       // gcov expects every function to start with an entry block that has a
    501       // single successor, so split the entry block to make sure of that.
    502       BasicBlock &EntryBlock = F->getEntryBlock();
    503       BasicBlock::iterator It = EntryBlock.begin();
    504       while (isa<AllocaInst>(*It) || isa<DbgInfoIntrinsic>(*It))
    505         ++It;
    506       EntryBlock.splitBasicBlock(It);
    507 
    508       Funcs.push_back(
    509           make_unique<GCOVFunction>(SP, &out, i, Options.UseCfgChecksum));
    510       GCOVFunction &Func = *Funcs.back();
    511 
    512       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
    513         GCOVBlock &Block = Func.getBlock(BB);
    514         TerminatorInst *TI = BB->getTerminator();
    515         if (int successors = TI->getNumSuccessors()) {
    516           for (int i = 0; i != successors; ++i) {
    517             Block.addEdge(Func.getBlock(TI->getSuccessor(i)));
    518           }
    519         } else if (isa<ReturnInst>(TI)) {
    520           Block.addEdge(Func.getReturnBlock());
    521         }
    522 
    523         uint32_t Line = 0;
    524         for (BasicBlock::iterator I = BB->begin(), IE = BB->end();
    525              I != IE; ++I) {
    526           // Debug intrinsic locations correspond to the location of the
    527           // declaration, not necessarily any statements or expressions.
    528           if (isa<DbgInfoIntrinsic>(I)) continue;
    529 
    530           const DebugLoc &Loc = I->getDebugLoc();
    531           if (Loc.isUnknown()) continue;
    532 
    533           // Artificial lines such as calls to the global constructors.
    534           if (Loc.getLine() == 0) continue;
    535 
    536           if (Line == Loc.getLine()) continue;
    537           Line = Loc.getLine();
    538           if (SP != getDISubprogram(Loc.getScope(*Ctx))) continue;
    539 
    540           GCOVLines &Lines = Block.getFile(SP.getFilename());
    541           Lines.addLine(Loc.getLine());
    542         }
    543       }
    544       EdgeDestinations += Func.getEdgeDestinations();
    545     }
    546 
    547     FileChecksums.push_back(hash_value(EdgeDestinations));
    548     out.write("oncg", 4);
    549     out.write(ReversedVersion, 4);
    550     out.write(reinterpret_cast<char*>(&FileChecksums.back()), 4);
    551 
    552     for (auto &Func : Funcs) {
    553       Func->setCfgChecksum(FileChecksums.back());
    554       Func->writeOut();
    555     }
    556 
    557     out.write("\0\0\0\0\0\0\0\0", 8);  // EOF
    558     out.close();
    559   }
    560 }
    561 
    562 bool GCOVProfiler::emitProfileArcs() {
    563   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
    564   if (!CU_Nodes) return false;
    565 
    566   bool Result = false;
    567   bool InsertIndCounterIncrCode = false;
    568   for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
    569     DICompileUnit CU(CU_Nodes->getOperand(i));
    570     DIArray SPs = CU.getSubprograms();
    571     SmallVector<std::pair<GlobalVariable *, MDNode *>, 8> CountersBySP;
    572     for (unsigned i = 0, e = SPs.getNumElements(); i != e; ++i) {
    573       DISubprogram SP(SPs.getElement(i));
    574       assert((!SP || SP.isSubprogram()) &&
    575         "A MDNode in subprograms of a CU should be null or a DISubprogram.");
    576       if (!SP)
    577         continue;
    578       Function *F = SP.getFunction();
    579       if (!F) continue;
    580       if (!functionHasLines(F)) continue;
    581       if (!Result) Result = true;
    582       unsigned Edges = 0;
    583       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
    584         TerminatorInst *TI = BB->getTerminator();
    585         if (isa<ReturnInst>(TI))
    586           ++Edges;
    587         else
    588           Edges += TI->getNumSuccessors();
    589       }
    590 
    591       ArrayType *CounterTy =
