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     GCOVBlock(const GCOVBlock &RHS) : GCOVRecord(RHS), Number(RHS.Number) {
289       // Only allow copy before edges and lines have been added. After that,
290       // there are inter-block pointers (eg: edges) that won't take kindly to
291       // blocks being copied or moved around.
292       assert(LinesByFile.empty());
293       assert(OutEdges.empty());
294     }
295 
296    private:
297     friend class GCOVFunction;
298 
299     GCOVBlock(uint32_t Number, raw_ostream *os)
300         : Number(Number) {
301       this->os = os;
302     }
303 
304     uint32_t Number;
305     StringMap<GCOVLines *> LinesByFile;
306     SmallVector<GCOVBlock *, 4> OutEdges;
307   };
308 
309   // A function has a unique identifier, a checksum (we leave as zero) and a
310   // set of blocks and a map of edges between blocks. This is the only GCOV
311   // object users can construct, the blocks and lines will be rooted here.
312   class GCOVFunction : public GCOVRecord {
313    public:
314      GCOVFunction(DISubprogram SP, raw_ostream *os, uint32_t Ident,
315                   bool UseCfgChecksum)
316          : SP(SP), Ident(Ident), UseCfgChecksum(UseCfgChecksum), CfgChecksum(0),
317            ReturnBlock(1, os) {
318       this->os = os;
319 
320       Function *F = SP.getFunction();
321       DEBUG(dbgs() << "Function: " << getFunctionName(SP) << "\n");
322 
323       uint32_t i = 0;
324       for (auto &BB : *F) {
325         // Skip index 1 (0, 2, 3, 4, ...) because that's assigned to the
326         // ReturnBlock.
327         bool first = i == 0;
328         Blocks.insert(std::make_pair(&BB, GCOVBlock(i++ + !first, os)));
329       }
330 
331       std::string FunctionNameAndLine;
332       raw_string_ostream FNLOS(FunctionNameAndLine);
333       FNLOS << getFunctionName(SP) << SP.getLineNumber();
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 (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
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.getLineNumber());
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 (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
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 (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
409         getBlock(I).writeOut();
410       }
411     }
412 
413    private:
414     DISubprogram SP;
415     uint32_t Ident;
416     uint32_t FuncChecksum;
417     bool UseCfgChecksum;
418     uint32_t CfgChecksum;
419     DenseMap<BasicBlock *, GCOVBlock> Blocks;
420     GCOVBlock ReturnBlock;
421   };
422 }
423 
424 std::string GCOVProfiler::mangleName(DICompileUnit CU, 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.str());
446   return CurPath.str();
447 }
448 
449 bool GCOVProfiler::runOnModule(Module &M) {
450   this->M = &M;
451   Ctx = &M.getContext();
452 
453   if (Options.EmitNotes) emitProfileNotes();
454   if (Options.EmitData) return emitProfileArcs();
455   return false;
456 }
457 
458 static bool functionHasLines(Function *F) {
459   // Check whether this function actually has any source lines. Not only
460   // do these waste space, they also can crash gcov.
461   for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
462     for (BasicBlock::iterator I = BB->begin(), IE = BB->end();
463          I != IE; ++I) {
464       // Debug intrinsic locations correspond to the location of the
465       // declaration, not necessarily any statements or expressions.
466       if (isa<DbgInfoIntrinsic>(I)) continue;
467 
468       const DebugLoc &Loc = I->getDebugLoc();
469       if (Loc.isUnknown()) continue;
470 
471       // Artificial lines such as calls to the global constructors.
472       if (Loc.getLine() == 0) continue;
473 
474       return true;
475     }
476   }
477   return false;
478 }
479 
480 void GCOVProfiler::emitProfileNotes() {
481   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
482   if (!CU_Nodes) return;
483 
484   for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
485     // Each compile unit gets its own .gcno file. This means that whether we run
486     // this pass over the original .o's as they're produced, or run it after
487     // LTO, we'll generate the same .gcno files.
