1 //===- GCOVProfiling.cpp - Insert edge counters for gcov profiling --------===//
2 //
3 //                      The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This pass implements GCOV-style profiling. When this pass is run it emits
11 // "gcno" files next to the existing source, and instruments the code that runs
12 // to records the edges between blocks that run and emit a complementary "gcda"
13 // file on exit.
14 //
15 //===----------------------------------------------------------------------===//
16 
17 #include "llvm/Transforms/Instrumentation.h"
18 #include "llvm/ADT/DenseMap.h"
19 #include "llvm/ADT/Hashing.h"
20 #include "llvm/ADT/STLExtras.h"
21 #include "llvm/ADT/Statistic.h"
22 #include "llvm/ADT/StringExtras.h"
23 #include "llvm/ADT/StringMap.h"
24 #include "llvm/ADT/UniqueVector.h"
25 #include "llvm/IR/DebugInfo.h"
26 #include "llvm/IR/DebugLoc.h"
27 #include "llvm/IR/IRBuilder.h"
28 #include "llvm/IR/InstIterator.h"
29 #include "llvm/IR/Instructions.h"
30 #include "llvm/IR/IntrinsicInst.h"
31 #include "llvm/IR/Module.h"
32 #include "llvm/Pass.h"
33 #include "llvm/Support/CommandLine.h"
34 #include "llvm/Support/Debug.h"
35 #include "llvm/Support/FileSystem.h"
36 #include "llvm/Support/Path.h"
37 #include "llvm/Support/raw_ostream.h"
38 #include "llvm/Transforms/Utils/ModuleUtils.h"
39 #include <algorithm>
40 #include <memory>
41 #include <string>
42 #include <utility>
43 using namespace llvm;
44 
45 #define DEBUG_TYPE "insert-gcov-profiling"
46 
47 static cl::opt<std::string>
48 DefaultGCOVVersion("default-gcov-version", cl::init("402*"), cl::Hidden,
49                    cl::ValueRequired);
50 
51 GCOVOptions GCOVOptions::getDefault() {
52   GCOVOptions Options;
53   Options.EmitNotes = true;
54   Options.EmitData = true;
55   Options.UseCfgChecksum = false;
56   Options.NoRedZone = false;
57   Options.FunctionNamesInData = true;
58 
59   if (DefaultGCOVVersion.size() != 4) {
60     llvm::report_fatal_error(std::string("Invalid -default-gcov-version: ") +
61                              DefaultGCOVVersion);
62   }
63   memcpy(Options.Version, DefaultGCOVVersion.c_str(), 4);
64   return Options;
65 }
66 
67 namespace {
68   class GCOVFunction;
69 
70   class GCOVProfiler : public ModulePass {
71   public:
72     static char ID;
73     GCOVProfiler() : ModulePass(ID), Options(GCOVOptions::getDefault()) {
74       init();
75     }
76     GCOVProfiler(const GCOVOptions &Options) : ModulePass(ID), Options(Options){
77       assert((Options.EmitNotes || Options.EmitData) &&
78              "GCOVProfiler asked to do nothing?");
79       init();
80     }
81     const char *getPassName() const override {
82       return "GCOV Profiler";
83     }
84 
85   private:
86     void init() {
87       ReversedVersion[0] = Options.Version[3];
88       ReversedVersion[1] = Options.Version[2];
89       ReversedVersion[2] = Options.Version[1];
90       ReversedVersion[3] = Options.Version[0];
91       ReversedVersion[4] = '\0';
92       initializeGCOVProfilerPass(*PassRegistry::getPassRegistry());
93     }
94     bool runOnModule(Module &M) override;
95 
96     // Create the .gcno files for the Module based on DebugInfo.
97     void emitProfileNotes();
98 
99     // Modify the program to track transitions along edges and call into the
100     // profiling runtime to emit .gcda files when run.
101     bool emitProfileArcs();
102 
103     // Get pointers to the functions in the runtime library.
104     Constant *getStartFileFunc();
105     Constant *getIncrementIndirectCounterFunc();
106     Constant *getEmitFunctionFunc();
107     Constant *getEmitArcsFunc();
108     Constant *getSummaryInfoFunc();
109     Constant *getDeleteWriteoutFunctionListFunc();
110     Constant *getDeleteFlushFunctionListFunc();
111     Constant *getEndFileFunc();
112 
113     // Create or retrieve an i32 state value that is used to represent the
114     // pred block number for certain non-trivial edges.
115     GlobalVariable *getEdgeStateValue();
116 
117     // Produce a table of pointers to counters, by predecessor and successor
118     // block number.
119     GlobalVariable *buildEdgeLookupTable(Function *F,
120                                          GlobalVariable *Counter,
121                                          const UniqueVector<BasicBlock *>&Preds,
122                                          const UniqueVector<BasicBlock*>&Succs);
123 
124     // Add the function to write out all our counters to the global destructor
125     // list.
126     Function *insertCounterWriteout(ArrayRef<std::pair<GlobalVariable*,
127                                                        MDNode*> >);
128     Function *insertFlush(ArrayRef<std::pair<GlobalVariable*, MDNode*> >);
129     void insertIndirectCounterIncrement();
130 
131     std::string mangleName(DICompileUnit CU, const char *NewStem);
132 
133     GCOVOptions Options;
134 
135     // Reversed, NUL-terminated copy of Options.Version.
