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