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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 static cl::opt<bool> DefaultExitBlockBeforeBody("gcov-exit-block-before-body",
     51                                                 cl::init(false), cl::Hidden);
     52 
     53 GCOVOptions GCOVOptions::getDefault() {
     54   GCOVOptions Options;
     55   Options.EmitNotes = true;
     56   Options.EmitData = true;
     57   Options.UseCfgChecksum = false;
     58   Options.NoRedZone = false;
     59   Options.FunctionNamesInData = true;
     60   Options.ExitBlockBeforeBody = DefaultExitBlockBeforeBody;
     61 
     62   if (DefaultGCOVVersion.size() != 4) {
     63     llvm::report_fatal_error(std::string("Invalid -default-gcov-version: ") +
     64                              DefaultGCOVVersion);
     65   }
     66   memcpy(Options.Version, DefaultGCOVVersion.c_str(), 4);
     67   return Options;
     68 }
     69 
     70 namespace {
     71   class GCOVFunction;
     72 
     73   class GCOVProfiler : public ModulePass {
     74   public:
     75     static char ID;
     76     GCOVProfiler() : GCOVProfiler(GCOVOptions::getDefault()) {}
     77     GCOVProfiler(const GCOVOptions &Opts) : ModulePass(ID), Options(Opts) {
     78       assert((Options.EmitNotes || Options.EmitData) &&
     79              "GCOVProfiler asked to do nothing?");
     80       ReversedVersion[0] = Options.Version[3];
     81       ReversedVersion[1] = Options.Version[2];
     82       ReversedVersion[2] = Options.Version[1];
     83       ReversedVersion[3] = Options.Version[0];
     84       ReversedVersion[4] = '\0';
     85       initializeGCOVProfilerPass(*PassRegistry::getPassRegistry());
     86     }
     87     const char *getPassName() const override {
     88       return "GCOV Profiler";
     89     }
     90 
     91   private:
     92     bool runOnModule(Module &M) override;
     93 
     94     // Create the .gcno files for the Module based on DebugInfo.
     95     void emitProfileNotes();
     96 
     97     // Modify the program to track transitions along edges and call into the
     98     // profiling runtime to emit .gcda files when run.
     99     bool emitProfileArcs();
    100 
    101     // Get pointers to the functions in the runtime library.
    102     Constant *getStartFileFunc();
    103     Constant *getIncrementIndirectCounterFunc();
    104     Constant *getEmitFunctionFunc();
    105     Constant *getEmitArcsFunc();
    106     Constant *getSummaryInfoFunc();
    107     Constant *getDeleteWriteoutFunctionListFunc();
    108     Constant *getDeleteFlushFunctionListFunc();
    109     Constant *getEndFileFunc();
    110 
    111     // Create or retrieve an i32 state value that is used to represent the
    112     // pred block number for certain non-trivial edges.
    113     GlobalVariable *getEdgeStateValue();
    114 
    115     // Produce a table of pointers to counters, by predecessor and successor
    116     // block number.
    117     GlobalVariable *buildEdgeLookupTable(Function *F,
    118                                          GlobalVariable *Counter,
    119                                          const UniqueVector<BasicBlock *>&Preds,
    120                                          const UniqueVector<BasicBlock*>&Succs);
    121 
    122     // Add the function to write out all our counters to the global destructor
    123     // list.
    124     Function *insertCounterWriteout(ArrayRef<std::pair<GlobalVariable*,
    125                                                        MDNode*> >);
    126     Function *insertFlush(ArrayRef<std::pair<GlobalVariable*, MDNode*> >);
    127     void insertIndirectCounterIncrement();
    128 
    129     std::string mangleName(const DICompileUnit *CU, const char *NewStem);
    130 
    131     GCOVOptions Options;
    132 
    133     // Reversed, NUL-terminated copy of Options.Version.
    134     char ReversedVersion[5];
    135     // Checksum, produced by hash of EdgeDestinations
    136     SmallVector<uint32_t, 4> FileChecksums;
    137 
    138     Module *M;
    139     LLVMContext *Ctx;
    140     SmallVector<std::unique_ptr<GCOVFunction>, 16> Funcs;
    141     DenseMap<DISubprogram *, Function *> FnMap;
    142   };
    143 }
    144 
    145 char GCOVProfiler::ID = 0;
    146 INITIALIZE_PASS(GCOVProfiler, "insert-gcov-profiling",
    147                 "Insert instrumentation for GCOV profiling", false, false)
    148 
    149 ModulePass *llvm::createGCOVProfilerPass(const GCOVOptions &Options) {
    150   return new GCOVProfiler(Options);
    151 }
    152 
    153 static StringRef getFunctionName(const DISubprogram *SP) {
    154   if (!SP->getLinkageName().empty())
    155     return SP->getLinkageName();
    156   return SP->getName();
    157 }
    158 
    159 namespace {
    160   class GCOVRecord {
    161    protected:
    162     static const char *const LinesTag;
    163     static const char *const FunctionTag;
    164     static const char *const BlockTag;
    165     static const char *const EdgeTag;
    166 
    167     GCOVRecord() = default;
    168 
    169     void writeBytes(const char *Bytes, int Size) {
    170       os->write(Bytes, Size);
    171     }
    172 
    173     void write(uint32_t i) {
    174       writeBytes(reinterpret_cast<char*>(&i), 4);
    175     }
    176 
    177     // Returns the length measured in 4-byte blocks that will be used to
    178     // represent this string in a GCOV file
    179     static unsigned lengthOfGCOVString(StringRef s) {
    180       // A GCOV string is a length, followed by a NUL, then between 0 and 3 NULs
    181       // padding out to the next 4-byte word. The length is measured in 4-byte
    182       // words including padding, not bytes of actual string.