    592         ArrayType::get(Type::getInt64Ty(*Ctx), Edges);
    593       GlobalVariable *Counters =
    594         new GlobalVariable(*M, CounterTy, false,
    595                            GlobalValue::InternalLinkage,
    596                            Constant::getNullValue(CounterTy),
    597                            "__llvm_gcov_ctr");
    598       CountersBySP.push_back(std::make_pair(Counters, (MDNode*)SP));
    599 
    600       UniqueVector<BasicBlock *> ComplexEdgePreds;
    601       UniqueVector<BasicBlock *> ComplexEdgeSuccs;
    602 
    603       unsigned Edge = 0;
    604       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
    605         TerminatorInst *TI = BB->getTerminator();
    606         int Successors = isa<ReturnInst>(TI) ? 1 : TI->getNumSuccessors();
    607         if (Successors) {
    608           if (Successors == 1) {
    609             IRBuilder<> Builder(BB->getFirstInsertionPt());
    610             Value *Counter = Builder.CreateConstInBoundsGEP2_64(Counters, 0,
    611                                                                 Edge);
    612             Value *Count = Builder.CreateLoad(Counter);
    613             Count = Builder.CreateAdd(Count, Builder.getInt64(1));
    614             Builder.CreateStore(Count, Counter);
    615           } else if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
    616             IRBuilder<> Builder(BI);
    617             Value *Sel = Builder.CreateSelect(BI->getCondition(),
    618                                               Builder.getInt64(Edge),
    619                                               Builder.getInt64(Edge + 1));
    620             SmallVector<Value *, 2> Idx;
    621             Idx.push_back(Builder.getInt64(0));
    622             Idx.push_back(Sel);
    623             Value *Counter = Builder.CreateInBoundsGEP(Counters, Idx);
    624             Value *Count = Builder.CreateLoad(Counter);
    625             Count = Builder.CreateAdd(Count, Builder.getInt64(1));
    626             Builder.CreateStore(Count, Counter);
    627           } else {
    628             ComplexEdgePreds.insert(BB);
    629             for (int i = 0; i != Successors; ++i)
    630               ComplexEdgeSuccs.insert(TI->getSuccessor(i));
    631           }
    632 
    633           Edge += Successors;
    634         }
    635       }
    636 
    637       if (!ComplexEdgePreds.empty()) {
    638         GlobalVariable *EdgeTable =
    639           buildEdgeLookupTable(F, Counters,
    640                                ComplexEdgePreds, ComplexEdgeSuccs);
    641         GlobalVariable *EdgeState = getEdgeStateValue();
    642 
    643         for (int i = 0, e = ComplexEdgePreds.size(); i != e; ++i) {
    644           IRBuilder<> Builder(ComplexEdgePreds[i + 1]->getFirstInsertionPt());
    645           Builder.CreateStore(Builder.getInt32(i), EdgeState);
    646         }
    647 
    648         for (int i = 0, e = ComplexEdgeSuccs.size(); i != e; ++i) {
    649           // Call runtime to perform increment.
    650           IRBuilder<> Builder(ComplexEdgeSuccs[i+1]->getFirstInsertionPt());
    651           Value *CounterPtrArray =
    652             Builder.CreateConstInBoundsGEP2_64(EdgeTable, 0,
    653                                                i * ComplexEdgePreds.size());
    654 
    655           // Build code to increment the counter.
    656           InsertIndCounterIncrCode = true;
    657           Builder.CreateCall2(getIncrementIndirectCounterFunc(),
    658                               EdgeState, CounterPtrArray);
    659         }
    660       }
    661     }
    662 
    663     Function *WriteoutF = insertCounterWriteout(CountersBySP);
    664     Function *FlushF = insertFlush(CountersBySP);
    665 
    666     // Create a small bit of code that registers the "__llvm_gcov_writeout" to
    667     // be executed at exit and the "__llvm_gcov_flush" function to be executed
    668     // when "__gcov_flush" is called.