488 
489     DICompileUnit CU(CU_Nodes->getOperand(i));
490     std::error_code EC;
491     raw_fd_ostream out(mangleName(CU, "gcno"), EC, sys::fs::F_None);
492     std::string EdgeDestinations;
493 
494     DIArray SPs = CU.getSubprograms();
495     unsigned FunctionIdent = 0;
496     for (unsigned i = 0, e = SPs.getNumElements(); i != e; ++i) {
497       DISubprogram SP(SPs.getElement(i));
498       assert((!SP || SP.isSubprogram()) &&
499         "A MDNode in subprograms of a CU should be null or a DISubprogram.");
500       if (!SP)
501         continue;
502 
503       Function *F = SP.getFunction();
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, &out, FunctionIdent++,
516                                                 Options.UseCfgChecksum));
517       GCOVFunction &Func = *Funcs.back();
518 
519       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
520         GCOVBlock &Block = Func.getBlock(BB);
521         TerminatorInst *TI = BB->getTerminator();
522         if (int successors = TI->getNumSuccessors()) {
523           for (int i = 0; i != successors; ++i) {
524             Block.addEdge(Func.getBlock(TI->getSuccessor(i)));
525           }
526         } else if (isa<ReturnInst>(TI)) {
527           Block.addEdge(Func.getReturnBlock());
528         }
529 
530         uint32_t Line = 0;
531         for (BasicBlock::iterator I = BB->begin(), IE = BB->end();
532              I != IE; ++I) {
533           // Debug intrinsic locations correspond to the location of the
534           // declaration, not necessarily any statements or expressions.
535           if (isa<DbgInfoIntrinsic>(I)) continue;
536 
537           const DebugLoc &Loc = I->getDebugLoc();
538           if (Loc.isUnknown()) continue;
539 
540           // Artificial lines such as calls to the global constructors.
541           if (Loc.getLine() == 0) continue;
542 
543           if (Line == Loc.getLine()) continue;
544           Line = Loc.getLine();
545           if (SP != getDISubprogram(Loc.getScope(*Ctx))) continue;
546 
547           GCOVLines &Lines = Block.getFile(SP.getFilename());
548           Lines.addLine(Loc.getLine());
549         }
550       }
551       EdgeDestinations += Func.getEdgeDestinations();
552     }
553 
554     FileChecksums.push_back(hash_value(EdgeDestinations));
555     out.write("oncg", 4);
556     out.write(ReversedVersion, 4);
557     out.write(reinterpret_cast<char*>(&FileChecksums.back()), 4);
558 
559     for (auto &Func : Funcs) {
560       Func->setCfgChecksum(FileChecksums.back());
561       Func->writeOut();
562     }
563 
564     out.write("\0\0\0\0\0\0\0\0", 8);  // EOF
565     out.close();
566   }
567 }
568 
569 bool GCOVProfiler::emitProfileArcs() {
570   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
571   if (!CU_Nodes) return false;
572 
573   bool Result = false;
574   bool InsertIndCounterIncrCode = false;
575   for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
576     DICompileUnit CU(CU_Nodes->getOperand(i));
577     DIArray SPs = CU.getSubprograms();
578     SmallVector<std::pair<GlobalVariable *, MDNode *>, 8> CountersBySP;
579     for (unsigned i = 0, e = SPs.getNumElements(); i != e; ++i) {
580       DISubprogram SP(SPs.getElement(i));
581       assert((!SP || SP.isSubprogram()) &&
582         "A MDNode in subprograms of a CU should be null or a DISubprogram.");
583       if (!SP)
584         continue;
585       Function *F = SP.getFunction();
586       if (!F) continue;
587       if (!functionHasLines(F)) continue;
588       if (!Result) Result = true;
589       unsigned Edges = 0;
590       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
591         TerminatorInst *TI = BB->getTerminator();
592         if (isa<ReturnInst>(TI))
593           ++Edges;
594         else
595           Edges += TI->getNumSuccessors();
596       }
597 
598       ArrayType *CounterTy =
599         ArrayType::get(Type::getInt64Ty(*Ctx), Edges);
600       GlobalVariable *Counters =
601         new GlobalVariable(*M, CounterTy, false,
602                            GlobalValue::InternalLinkage,
603                            Constant::getNullValue(CounterTy),
604                            "__llvm_gcov_ctr");
605       CountersBySP.push_back(std::make_pair(Counters, (MDNode*)SP));
606 
607       UniqueVector<BasicBlock *> ComplexEdgePreds;
608       UniqueVector<BasicBlock *> ComplexEdgeSuccs;
609 
610       unsigned Edge = 0;
611       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