    183       return (s.size() / 4) + 1;
    184     }
    185 
    186     void writeGCOVString(StringRef s) {
    187       uint32_t Len = lengthOfGCOVString(s);
    188       write(Len);
    189       writeBytes(s.data(), s.size());
    190 
    191       // Write 1 to 4 bytes of NUL padding.
    192       assert((unsigned)(4 - (s.size() % 4)) > 0);
    193       assert((unsigned)(4 - (s.size() % 4)) <= 4);
    194       writeBytes("\0\0\0\0", 4 - (s.size() % 4));
    195     }
    196 
    197     raw_ostream *os;
    198   };
    199   const char *const GCOVRecord::LinesTag = "\0\0\x45\x01";
    200   const char *const GCOVRecord::FunctionTag = "\0\0\0\1";
    201   const char *const GCOVRecord::BlockTag = "\0\0\x41\x01";
    202   const char *const GCOVRecord::EdgeTag = "\0\0\x43\x01";
    203 
    204   class GCOVFunction;
    205   class GCOVBlock;
    206 
    207   // Constructed only by requesting it from a GCOVBlock, this object stores a
    208   // list of line numbers and a single filename, representing lines that belong
    209   // to the block.
    210   class GCOVLines : public GCOVRecord {
    211    public:
    212     void addLine(uint32_t Line) {
    213       assert(Line != 0 && "Line zero is not a valid real line number.");
    214       Lines.push_back(Line);
    215     }
    216 
    217     uint32_t length() const {
    218       // Here 2 = 1 for string length + 1 for '0' id#.
    219       return lengthOfGCOVString(Filename) + 2 + Lines.size();
    220     }
    221 
    222     void writeOut() {
    223       write(0);
    224       writeGCOVString(Filename);
    225       for (int i = 0, e = Lines.size(); i != e; ++i)
    226         write(Lines[i]);
    227     }
    228 
    229     GCOVLines(StringRef F, raw_ostream *os)
    230       : Filename(F) {
    231       this->os = os;
    232     }
    233 
    234    private:
    235     StringRef Filename;
    236     SmallVector<uint32_t, 32> Lines;
    237   };
    238 
    239 
    240   // Represent a basic block in GCOV. Each block has a unique number in the
    241   // function, number of lines belonging to each block, and a set of edges to
    242   // other blocks.
    243   class GCOVBlock : public GCOVRecord {
    244    public:
    245     GCOVLines &getFile(StringRef Filename) {
    246       GCOVLines *&Lines = LinesByFile[Filename];
    247       if (!Lines) {
    248         Lines = new GCOVLines(Filename, os);
    249       }
    250       return *Lines;
    251     }
    252 
    253     void addEdge(GCOVBlock &Successor) {
    254       OutEdges.push_back(&Successor);
    255     }
    256 
    257     void writeOut() {
    258       uint32_t Len = 3;
    259       SmallVector<StringMapEntry<GCOVLines *> *, 32> SortedLinesByFile;
    260       for (StringMap<GCOVLines *>::iterator I = LinesByFile.begin(),
    261                E = LinesByFile.end(); I != E; ++I) {
    262         Len += I->second->length();
    263         SortedLinesByFile.push_back(&*I);
    264       }
    265 
    266       writeBytes(LinesTag, 4);
    267       write(Len);
    268       write(Number);
    269 
    270       std::sort(SortedLinesByFile.begin(), SortedLinesByFile.end(),
    271                 [](StringMapEntry<GCOVLines *> *LHS,
    272                    StringMapEntry<GCOVLines *> *RHS) {
    273         return LHS->getKey() < RHS->getKey();
    274       });
    275       for (SmallVectorImpl<StringMapEntry<GCOVLines *> *>::iterator
    276                I = SortedLinesByFile.begin(), E = SortedLinesByFile.end();
    277            I != E; ++I)
    278         (*I)->getValue()->writeOut();
    279       write(0);
    280       write(0);
    281     }
    282 
    283     ~GCOVBlock() {
    284       DeleteContainerSeconds(LinesByFile);
    285     }
    286 
    287     GCOVBlock(const GCOVBlock &RHS) : GCOVRecord(RHS), Number(RHS.Number) {
    288       // Only allow copy before edges and lines have been added. After that,
    289       // there are inter-block pointers (eg: edges) that won't take kindly to
    290       // blocks being copied or moved around.
    291       assert(LinesByFile.empty());
    292       assert(OutEdges.empty());
    293     }
    294 
    295    private:
    296     friend class GCOVFunction;
    297 
    298     GCOVBlock(uint32_t Number, raw_ostream *os)
    299         : Number(Number) {
    300       this->os = os;
    301     }
    302 
    303     uint32_t Number;
    304     StringMap<GCOVLines *> LinesByFile;
    305     SmallVector<GCOVBlock *, 4> OutEdges;
    306   };
    307 
    308   // A function has a unique identifier, a checksum (we leave as zero) and a
    309   // set of blocks and a map of edges between blocks. This is the only GCOV
    310   // object users can construct, the blocks and lines will be rooted here.