    669     FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
    670     Function *F = Function::Create(FTy, GlobalValue::InternalLinkage,
    671                                    "__llvm_gcov_init", M);
    672     F->setUnnamedAddr(true);
    673     F->setLinkage(GlobalValue::InternalLinkage);
    674     F->addFnAttr(Attribute::NoInline);
    675     if (Options.NoRedZone)
    676       F->addFnAttr(Attribute::NoRedZone);
    677 
    678     BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", F);
    679     IRBuilder<> Builder(BB);
    680 
    681     FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
    682     Type *Params[] = {
    683       PointerType::get(FTy, 0),
    684       PointerType::get(FTy, 0)
    685     };
    686     FTy = FunctionType::get(Builder.getVoidTy(), Params, false);
    687 
    688     // Initialize the environment and register the local writeout and flush
    689     // functions.
    690     Constant *GCOVInit = M->getOrInsertFunction("llvm_gcov_init", FTy);
    691     Builder.CreateCall2(GCOVInit, WriteoutF, FlushF);
    692     Builder.CreateRetVoid();
    693 
    694     appendToGlobalCtors(*M, F, 0);
    695   }
    696 
    697   if (InsertIndCounterIncrCode)
    698     insertIndirectCounterIncrement();
    699 
    700   return Result;
    701 }
    702 
    703 // All edges with successors that aren't branches are "complex", because it
    704 // requires complex logic to pick which counter to update.
    705 GlobalVariable *GCOVProfiler::buildEdgeLookupTable(
    706     Function *F,
    707     GlobalVariable *Counters,
    708     const UniqueVector<BasicBlock *> &Preds,
    709     const UniqueVector<BasicBlock *> &Succs) {
    710   // TODO: support invoke, threads. We rely on the fact that nothing can modify
    711   // the whole-Module pred edge# between the time we set it and the time we next
    712   // read it. Threads and invoke make this untrue.
    713 
    714   // emit [(succs * preds) x i64*], logically [succ x [pred x i64*]].
    715   size_t TableSize = Succs.size() * Preds.size();
    716   Type *Int64PtrTy = Type::getInt64PtrTy(*Ctx);
    717   ArrayType *EdgeTableTy = ArrayType::get(Int64PtrTy, TableSize);
    718 
    719   std::unique_ptr<Constant * []> EdgeTable(new Constant *[TableSize]);
    720   Constant *NullValue = Constant::getNullValue(Int64PtrTy);
    721   for (size_t i = 0; i != TableSize; ++i)
    722     EdgeTable[i] = NullValue;
    723 
    724   unsigned Edge = 0;
    725   for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
    726     TerminatorInst *TI = BB->getTerminator();
    727     int Successors = isa<ReturnInst>(TI) ? 1 : TI->getNumSuccessors();
    728     if (Successors > 1 && !isa<BranchInst>(TI) && !isa<ReturnInst>(TI)) {
    729       for (int i = 0; i != Successors; ++i) {
    730         BasicBlock *Succ = TI->getSuccessor(i);
    731         IRBuilder<> Builder(Succ);
    732         Value *Counter = Builder.CreateConstInBoundsGEP2_64(Counters, 0,
    733                                                             Edge + i);
    734         EdgeTable[((Succs.idFor(Succ)-1) * Preds.size()) +
    735                   (Preds.idFor(BB)-1)] = cast<Constant>(Counter);
    736       }
    737     }
    738     Edge += Successors;
    739   }
    740 
    741   ArrayRef<Constant*> V(&EdgeTable[0], TableSize);
    742   GlobalVariable *EdgeTableGV =
    743       new GlobalVariable(
    744           *M, EdgeTableTy, true, GlobalValue::InternalLinkage,