612         TerminatorInst *TI = BB->getTerminator();
613         int Successors = isa<ReturnInst>(TI) ? 1 : TI->getNumSuccessors();
614         if (Successors) {
615           if (Successors == 1) {
616             IRBuilder<> Builder(BB->getFirstInsertionPt());
617             Value *Counter = Builder.CreateConstInBoundsGEP2_64(Counters, 0,
618                                                                 Edge);
619             Value *Count = Builder.CreateLoad(Counter);
620             Count = Builder.CreateAdd(Count, Builder.getInt64(1));
621             Builder.CreateStore(Count, Counter);
622           } else if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
623             IRBuilder<> Builder(BI);
624             Value *Sel = Builder.CreateSelect(BI->getCondition(),
625                                               Builder.getInt64(Edge),
626                                               Builder.getInt64(Edge + 1));
627             SmallVector<Value *, 2> Idx;
628             Idx.push_back(Builder.getInt64(0));
629             Idx.push_back(Sel);
630             Value *Counter = Builder.CreateInBoundsGEP(Counters, Idx);
631             Value *Count = Builder.CreateLoad(Counter);
632             Count = Builder.CreateAdd(Count, Builder.getInt64(1));
633             Builder.CreateStore(Count, Counter);
634           } else {
635             ComplexEdgePreds.insert(BB);
636             for (int i = 0; i != Successors; ++i)
637               ComplexEdgeSuccs.insert(TI->getSuccessor(i));
638           }
639 
640           Edge += Successors;
641         }
642       }
643 
644       if (!ComplexEdgePreds.empty()) {
645         GlobalVariable *EdgeTable =
646           buildEdgeLookupTable(F, Counters,
647                                ComplexEdgePreds, ComplexEdgeSuccs);
648         GlobalVariable *EdgeState = getEdgeStateValue();
649 
650         for (int i = 0, e = ComplexEdgePreds.size(); i != e; ++i) {
651           IRBuilder<> Builder(ComplexEdgePreds[i + 1]->getFirstInsertionPt());
652           Builder.CreateStore(Builder.getInt32(i), EdgeState);
653         }
654 
655         for (int i = 0, e = ComplexEdgeSuccs.size(); i != e; ++i) {
656           // Call runtime to perform increment.
657           IRBuilder<> Builder(ComplexEdgeSuccs[i+1]->getFirstInsertionPt());
658           Value *CounterPtrArray =
659             Builder.CreateConstInBoundsGEP2_64(EdgeTable, 0,
660                                                i * ComplexEdgePreds.size());
661 
662           // Build code to increment the counter.
663           InsertIndCounterIncrCode = true;
664           Builder.CreateCall2(getIncrementIndirectCounterFunc(),
665                               EdgeState, CounterPtrArray);
666         }
667       }
668     }
669 
670     Function *WriteoutF = insertCounterWriteout(CountersBySP);
671     Function *FlushF = insertFlush(CountersBySP);
672 
673     // Create a small bit of code that registers the "__llvm_gcov_writeout" to
674     // be executed at exit and the "__llvm_gcov_flush" function to be executed
675     // when "__gcov_flush" is called.
676     FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
677     Function *F = Function::Create(FTy, GlobalValue::InternalLinkage,
678                                    "__llvm_gcov_init", M);
679     F->setUnnamedAddr(true);
680     F->setLinkage(GlobalValue::InternalLinkage);
681     F->addFnAttr(Attribute::NoInline);
682     if (Options.NoRedZone)
683       F->addFnAttr(Attribute::NoRedZone);
684 
685     BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", F);
686     IRBuilder<> Builder(BB);
687 
688     FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
689     Type *Params[] = {
690       PointerType::get(FTy, 0),
691       PointerType::get(FTy, 0)
692     };
693     FTy = FunctionType::get(Builder.getVoidTy(), Params, false);
694 
695     // Initialize the environment and register the local writeout and flush
696     // functions.
697     Constant *GCOVInit = M->getOrInsertFunction("llvm_gcov_init", FTy);
698     Builder.CreateCall2(GCOVInit, WriteoutF, FlushF);
699     Builder.CreateRetVoid();
700 
701     appendToGlobalCtors(*M, F, 0);
702   }
703 
704   if (InsertIndCounterIncrCode)
705     insertIndirectCounterIncrement();
706 
707   return Result;
708 }
709 
710 // All edges with successors that aren't branches are "complex", because it
711 // requires complex logic to pick which counter to update.