    311   class GCOVFunction : public GCOVRecord {
    312    public:
    313      GCOVFunction(const DISubprogram *SP, Function *F, raw_ostream *os,
    314                   uint32_t Ident, bool UseCfgChecksum, bool ExitBlockBeforeBody)
    315          : SP(SP), Ident(Ident), UseCfgChecksum(UseCfgChecksum), CfgChecksum(0),
    316            ReturnBlock(1, os) {
    317       this->os = os;
    318 
    319       DEBUG(dbgs() << "Function: " << getFunctionName(SP) << "\n");
    320 
    321       uint32_t i = 0;
    322       for (auto &BB : *F) {
    323         // Skip index 1 if it's assigned to the ReturnBlock.
    324         if (i == 1 && ExitBlockBeforeBody)
    325           ++i;
    326         Blocks.insert(std::make_pair(&BB, GCOVBlock(i++, os)));
    327       }
    328       if (!ExitBlockBeforeBody)
    329         ReturnBlock.Number = i;
    330 
    331       std::string FunctionNameAndLine;
    332       raw_string_ostream FNLOS(FunctionNameAndLine);
    333       FNLOS << getFunctionName(SP) << SP->getLine();
    334       FNLOS.flush();
    335       FuncChecksum = hash_value(FunctionNameAndLine);
    336     }
    337 
    338     GCOVBlock &getBlock(BasicBlock *BB) {
    339       return Blocks.find(BB)->second;
    340     }
    341 
    342     GCOVBlock &getReturnBlock() {
    343       return ReturnBlock;
    344     }
    345 
    346     std::string getEdgeDestinations() {
    347       std::string EdgeDestinations;
    348       raw_string_ostream EDOS(EdgeDestinations);
    349       Function *F = Blocks.begin()->first->getParent();
    350       for (BasicBlock &I : *F) {
    351         GCOVBlock &Block = getBlock(&I);
    352         for (int i = 0, e = Block.OutEdges.size(); i != e; ++i)
    353           EDOS << Block.OutEdges[i]->Number;
    354       }
    355       return EdgeDestinations;
    356     }
    357 
    358     uint32_t getFuncChecksum() {
    359       return FuncChecksum;
    360     }
    361 
    362     void setCfgChecksum(uint32_t Checksum) {
    363       CfgChecksum = Checksum;
    364     }
    365 
    366     void writeOut() {
    367       writeBytes(FunctionTag, 4);
    368       uint32_t BlockLen = 1 + 1 + 1 + lengthOfGCOVString(getFunctionName(SP)) +
    369                           1 + lengthOfGCOVString(SP->getFilename()) + 1;
    370       if (UseCfgChecksum)
    371         ++BlockLen;
    372       write(BlockLen);
    373       write(Ident);
    374       write(FuncChecksum);
    375       if (UseCfgChecksum)
    376         write(CfgChecksum);
    377       writeGCOVString(getFunctionName(SP));
    378       writeGCOVString(SP->getFilename());
    379       write(SP->getLine());
    380 
    381       // Emit count of blocks.
    382       writeBytes(BlockTag, 4);
    383       write(Blocks.size() + 1);
    384       for (int i = 0, e = Blocks.size() + 1; i != e; ++i) {
    385         write(0);  // No flags on our blocks.
    386       }
    387       DEBUG(dbgs() << Blocks.size() << " blocks.\n");
    388 
    389       // Emit edges between blocks.
    390       if (Blocks.empty()) return;
    391       Function *F = Blocks.begin()->first->getParent();
    392       for (BasicBlock &I : *F) {
    393         GCOVBlock &Block = getBlock(&I);
    394         if (Block.OutEdges.empty()) continue;
    395 
    396         writeBytes(EdgeTag, 4);
    397         write(Block.OutEdges.size() * 2 + 1);
    398         write(Block.Number);
    399         for (int i = 0, e = Block.OutEdges.size(); i != e; ++i) {
    400           DEBUG(dbgs() << Block.Number << " -> " << Block.OutEdges[i]->Number
    401                        << "\n");
    402           write(Block.OutEdges[i]->Number);
    403           write(0);  // no flags
    404         }
    405       }
    406 
    407       // Emit lines for each block.