    745           ConstantArray::get(EdgeTableTy, V),
    746           "__llvm_gcda_edge_table");
    747   EdgeTableGV->setUnnamedAddr(true);
    748   return EdgeTableGV;
    749 }
    750 
    751 Constant *GCOVProfiler::getStartFileFunc() {
    752   Type *Args[] = {
    753     Type::getInt8PtrTy(*Ctx),  // const char *orig_filename
    754     Type::getInt8PtrTy(*Ctx),  // const char version[4]
    755     Type::getInt32Ty(*Ctx),    // uint32_t checksum
    756   };
    757   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
    758   return M->getOrInsertFunction("llvm_gcda_start_file", FTy);
    759 }
    760 
    761 Constant *GCOVProfiler::getIncrementIndirectCounterFunc() {
    762   Type *Int32Ty = Type::getInt32Ty(*Ctx);
    763   Type *Int64Ty = Type::getInt64Ty(*Ctx);
    764   Type *Args[] = {
    765     Int32Ty->getPointerTo(),                // uint32_t *predecessor
    766     Int64Ty->getPointerTo()->getPointerTo() // uint64_t **counters
    767   };
    768   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
    769   return M->getOrInsertFunction("__llvm_gcov_indirect_counter_increment", FTy);
    770 }
    771 
    772 Constant *GCOVProfiler::getEmitFunctionFunc() {
    773   Type *Args[] = {
    774     Type::getInt32Ty(*Ctx),    // uint32_t ident
    775     Type::getInt8PtrTy(*Ctx),  // const char *function_name
    776     Type::getInt32Ty(*Ctx),    // uint32_t func_checksum
    777     Type::getInt8Ty(*Ctx),     // uint8_t use_extra_checksum
    778     Type::getInt32Ty(*Ctx),    // uint32_t cfg_checksum
    779   };
    780   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
    781   return M->getOrInsertFunction("llvm_gcda_emit_function", FTy);
    782 }
    783 
    784 Constant *GCOVProfiler::getEmitArcsFunc() {
    785   Type *Args[] = {
    786     Type::getInt32Ty(*Ctx),     // uint32_t num_counters
    787     Type::getInt64PtrTy(*Ctx),  // uint64_t *counters
    788   };
    789   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
    790   return M->getOrInsertFunction("llvm_gcda_emit_arcs", FTy);
    791 }
    792 
    793 Constant *GCOVProfiler::getSummaryInfoFunc() {
    794   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
    795   return M->getOrInsertFunction("llvm_gcda_summary_info", FTy);
    796 }
    797 
    798 Constant *GCOVProfiler::getDeleteWriteoutFunctionListFunc() {
    799   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
    800   return M->getOrInsertFunction("llvm_delete_writeout_function_list", FTy);
    801 }
    802 
    803 Constant *GCOVProfiler::getDeleteFlushFunctionListFunc() {
    804   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
    805   return M->getOrInsertFunction("llvm_delete_flush_function_list", FTy);
    806 }
    807 
    808 Constant *GCOVProfiler::getEndFileFunc() {
    809   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
    810   return M->getOrInsertFunction("llvm_gcda_end_file", FTy);
    811 }
    812 
    813 GlobalVariable *GCOVProfiler::getEdgeStateValue() {
    814   GlobalVariable *GV = M->getGlobalVariable("__llvm_gcov_global_state_pred");
    815   if (!GV) {
    816     GV = new GlobalVariable(*M, Type::getInt32Ty(*Ctx), false,
    817                             GlobalValue::InternalLinkage,
    818                             ConstantInt::get(Type::getInt32Ty(*Ctx),
    819                                              0xffffffff),
    820                             "__llvm_gcov_global_state_pred");