712 GlobalVariable *GCOVProfiler::buildEdgeLookupTable(
713     Function *F,
714     GlobalVariable *Counters,
715     const UniqueVector<BasicBlock *> &Preds,
716     const UniqueVector<BasicBlock *> &Succs) {
717   // TODO: support invoke, threads. We rely on the fact that nothing can modify
718   // the whole-Module pred edge# between the time we set it and the time we next
719   // read it. Threads and invoke make this untrue.
720 
721   // emit [(succs * preds) x i64*], logically [succ x [pred x i64*]].
722   size_t TableSize = Succs.size() * Preds.size();
723   Type *Int64PtrTy = Type::getInt64PtrTy(*Ctx);
724   ArrayType *EdgeTableTy = ArrayType::get(Int64PtrTy, TableSize);
725 
726   std::unique_ptr<Constant * []> EdgeTable(new Constant *[TableSize]);
727   Constant *NullValue = Constant::getNullValue(Int64PtrTy);
728   for (size_t i = 0; i != TableSize; ++i)
729     EdgeTable[i] = NullValue;
730 
731   unsigned Edge = 0;
732   for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
733     TerminatorInst *TI = BB->getTerminator();
734     int Successors = isa<ReturnInst>(TI) ? 1 : TI->getNumSuccessors();
735     if (Successors > 1 && !isa<BranchInst>(TI) && !isa<ReturnInst>(TI)) {
736       for (int i = 0; i != Successors; ++i) {
737         BasicBlock *Succ = TI->getSuccessor(i);
738         IRBuilder<> Builder(Succ);
739         Value *Counter = Builder.CreateConstInBoundsGEP2_64(Counters, 0,
740                                                             Edge + i);
741         EdgeTable[((Succs.idFor(Succ)-1) * Preds.size()) +
742                   (Preds.idFor(BB)-1)] = cast<Constant>(Counter);
743       }
744     }
745     Edge += Successors;
746   }
747 
748   GlobalVariable *EdgeTableGV =
749       new GlobalVariable(
750           *M, EdgeTableTy, true, GlobalValue::InternalLinkage,
751           ConstantArray::get(EdgeTableTy,
752                              makeArrayRef(&EdgeTable[0],TableSize)),
753           "__llvm_gcda_edge_table");
754   EdgeTableGV->setUnnamedAddr(true);
755   return EdgeTableGV;
756 }
757 
758 Constant *GCOVProfiler::getStartFileFunc() {
759   Type *Args[] = {
760     Type::getInt8PtrTy(*Ctx),  // const char *orig_filename
761     Type::getInt8PtrTy(*Ctx),  // const char version[4]
762     Type::getInt32Ty(*Ctx),    // uint32_t checksum
763   };
764   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
765   return M->getOrInsertFunction("llvm_gcda_start_file", FTy);
766 }
767 
768 Constant *GCOVProfiler::getIncrementIndirectCounterFunc() {
769   Type *Int32Ty = Type::getInt32Ty(*Ctx);
770   Type *Int64Ty = Type::getInt64Ty(*Ctx);
771   Type *Args[] = {
772     Int32Ty->getPointerTo(),                // uint32_t *predecessor
773     Int64Ty->getPointerTo()->getPointerTo() // uint64_t **counters
774   };
775   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
776   return M->getOrInsertFunction("__llvm_gcov_indirect_counter_increment", FTy);
777 }
778 
779 Constant *GCOVProfiler::getEmitFunctionFunc() {
780   Type *Args[] = {
781     Type::getInt32Ty(*Ctx),    // uint32_t ident
782     Type::getInt8PtrTy(*Ctx),  // const char *function_name
783     Type::getInt32Ty(*Ctx),    // uint32_t func_checksum
784     Type::getInt8Ty(*Ctx),     // uint8_t use_extra_checksum
785     Type::getInt32Ty(*Ctx),    // uint32_t cfg_checksum
786   };
787   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
788   return M->getOrInsertFunction("llvm_gcda_emit_function", FTy);
789 }
790 
791 Constant *GCOVProfiler::getEmitArcsFunc() {
792   Type *Args[] = {
793     Type::getInt32Ty(*Ctx),     // uint32_t num_counters
794     Type::getInt64PtrTy(*Ctx),  // uint64_t *counters
795   };
796   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
797   return M->getOrInsertFunction("llvm_gcda_emit_arcs", FTy);
798 }
799 
800 Constant *GCOVProfiler::getSummaryInfoFunc() {
801   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
802   return M->getOrInsertFunction("llvm_gcda_summary_info", FTy);
803 }
804 
805 Constant *GCOVProfiler::getDeleteWriteoutFunctionListFunc() {
806   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