    408       for (BasicBlock &I : *F)
    409         getBlock(&I).writeOut();
    410     }
    411 
    412    private:
    413      const DISubprogram *SP;
    414     uint32_t Ident;
    415     uint32_t FuncChecksum;
    416     bool UseCfgChecksum;
    417     uint32_t CfgChecksum;
    418     DenseMap<BasicBlock *, GCOVBlock> Blocks;
    419     GCOVBlock ReturnBlock;
    420   };
    421 }
    422 
    423 std::string GCOVProfiler::mangleName(const DICompileUnit *CU,
    424                                      const char *NewStem) {
    425   if (NamedMDNode *GCov = M->getNamedMetadata("llvm.gcov")) {
    426     for (int i = 0, e = GCov->getNumOperands(); i != e; ++i) {
    427       MDNode *N = GCov->getOperand(i);
    428       if (N->getNumOperands() != 2) continue;
    429       MDString *GCovFile = dyn_cast<MDString>(N->getOperand(0));
    430       MDNode *CompileUnit = dyn_cast<MDNode>(N->getOperand(1));
    431       if (!GCovFile || !CompileUnit) continue;
    432       if (CompileUnit == CU) {
    433         SmallString<128> Filename = GCovFile->getString();
    434         sys::path::replace_extension(Filename, NewStem);
    435         return Filename.str();
    436       }
    437     }
    438   }
    439 
    440   SmallString<128> Filename = CU->getFilename();
    441   sys::path::replace_extension(Filename, NewStem);
    442   StringRef FName = sys::path::filename(Filename);
    443   SmallString<128> CurPath;
    444   if (sys::fs::current_path(CurPath)) return FName;
    445   sys::path::append(CurPath, FName);
    446   return CurPath.str();
    447 }
    448 
    449 bool GCOVProfiler::runOnModule(Module &M) {
    450   this->M = &M;
    451   Ctx = &M.getContext();
    452 
    453   FnMap.clear();
    454   for (Function &F : M) {
    455     if (DISubprogram *SP = F.getSubprogram())
    456       FnMap[SP] = &F;
    457   }
    458 
    459   if (Options.EmitNotes) emitProfileNotes();
    460   if (Options.EmitData) return emitProfileArcs();
    461   return false;
    462 }
    463 
    464 static bool functionHasLines(Function *F) {
    465   // Check whether this function actually has any source lines. Not only
    466   // do these waste space, they also can crash gcov.
    467   for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
    468     for (BasicBlock::iterator I = BB->begin(), IE = BB->end();
    469          I != IE; ++I) {
    470       // Debug intrinsic locations correspond to the location of the
    471       // declaration, not necessarily any statements or expressions.
    472       if (isa<DbgInfoIntrinsic>(I)) continue;
    473 
    474       const DebugLoc &Loc = I->getDebugLoc();
    475       if (!Loc)
    476         continue;
    477 
    478       // Artificial lines such as calls to the global constructors.
    479       if (Loc.getLine() == 0) continue;
    480 
    481       return true;
    482     }
    483   }
    484   return false;
    485 }
    486 
    487 void GCOVProfiler::emitProfileNotes() {
    488   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
    489   if (!CU_Nodes) return;
    490 
    491   for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
    492     // Each compile unit gets its own .gcno file. This means that whether we run
    493     // this pass over the original .o's as they're produced, or run it after
    494     // LTO, we'll generate the same .gcno files.
    495 
    496     auto *CU = cast<DICompileUnit>(CU_Nodes->getOperand(i));
    497     std::error_code EC;
    498     raw_fd_ostream out(mangleName(CU, "gcno"), EC, sys::fs::F_None);
    499     std::string EdgeDestinations;
    500 
    501     unsigned FunctionIdent = 0;
    502     for (auto *SP : CU->getSubprograms()) {
    503       Function *F = FnMap[SP];
    504       if (!F) continue;
    505       if (!functionHasLines(F)) continue;
    506 
    507       // gcov expects every function to start with an entry block that has a
    508       // single successor, so split the entry block to make sure of that.
    509       BasicBlock &EntryBlock = F->getEntryBlock();
    510       BasicBlock::iterator It = EntryBlock.begin();
    511       while (isa<AllocaInst>(*It) || isa<DbgInfoIntrinsic>(*It))
    512         ++It;
    513       EntryBlock.splitBasicBlock(It);
    514 
    515       Funcs.push_back(make_unique<GCOVFunction>(SP, F, &out, FunctionIdent++,
    516                                                 Options.UseCfgChecksum,
    517                                                 Options.ExitBlockBeforeBody));
    518       GCOVFunction &Func = *Funcs.back();
    519 
    520       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
    521         GCOVBlock &Block = Func.getBlock(&*BB);
    522         TerminatorInst *TI = BB->getTerminator();
    523         if (int successors = TI->getNumSuccessors()) {
    524           for (int i = 0; i != successors; ++i) {
    525             Block.addEdge(Func.getBlock(TI->getSuccessor(i)));
    526           }
    527         } else if (isa<ReturnInst>(TI)) {
    528           Block.addEdge(Func.getReturnBlock());
    529         }
    530 
    531         uint32_t Line = 0;
    532         for (BasicBlock::iterator I = BB->begin(), IE = BB->end();
    533              I != IE; ++I) {
    534           // Debug intrinsic locations correspond to the location of the
    535           // declaration, not necessarily any statements or expressions.
    536           if (isa<DbgInfoIntrinsic>(I)) continue;
    537 
    538           const DebugLoc &Loc = I->getDebugLoc();
    539           if (!Loc)
    540             continue;
    541 
    542           // Artificial lines such as calls to the global constructors.