    821     GV->setUnnamedAddr(true);
    822   }
    823   return GV;
    824 }
    825 
    826 Function *GCOVProfiler::insertCounterWriteout(
    827     ArrayRef<std::pair<GlobalVariable *, MDNode *> > CountersBySP) {
    828   FunctionType *WriteoutFTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
    829   Function *WriteoutF = M->getFunction("__llvm_gcov_writeout");
    830   if (!WriteoutF)
    831     WriteoutF = Function::Create(WriteoutFTy, GlobalValue::InternalLinkage,
    832                                  "__llvm_gcov_writeout", M);
    833   WriteoutF->setUnnamedAddr(true);
    834   WriteoutF->addFnAttr(Attribute::NoInline);
    835   if (Options.NoRedZone)
    836     WriteoutF->addFnAttr(Attribute::NoRedZone);
    837 
    838   BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", WriteoutF);
    839   IRBuilder<> Builder(BB);
    840 
    841   Constant *StartFile = getStartFileFunc();
    842   Constant *EmitFunction = getEmitFunctionFunc();
    843   Constant *EmitArcs = getEmitArcsFunc();
    844   Constant *SummaryInfo = getSummaryInfoFunc();
    845   Constant *EndFile = getEndFileFunc();
    846 
    847   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
    848   if (CU_Nodes) {
    849     for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
    850       DICompileUnit CU(CU_Nodes->getOperand(i));
    851       std::string FilenameGcda = mangleName(CU, "gcda");
    852       uint32_t CfgChecksum = FileChecksums.empty() ? 0 : FileChecksums[i];
    853       Builder.CreateCall3(StartFile,
    854                           Builder.CreateGlobalStringPtr(FilenameGcda),
    855                           Builder.CreateGlobalStringPtr(ReversedVersion),
    856                           Builder.getInt32(CfgChecksum));
    857       for (unsigned j = 0, e = CountersBySP.size(); j != e; ++j) {
    858         DISubprogram SP(CountersBySP[j].second);
    859         uint32_t FuncChecksum = Funcs.empty() ? 0 : Funcs[j]->getFuncChecksum();
    860         Builder.CreateCall5(
    861             EmitFunction, Builder.getInt32(j),
    862             Options.FunctionNamesInData ?
    863               Builder.CreateGlobalStringPtr(getFunctionName(SP)) :
    864               Constant::getNullValue(Builder.getInt8PtrTy()),
    865             Builder.getInt32(FuncChecksum),
    866             Builder.getInt8(Options.UseCfgChecksum),
    867             Builder.getInt32(CfgChecksum));
    868 
    869         GlobalVariable *GV = CountersBySP[j].first;
    870         unsigned Arcs =
    871           cast<ArrayType>(GV->getType()->getElementType())->getNumElements();
    872         Builder.CreateCall2(EmitArcs,
    873                             Builder.getInt32(Arcs),
    874                             Builder.CreateConstGEP2_64(GV, 0, 0));
    875       }
    876       Builder.CreateCall(SummaryInfo);
    877       Builder.CreateCall(EndFile);
    878     }
    879   }
    880 
    881   Builder.CreateRetVoid();
    882   return WriteoutF;
    883 }
    884 
    885 void GCOVProfiler::insertIndirectCounterIncrement() {
    886   Function *Fn =
    887     cast<Function>(GCOVProfiler::getIncrementIndirectCounterFunc());
    888   Fn->setUnnamedAddr(true);
    889   Fn->setLinkage(GlobalValue::InternalLinkage);
    890   Fn->addFnAttr(Attribute::NoInline);
    891   if (Options.NoRedZone)
    892     Fn->addFnAttr(Attribute::NoRedZone);
    893 
    894   // Create basic blocks for function.