807   return M->getOrInsertFunction("llvm_delete_writeout_function_list", FTy);
808 }
809 
810 Constant *GCOVProfiler::getDeleteFlushFunctionListFunc() {
811   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
812   return M->getOrInsertFunction("llvm_delete_flush_function_list", FTy);
813 }
814 
815 Constant *GCOVProfiler::getEndFileFunc() {
816   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
817   return M->getOrInsertFunction("llvm_gcda_end_file", FTy);
818 }
819 
820 GlobalVariable *GCOVProfiler::getEdgeStateValue() {
821   GlobalVariable *GV = M->getGlobalVariable("__llvm_gcov_global_state_pred");
822   if (!GV) {
823     GV = new GlobalVariable(*M, Type::getInt32Ty(*Ctx), false,
824                             GlobalValue::InternalLinkage,
825                             ConstantInt::get(Type::getInt32Ty(*Ctx),
826                                              0xffffffff),
827                             "__llvm_gcov_global_state_pred");
828     GV->setUnnamedAddr(true);
829   }
830   return GV;
831 }
832 
833 Function *GCOVProfiler::insertCounterWriteout(
834     ArrayRef<std::pair<GlobalVariable *, MDNode *> > CountersBySP) {
835   FunctionType *WriteoutFTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
836   Function *WriteoutF = M->getFunction("__llvm_gcov_writeout");
837   if (!WriteoutF)
838     WriteoutF = Function::Create(WriteoutFTy, GlobalValue::InternalLinkage,
839                                  "__llvm_gcov_writeout", M);
840   WriteoutF->setUnnamedAddr(true);
841   WriteoutF->addFnAttr(Attribute::NoInline);
842   if (Options.NoRedZone)
843     WriteoutF->addFnAttr(Attribute::NoRedZone);
844 
845   BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", WriteoutF);
846   IRBuilder<> Builder(BB);
847 
848   Constant *StartFile = getStartFileFunc();
849   Constant *EmitFunction = getEmitFunctionFunc();
850   Constant *EmitArcs = getEmitArcsFunc();
851   Constant *SummaryInfo = getSummaryInfoFunc();
852   Constant *EndFile = getEndFileFunc();
853 
854   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
855   if (CU_Nodes) {
856     for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
857       DICompileUnit CU(CU_Nodes->getOperand(i));
858       std::string FilenameGcda = mangleName(CU, "gcda");
859       uint32_t CfgChecksum = FileChecksums.empty() ? 0 : FileChecksums[i];
860       Builder.CreateCall3(StartFile,
861                           Builder.CreateGlobalStringPtr(FilenameGcda),
862                           Builder.CreateGlobalStringPtr(ReversedVersion),
863                           Builder.getInt32(CfgChecksum));
864       for (unsigned j = 0, e = CountersBySP.size(); j != e; ++j) {
865         DISubprogram SP(CountersBySP[j].second);
866         uint32_t FuncChecksum = Funcs.empty() ? 0 : Funcs[j]->getFuncChecksum();
867         Builder.CreateCall5(
868             EmitFunction, Builder.getInt32(j),
869             Options.FunctionNamesInData ?
870               Builder.CreateGlobalStringPtr(getFunctionName(SP)) :
871               Constant::getNullValue(Builder.getInt8PtrTy()),
872             Builder.getInt32(FuncChecksum),
873             Builder.getInt8(Options.UseCfgChecksum),
874             Builder.getInt32(CfgChecksum));
875 
876         GlobalVariable *GV = CountersBySP[j].first;
877         unsigned Arcs =
878           cast<ArrayType>(GV->getType()->getElementType())->getNumElements();
879         Builder.CreateCall2(EmitArcs,
880                             Builder.getInt32(Arcs),
881                             Builder.CreateConstGEP2_64(GV, 0, 0));
882       }
883       Builder.CreateCall(SummaryInfo);
884       Builder.CreateCall(EndFile);
885     }
886   }
887 
888   Builder.CreateRetVoid();
889   return WriteoutF;
890 }
891 
892 void GCOVProfiler::insertIndirectCounterIncrement() {
893   Function *Fn =
894     cast<Function>(GCOVProfiler::getIncrementIndirectCounterFunc());
895   Fn->setUnnamedAddr(true);
896   Fn->setLinkage(GlobalValue::InternalLinkage);
897   Fn->addFnAttr(Attribute::NoInline);
898   if (Options.NoRedZone)
899     Fn->addFnAttr(Attribute::NoRedZone);
900 
901   // Create basic blocks for function.