    543           if (Loc.getLine() == 0) continue;
    544 
    545           if (Line == Loc.getLine()) continue;
    546           Line = Loc.getLine();
    547           if (SP != getDISubprogram(Loc.getScope()))
    548             continue;
    549 
    550           GCOVLines &Lines = Block.getFile(SP->getFilename());
    551           Lines.addLine(Loc.getLine());
    552         }
    553       }
    554       EdgeDestinations += Func.getEdgeDestinations();
    555     }
    556 
    557     FileChecksums.push_back(hash_value(EdgeDestinations));
    558     out.write("oncg", 4);
    559     out.write(ReversedVersion, 4);
    560     out.write(reinterpret_cast<char*>(&FileChecksums.back()), 4);
    561 
    562     for (auto &Func : Funcs) {
    563       Func->setCfgChecksum(FileChecksums.back());
    564       Func->writeOut();
    565     }
    566 
    567     out.write("\0\0\0\0\0\0\0\0", 8);  // EOF
    568     out.close();
    569   }
    570 }
    571 
    572 bool GCOVProfiler::emitProfileArcs() {
    573   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
    574   if (!CU_Nodes) return false;
    575 
    576   bool Result = false;
    577   bool InsertIndCounterIncrCode = false;
    578   for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
    579     auto *CU = cast<DICompileUnit>(CU_Nodes->getOperand(i));
    580     SmallVector<std::pair<GlobalVariable *, MDNode *>, 8> CountersBySP;
    581     for (auto *SP : CU->getSubprograms()) {
    582       Function *F = FnMap[SP];
    583       if (!F) continue;
    584       if (!functionHasLines(F)) continue;
    585       if (!Result) Result = true;
    586       unsigned Edges = 0;
    587       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
    588         TerminatorInst *TI = BB->getTerminator();
    589         if (isa<ReturnInst>(TI))
    590           ++Edges;
    591         else
    592           Edges += TI->getNumSuccessors();
    593       }
    594 
    595       ArrayType *CounterTy =
    596         ArrayType::get(Type::getInt64Ty(*Ctx), Edges);
    597       GlobalVariable *Counters =
    598         new GlobalVariable(*M, CounterTy, false,
    599                            GlobalValue::InternalLinkage,
    600                            Constant::getNullValue(CounterTy),
    601                            "__llvm_gcov_ctr");
    602       CountersBySP.push_back(std::make_pair(Counters, SP));
    603 
    604       UniqueVector<BasicBlock *> ComplexEdgePreds;
    605       UniqueVector<BasicBlock *> ComplexEdgeSuccs;
    606 
    607       unsigned Edge = 0;
    608       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
    609         TerminatorInst *TI = BB->getTerminator();
    610         int Successors = isa<ReturnInst>(TI) ? 1 : TI->getNumSuccessors();
    611         if (Successors) {
    612           if (Successors == 1) {
    613             IRBuilder<> Builder(&*BB->getFirstInsertionPt());
    614             Value *Counter = Builder.CreateConstInBoundsGEP2_64(Counters, 0,
    615                                                                 Edge);
    616             Value *Count = Builder.CreateLoad(Counter);
    617             Count = Builder.CreateAdd(Count, Builder.getInt64(1));
    618             Builder.CreateStore(Count, Counter);
    619           } else if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
    620             IRBuilder<> Builder(BI);
    621             Value *Sel = Builder.CreateSelect(BI->getCondition(),
    622                                               Builder.getInt64(Edge),
    623                                               Builder.getInt64(Edge + 1));
    624             SmallVector<Value *, 2> Idx;
    625             Idx.push_back(Builder.getInt64(0));
    626             Idx.push_back(Sel);
    627             Value *Counter = Builder.CreateInBoundsGEP(Counters->getValueType(),
    628                                                        Counters, Idx);
    629             Value *Count = Builder.CreateLoad(Counter);
    630             Count = Builder.CreateAdd(Count, Builder.getInt64(1));
    631             Builder.CreateStore(Count, Counter);
    632           } else {
    633             ComplexEdgePreds.insert(&*BB);
    634             for (int i = 0; i != Successors; ++i)
    635               ComplexEdgeSuccs.insert(TI->getSuccessor(i));
    636           }
    637 
    638           Edge += Successors;
    639         }
    640       }
    641 
    642       if (!ComplexEdgePreds.empty()) {
    643         GlobalVariable *EdgeTable =
    644           buildEdgeLookupTable(F, Counters,
    645                                ComplexEdgePreds, ComplexEdgeSuccs);
    646         GlobalVariable *EdgeState = getEdgeStateValue();
    647 
    648         for (int i = 0, e = ComplexEdgePreds.size(); i != e; ++i) {
    649           IRBuilder<> Builder(&*ComplexEdgePreds[i + 1]->getFirstInsertionPt());
    650           Builder.CreateStore(Builder.getInt32(i), EdgeState);
    651         }
    652 
    653         for (int i = 0, e = ComplexEdgeSuccs.size(); i != e; ++i) {
    654           // Call runtime to perform increment.
    655           IRBuilder<> Builder(&*ComplexEdgeSuccs[i + 1]->getFirstInsertionPt());
    656           Value *CounterPtrArray =
    657             Builder.CreateConstInBoundsGEP2_64(EdgeTable, 0,
    658                                                i * ComplexEdgePreds.size());
    659 
    660           // Build code to increment the counter.