    895   BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", Fn);
    896   IRBuilder<> Builder(BB);
    897 
    898   BasicBlock *PredNotNegOne = BasicBlock::Create(*Ctx, "", Fn);
    899   BasicBlock *CounterEnd = BasicBlock::Create(*Ctx, "", Fn);
    900   BasicBlock *Exit = BasicBlock::Create(*Ctx, "exit", Fn);
    901 
    902   // uint32_t pred = *predecessor;
    903   // if (pred == 0xffffffff) return;
    904   Argument *Arg = Fn->arg_begin();
    905   Arg->setName("predecessor");
    906   Value *Pred = Builder.CreateLoad(Arg, "pred");
    907   Value *Cond = Builder.CreateICmpEQ(Pred, Builder.getInt32(0xffffffff));
    908   BranchInst::Create(Exit, PredNotNegOne, Cond, BB);
    909 
    910   Builder.SetInsertPoint(PredNotNegOne);
    911 
    912   // uint64_t *counter = counters[pred];
    913   // if (!counter) return;
    914   Value *ZExtPred = Builder.CreateZExt(Pred, Builder.getInt64Ty());
    915   Arg = std::next(Fn->arg_begin());
    916   Arg->setName("counters");
    917   Value *GEP = Builder.CreateGEP(Arg, ZExtPred);
    918   Value *Counter = Builder.CreateLoad(GEP, "counter");
    919   Cond = Builder.CreateICmpEQ(Counter,
    920                               Constant::getNullValue(
    921                                   Builder.getInt64Ty()->getPointerTo()));
    922   Builder.CreateCondBr(Cond, Exit, CounterEnd);
    923 
    924   // ++*counter;
    925   Builder.SetInsertPoint(CounterEnd);
    926   Value *Add = Builder.CreateAdd(Builder.CreateLoad(Counter),
    927                                  Builder.getInt64(1));
    928   Builder.CreateStore(Add, Counter);
    929   Builder.CreateBr(Exit);
    930 
    931   // Fill in the exit block.
    932   Builder.SetInsertPoint(Exit);
    933   Builder.CreateRetVoid();
    934 }
    935 
    936 Function *GCOVProfiler::
    937 insertFlush(ArrayRef<std::pair<GlobalVariable*, MDNode*> > CountersBySP) {
    938   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
    939   Function *FlushF = M->getFunction("__llvm_gcov_flush");
    940   if (!FlushF)
    941     FlushF = Function::Create(FTy, GlobalValue::InternalLinkage,
    942                               "__llvm_gcov_flush", M);
    943   else
    944     FlushF->setLinkage(GlobalValue::InternalLinkage);
    945   FlushF->setUnnamedAddr(true);
    946   FlushF->addFnAttr(Attribute::NoInline);
    947   if (Options.NoRedZone)
    948     FlushF->addFnAttr(Attribute::NoRedZone);
    949 
    950   BasicBlock *Entry = BasicBlock::Create(*Ctx, "entry", FlushF);
    951 
    952   // Write out the current counters.
    953   Constant *WriteoutF = M->getFunction("__llvm_gcov_writeout");
    954   assert(WriteoutF && "Need to create the writeout function first!");
    955 
    956   IRBuilder<> Builder(Entry);
    957   Builder.CreateCall(WriteoutF);
    958 
    959   // Zero out the counters.
    960   for (ArrayRef<std::pair<GlobalVariable *, MDNode *> >::iterator
    961          I = CountersBySP.begin(), E = CountersBySP.end();
    962        I != E; ++I) {
    963     GlobalVariable *GV = I->first;
    964     Constant *Null = Constant::getNullValue(GV->getType()->getElementType());
    965     Builder.CreateStore(Null, GV);
    966   }
    967 
    968   Type *RetTy = FlushF->getReturnType();
    969   if (RetTy == Type::getVoidTy(*Ctx))
    970     Builder.CreateRetVoid();
    971   else if (RetTy->isIntegerTy())
    972     // Used if __llvm_gcov_flush was implicitly declared.
    973     Builder.CreateRet(ConstantInt::get(RetTy, 0));
    974   else
    975     report_fatal_error("invalid return type for __llvm_gcov_flush");
    976 
    977   return FlushF;
    978 }
    979