902   BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", Fn);
903   IRBuilder<> Builder(BB);
904 
905   BasicBlock *PredNotNegOne = BasicBlock::Create(*Ctx, "", Fn);
906   BasicBlock *CounterEnd = BasicBlock::Create(*Ctx, "", Fn);
907   BasicBlock *Exit = BasicBlock::Create(*Ctx, "exit", Fn);
908 
909   // uint32_t pred = *predecessor;
910   // if (pred == 0xffffffff) return;
911   Argument *Arg = Fn->arg_begin();
912   Arg->setName("predecessor");
913   Value *Pred = Builder.CreateLoad(Arg, "pred");
914   Value *Cond = Builder.CreateICmpEQ(Pred, Builder.getInt32(0xffffffff));
915   BranchInst::Create(Exit, PredNotNegOne, Cond, BB);
916 
917   Builder.SetInsertPoint(PredNotNegOne);
918 
919   // uint64_t *counter = counters[pred];
920   // if (!counter) return;
921   Value *ZExtPred = Builder.CreateZExt(Pred, Builder.getInt64Ty());
922   Arg = std::next(Fn->arg_begin());
923   Arg->setName("counters");
924   Value *GEP = Builder.CreateGEP(Arg, ZExtPred);
925   Value *Counter = Builder.CreateLoad(GEP, "counter");
926   Cond = Builder.CreateICmpEQ(Counter,
927                               Constant::getNullValue(
928                                   Builder.getInt64Ty()->getPointerTo()));
929   Builder.CreateCondBr(Cond, Exit, CounterEnd);
930 
931   // ++*counter;
932   Builder.SetInsertPoint(CounterEnd);
933   Value *Add = Builder.CreateAdd(Builder.CreateLoad(Counter),
934                                  Builder.getInt64(1));
935   Builder.CreateStore(Add, Counter);
936   Builder.CreateBr(Exit);
937 
938   // Fill in the exit block.
939   Builder.SetInsertPoint(Exit);
940   Builder.CreateRetVoid();
941 }
942 
943 Function *GCOVProfiler::
944 insertFlush(ArrayRef<std::pair<GlobalVariable*, MDNode*> > CountersBySP) {
945   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
946   Function *FlushF = M->getFunction("__llvm_gcov_flush");
947   if (!FlushF)
948     FlushF = Function::Create(FTy, GlobalValue::InternalLinkage,
949                               "__llvm_gcov_flush", M);
950   else
951     FlushF->setLinkage(GlobalValue::InternalLinkage);
952   FlushF->setUnnamedAddr(true);
953   FlushF->addFnAttr(Attribute::NoInline);
954   if (Options.NoRedZone)
955     FlushF->addFnAttr(Attribute::NoRedZone);
956 
957   BasicBlock *Entry = BasicBlock::Create(*Ctx, "entry", FlushF);
958 
959   // Write out the current counters.
960   Constant *WriteoutF = M->getFunction("__llvm_gcov_writeout");
961   assert(WriteoutF && "Need to create the writeout function first!");
962 
963   IRBuilder<> Builder(Entry);
964   Builder.CreateCall(WriteoutF);
965 
966   // Zero out the counters.
967   for (ArrayRef<std::pair<GlobalVariable *, MDNode *> >::iterator
968          I = CountersBySP.begin(), E = CountersBySP.end();
969        I != E; ++I) {
970     GlobalVariable *GV = I->first;
971     Constant *Null = Constant::getNullValue(GV->getType()->getElementType());
972     Builder.CreateStore(Null, GV);
973   }
974 
975   Type *RetTy = FlushF->getReturnType();
976   if (RetTy == Type::getVoidTy(*Ctx))
977     Builder.CreateRetVoid();
978   else if (RetTy->isIntegerTy())
979     // Used if __llvm_gcov_flush was implicitly declared.
980     Builder.CreateRet(ConstantInt::get(RetTy, 0));
981   else
982     report_fatal_error("invalid return type for __llvm_gcov_flush");
983 
984   return FlushF;
985 }
986