    661           InsertIndCounterIncrCode = true;
    662           Builder.CreateCall(getIncrementIndirectCounterFunc(),
    663                              {EdgeState, CounterPtrArray});
    664         }
    665       }
    666     }
    667 
    668     Function *WriteoutF = insertCounterWriteout(CountersBySP);
    669     Function *FlushF = insertFlush(CountersBySP);
    670 
    671     // Create a small bit of code that registers the "__llvm_gcov_writeout" to
    672     // be executed at exit and the "__llvm_gcov_flush" function to be executed
    673     // when "__gcov_flush" is called.
    674     FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
    675     Function *F = Function::Create(FTy, GlobalValue::InternalLinkage,
    676                                    "__llvm_gcov_init", M);
    677     F->setUnnamedAddr(true);
    678     F->setLinkage(GlobalValue::InternalLinkage);
    679     F->addFnAttr(Attribute::NoInline);
    680     if (Options.NoRedZone)
    681       F->addFnAttr(Attribute::NoRedZone);
    682 
    683     BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", F);
    684     IRBuilder<> Builder(BB);
    685 
    686     FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
    687     Type *Params[] = {
    688       PointerType::get(FTy, 0),
    689       PointerType::get(FTy, 0)
    690     };
    691     FTy = FunctionType::get(Builder.getVoidTy(), Params, false);
    692 
    693     // Initialize the environment and register the local writeout and flush
    694     // functions.
    695     Constant *GCOVInit = M->getOrInsertFunction("llvm_gcov_init", FTy);
    696     Builder.CreateCall(GCOVInit, {WriteoutF, FlushF});
    697     Builder.CreateRetVoid();
    698 
    699     appendToGlobalCtors(*M, F, 0);
    700   }
    701 
    702   if (InsertIndCounterIncrCode)
    703     insertIndirectCounterIncrement();
    704 
    705   return Result;
    706 }
    707 
    708 // All edges with successors that aren't branches are "complex", because it
    709 // requires complex logic to pick which counter to update.
    710 GlobalVariable *GCOVProfiler::buildEdgeLookupTable(
    711     Function *F,
    712     GlobalVariable *Counters,
    713     const UniqueVector<BasicBlock *> &Preds,
    714     const UniqueVector<BasicBlock *> &Succs) {
    715   // TODO: support invoke, threads. We rely on the fact that nothing can modify
    716   // the whole-Module pred edge# between the time we set it and the time we next
    717   // read it. Threads and invoke make this untrue.
    718 
    719   // emit [(succs * preds) x i64*], logically [succ x [pred x i64*]].
    720   size_t TableSize = Succs.size() * Preds.size();
    721   Type *Int64PtrTy = Type::getInt64PtrTy(*Ctx);
    722   ArrayType *EdgeTableTy = ArrayType::get(Int64PtrTy, TableSize);
    723 
    724   std::unique_ptr<Constant * []> EdgeTable(new Constant *[TableSize]);
    725   Constant *NullValue = Constant::getNullValue(Int64PtrTy);
    726   for (size_t i = 0; i != TableSize; ++i)
    727     EdgeTable[i] = NullValue;
    728 
    729   unsigned Edge = 0;
    730   for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
    731     TerminatorInst *TI = BB->getTerminator();
    732     int Successors = isa<ReturnInst>(TI) ? 1 : TI->getNumSuccessors();
    733     if (Successors > 1 && !isa<BranchInst>(TI) && !isa<ReturnInst>(TI)) {
    734       for (int i = 0; i != Successors; ++i) {
    735         BasicBlock *Succ = TI->getSuccessor(i);
    736         IRBuilder<> Builder(Succ);
    737         Value *Counter = Builder.CreateConstInBoundsGEP2_64(Counters, 0,
    738                                                             Edge + i);
    739         EdgeTable[((Succs.idFor(Succ) - 1) * Preds.size()) +
    740                   (Preds.idFor(&*BB) - 1)] = cast<Constant>(Counter);
    741       }
    742     }
    743     Edge += Successors;
    744   }
    745 
    746   GlobalVariable *EdgeTableGV =
    747       new GlobalVariable(
    748           *M, EdgeTableTy, true, GlobalValue::InternalLinkage,
    749           ConstantArray::get(EdgeTableTy,
    750                              makeArrayRef(&EdgeTable[0],TableSize)),
    751           "__llvm_gcda_edge_table");
    752   EdgeTableGV->setUnnamedAddr(true);
    753   return EdgeTableGV;
    754 }
    755 
    756 Constant *GCOVProfiler::getStartFileFunc() {
    757   Type *Args[] = {
    758     Type::getInt8PtrTy(*Ctx),  // const char *orig_filename
    759     Type::getInt8PtrTy(*Ctx),  // const char version[4]
    760     Type::getInt32Ty(*Ctx),    // uint32_t checksum
    761   };
    762   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
    763   return M->getOrInsertFunction("llvm_gcda_start_file", FTy);
    764 }
    765 
    766 Constant *GCOVProfiler::getIncrementIndirectCounterFunc() {
    767   Type *Int32Ty = Type::getInt32Ty(*Ctx);
    768   Type *Int64Ty = Type::getInt64Ty(*Ctx);
    769   Type *Args[] = {
    770     Int32Ty->getPointerTo(),                // uint32_t *predecessor
    771     Int64Ty->getPointerTo()->getPointerTo() // uint64_t **counters
    772   };
    773   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
    774   return M->getOrInsertFunction("__llvm_gcov_indirect_counter_increment", FTy);
    775 }
    776 
    777 Constant *GCOVProfiler::getEmitFunctionFunc() {
    778   Type *Args[] = {
    779     Type::getInt32Ty(*Ctx),    // uint32_t ident
    780     Type::getInt8PtrTy(*Ctx),  // const char *function_name
    781     Type::getInt32Ty(*Ctx),    // uint32_t func_checksum
    782     Type::getInt8Ty(*Ctx),     // uint8_t use_extra_checksum
    783     Type::getInt32Ty(*Ctx),    // uint32_t cfg_checksum
    784   };
    785   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
    786   return M->getOrInsertFunction("llvm_gcda_emit_function", FTy);
    787 }
    788 
    789 Constant *GCOVProfiler::getEmitArcsFunc() {
    790   Type *Args[] = {
    791     Type::getInt32Ty(*Ctx),     // uint32_t num_counters
    792     Type::getInt64PtrTy(*Ctx),  // uint64_t *counters
    793   };
    794   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
    795   return M->getOrInsertFunction("llvm_gcda_emit_arcs", FTy);
    796 }
    797 
    798 Constant *GCOVProfiler::getSummaryInfoFunc() {
    799   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
    800   return M->getOrInsertFunction("llvm_gcda_summary_info", FTy);
    801 }
    802 
    803 Constant *GCOVProfiler::getDeleteWriteoutFunctionListFunc() {
    804   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
    805   return M->getOrInsertFunction("llvm_delete_writeout_function_list", FTy);
    806 }
    807 
    808 Constant *GCOVProfiler::getDeleteFlushFunctionListFunc() {
    809   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
    810   return M->getOrInsertFunction("llvm_delete_flush_function_list", FTy);
    811 }
    812 
    813 Constant *GCOVProfiler::getEndFileFunc() {
    814   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
    815   return M->getOrInsertFunction("llvm_gcda_end_file", FTy);
    816 }
    817 
    818 GlobalVariable *GCOVProfiler::getEdgeStateValue() {
    819   GlobalVariable *GV = M->getGlobalVariable("__llvm_gcov_global_state_pred");
    820   if (!GV) {
    821     GV = new GlobalVariable(*M, Type::getInt32Ty(*Ctx), false,
    822                             GlobalValue::InternalLinkage,
    823                             ConstantInt::get(Type::getInt32Ty(*Ctx),
    824                                              0xffffffff),
    825                             "__llvm_gcov_global_state_pred");
    826     GV->setUnnamedAddr(true);
    827   }
    828   return GV;
    829 }
    830 
    831 Function *GCOVProfiler::insertCounterWriteout(
    832     ArrayRef<std::pair<GlobalVariable *, MDNode *> > CountersBySP) {
    833   FunctionType *WriteoutFTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
    834   Function *WriteoutF = M->getFunction("__llvm_gcov_writeout");
    835   if (!WriteoutF)
    836     WriteoutF = Function::Create(WriteoutFTy, GlobalValue::InternalLinkage,
    837                                  "__llvm_gcov_writeout", M);
    838   WriteoutF->setUnnamedAddr(true);
    839   WriteoutF->addFnAttr(Attribute::NoInline);
    840   if (Options.NoRedZone)
    841     WriteoutF->addFnAttr(Attribute::NoRedZone);
    842 
    843   BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", WriteoutF);
    844   IRBuilder<> Builder(BB);
    845 
    846   Constant *StartFile = getStartFileFunc();
    847   Constant *EmitFunction = getEmitFunctionFunc();
    848   Constant *EmitArcs = getEmitArcsFunc();
    849   Constant *SummaryInfo = getSummaryInfoFunc();
    850   Constant *EndFile = getEndFileFunc();
    851 
    852   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
    853   if (CU_Nodes) {
    854     for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
    855       auto *CU = cast<DICompileUnit>(CU_Nodes->getOperand(i));
    856       std::string FilenameGcda = mangleName(CU, "gcda");
    857       uint32_t CfgChecksum = FileChecksums.empty() ? 0 : FileChecksums[i];
    858       Builder.CreateCall(StartFile,
    859                          {Builder.CreateGlobalStringPtr(FilenameGcda),
    860                           Builder.CreateGlobalStringPtr(ReversedVersion),
    861                           Builder.getInt32(CfgChecksum)});
    862       for (unsigned j = 0, e = CountersBySP.size(); j != e; ++j) {
    863         auto *SP = cast_or_null<DISubprogram>(CountersBySP[j].second);
    864         uint32_t FuncChecksum = Funcs.empty() ? 0 : Funcs[j]->getFuncChecksum();
    865         Builder.CreateCall(
    866             EmitFunction,
    867             {Builder.getInt32(j),
    868              Options.FunctionNamesInData
    869                  ? Builder.CreateGlobalStringPtr(getFunctionName(SP))
    870                  : Constant::getNullValue(Builder.getInt8PtrTy()),
    871              Builder.getInt32(FuncChecksum),
    872              Builder.getInt8(Options.UseCfgChecksum),
    873              Builder.getInt32(CfgChecksum)});
    874 
    875         GlobalVariable *GV = CountersBySP[j].first;
    876         unsigned Arcs =
    877           cast<ArrayType>(GV->getType()->getElementType())->getNumElements();
    878         Builder.CreateCall(EmitArcs, {Builder.getInt32(Arcs),
    879                                       Builder.CreateConstGEP2_64(GV, 0, 0)});
    880       }
    881       Builder.CreateCall(SummaryInfo, {});
    882       Builder.CreateCall(EndFile, {});
    883     }
    884   }
    885 
    886   Builder.CreateRetVoid();
    887   return WriteoutF;
    888 }
    889 
    890 void GCOVProfiler::insertIndirectCounterIncrement() {
    891   Function *Fn =
    892     cast<Function>(GCOVProfiler::getIncrementIndirectCounterFunc());
    893   Fn->setUnnamedAddr(true);
    894   Fn->setLinkage(GlobalValue::InternalLinkage);
    895   Fn->addFnAttr(Attribute::NoInline);
    896   if (Options.NoRedZone)
    897     Fn->addFnAttr(Attribute::NoRedZone);
    898 
    899   // Create basic blocks for function.
    900   BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", Fn);
    901   IRBuilder<> Builder(BB);
    902 
    903   BasicBlock *PredNotNegOne = BasicBlock::Create(*Ctx, "", Fn);
    904   BasicBlock *CounterEnd = BasicBlock::Create(*Ctx, "", Fn);
    905   BasicBlock *Exit = BasicBlock::Create(*Ctx, "exit", Fn);
    906 
    907   // uint32_t pred = *predecessor;
    908   // if (pred == 0xffffffff) return;
    909   Argument *Arg = &*Fn->arg_begin();
    910   Arg->setName("predecessor");
    911   Value *Pred = Builder.CreateLoad(Arg, "pred");
    912   Value *Cond = Builder.CreateICmpEQ(Pred, Builder.getInt32(0xffffffff));
    913   BranchInst::Create(Exit, PredNotNegOne, Cond, BB);
    914 
    915   Builder.SetInsertPoint(PredNotNegOne);
    916 
    917   // uint64_t *counter = counters[pred];
    918   // if (!counter) return;
    919   Value *ZExtPred = Builder.CreateZExt(Pred, Builder.getInt64Ty());
    920   Arg = &*std::next(Fn->arg_begin());
    921   Arg->setName("counters");
    922   Value *GEP = Builder.CreateGEP(Type::getInt64PtrTy(*Ctx), Arg, ZExtPred);
    923   Value *Counter = Builder.CreateLoad(GEP, "counter");
    924   Cond = Builder.CreateICmpEQ(Counter,
    925                               Constant::getNullValue(
    926                                   Builder.getInt64Ty()->getPointerTo()));
    927   Builder.CreateCondBr(Cond, Exit, CounterEnd);
    928 
    929   // ++*counter;
    930   Builder.SetInsertPoint(CounterEnd);
    931   Value *Add = Builder.CreateAdd(Builder.CreateLoad(Counter),
    932                                  Builder.getInt64(1));
    933   Builder.CreateStore(Add, Counter);
    934   Builder.CreateBr(Exit);
    935 
    936   // Fill in the exit block.
    937   Builder.SetInsertPoint(Exit);
    938   Builder.CreateRetVoid();
    939 }
    940 
    941 Function *GCOVProfiler::
    942 insertFlush(ArrayRef<std::pair<GlobalVariable*, MDNode*> > CountersBySP) {
    943   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
    944   Function *FlushF = M->getFunction("__llvm_gcov_flush");
    945   if (!FlushF)
    946     FlushF = Function::Create(FTy, GlobalValue::InternalLinkage,
    947                               "__llvm_gcov_flush", M);
    948   else
    949     FlushF->setLinkage(GlobalValue::InternalLinkage);
    950   FlushF->setUnnamedAddr(true);
    951   FlushF->addFnAttr(Attribute::NoInline);
    952   if (Options.NoRedZone)
    953     FlushF->addFnAttr(Attribute::NoRedZone);
    954 
    955   BasicBlock *Entry = BasicBlock::Create(*Ctx, "entry", FlushF);
    956 
    957   // Write out the current counters.
    958   Constant *WriteoutF = M->getFunction("__llvm_gcov_writeout");
    959   assert(WriteoutF && "Need to create the writeout function first!");
    960 
    961   IRBuilder<> Builder(Entry);
    962   Builder.CreateCall(WriteoutF, {});
    963 
    964   // Zero out the counters.
    965   for (ArrayRef<std::pair<GlobalVariable *, MDNode *> >::iterator
    966          I = CountersBySP.begin(), E = CountersBySP.end();
    967        I != E; ++I) {
    968     GlobalVariable *GV = I->first;
    969     Constant *Null = Constant::getNullValue(GV->getType()->getElementType());
    970     Builder.CreateStore(Null, GV);
    971   }
    972 
    973   Type *RetTy = FlushF->getReturnType();
    974   if (RetTy == Type::getVoidTy(*Ctx))
    975     Builder.CreateRetVoid();
    976   else if (RetTy->isIntegerTy())
    977     // Used if __llvm_gcov_flush was implicitly declared.
    978     Builder.CreateRet(ConstantInt::get(RetTy, 0));
    979   else
    980     report_fatal_error("invalid return type for __llvm_gcov_flush");
    981 
    982   return FlushF;
    983 }
    984