136     char ReversedVersion[5];
137     // Checksum, produced by hash of EdgeDestinations
138     SmallVector<uint32_t, 4> FileChecksums;
139 
140     Module *M;
141     LLVMContext *Ctx;
142     SmallVector<std::unique_ptr<GCOVFunction>, 16> Funcs;
143   };
144 }
145 
146 char GCOVProfiler::ID = 0;
147 INITIALIZE_PASS(GCOVProfiler, "insert-gcov-profiling",
148                 "Insert instrumentation for GCOV profiling", false, false)
149 
150 ModulePass *llvm::createGCOVProfilerPass(const GCOVOptions &Options) {
151   return new GCOVProfiler(Options);
152 }
153 
154 static StringRef getFunctionName(DISubprogram SP) {
155   if (!SP.getLinkageName().empty())
156     return SP.getLinkageName();
157   return SP.getName();
158 }
159 
160 namespace {
161   class GCOVRecord {
162    protected:
163     static const char *const LinesTag;
164     static const char *const FunctionTag;
165     static const char *const BlockTag;
166     static const char *const EdgeTag;
167 
168     GCOVRecord() {}
169 
170     void writeBytes(const char *Bytes, int Size) {
171       os->write(Bytes, Size);
172     }
173 
174     void write(uint32_t i) {
175       writeBytes(reinterpret_cast<char*>(&i), 4);
176     }
177 
178     // Returns the length measured in 4-byte blocks that will be used to
179     // represent this string in a GCOV file
180     static unsigned lengthOfGCOVString(StringRef s) {
181       // A GCOV string is a length, followed by a NUL, then between 0 and 3 NULs
182       // padding out to the next 4-byte word. The length is measured in 4-byte
183       // words including padding, not bytes of actual string.
184       return (s.size() / 4) + 1;
185     }
186 
187     void writeGCOVString(StringRef s) {
188       uint32_t Len = lengthOfGCOVString(s);
189       write(Len);
190       writeBytes(s.data(), s.size());
191 
192       // Write 1 to 4 bytes of NUL padding.
193       assert((unsigned)(4 - (s.size() % 4)) > 0);
194       assert((unsigned)(4 - (s.size() % 4)) <= 4);
195       writeBytes("\0\0\0\0", 4 - (s.size() % 4));
196     }
197 
198     raw_ostream *os;
199   };
200   const char *const GCOVRecord::LinesTag = "\0\0\x45\x01";
201   const char *const GCOVRecord::FunctionTag = "\0\0\0\1";
202   const char *const GCOVRecord::BlockTag = "\0\0\x41\x01";
203   const char *const GCOVRecord::EdgeTag = "\0\0\x43\x01";
204 
205   class GCOVFunction;
206   class GCOVBlock;
207 
208   // Constructed only by requesting it from a GCOVBlock, this object stores a
209   // list of line numbers and a single filename, representing lines that belong
210   // to the block.
211   class GCOVLines : public GCOVRecord {
212    public:
213     void addLine(uint32_t Line) {
214       assert(Line != 0 && "Line zero is not a valid real line number.");
215       Lines.push_back(Line);
216     }
217 
218     uint32_t length() const {
219       // Here 2 = 1 for string length + 1 for '0' id#.
220       return lengthOfGCOVString(Filename) + 2 + Lines.size();
221     }
222 
223     void writeOut() {
224       write(0);
225       writeGCOVString(Filename);
226       for (int i = 0, e = Lines.size(); i != e; ++i)
227         write(Lines[i]);
228     }
229 
230     GCOVLines(StringRef F, raw_ostream *os)
231       : Filename(F) {
232       this->os = os;
233     }
234 
235    private:
236     StringRef Filename;
237     SmallVector<uint32_t, 32> Lines;
238   };
239 
240 
241   // Represent a basic block in GCOV. Each block has a unique number in the
242   // function, number of lines belonging to each block, and a set of edges to
243   // other blocks.
244   class GCOVBlock : public GCOVRecord {
245    public:
246     GCOVLines &getFile(StringRef Filename) {
247       GCOVLines *&Lines = LinesByFile[Filename];
248       if (!Lines) {
249         Lines = new GCOVLines(Filename, os);
250       }
251       return *Lines;
252     }
253 
254     void addEdge(GCOVBlock &Successor) {
255       OutEdges.push_back(&Successor);
256     }
257 
258     void writeOut() {
259       uint32_t Len = 3;
260       SmallVector<StringMapEntry<GCOVLines *> *, 32> SortedLinesByFile;
261       for (StringMap<GCOVLines *>::iterator I = LinesByFile.begin(),
262                E = LinesByFile.end(); I != E; ++I) {
263         Len += I->second->length();
264         SortedLinesByFile.push_back(&*I);
265       }
266 
267       writeBytes(LinesTag, 4);
268       write(Len);
269       write(Number);
270 
271       std::sort(SortedLinesByFile.begin(), SortedLinesByFile.end(),
272                 [](StringMapEntry<GCOVLines *> *LHS,
273                    StringMapEntry<GCOVLines *> *RHS) {
274         return LHS->getKey() < RHS->getKey();
275       });
276       for (SmallVectorImpl<StringMapEntry<GCOVLines *> *>::iterator
277                I = SortedLinesByFile.begin(), E = SortedLinesByFile.end();
278            I != E; ++I)
279         (*I)->getValue()->writeOut();
280       write(0);
281       write(0);
282     }
283 
284     ~GCOVBlock() {
285       DeleteContainerSeconds(LinesByFile);
286     }
287 
288    private:
289     friend class GCOVFunction;
290 
291     GCOVBlock(uint32_t Number, raw_ostream *os)
292         : Number(Number) {
293       this->os = os;
294     }
295 
296     uint32_t Number;
297     StringMap<GCOVLines *> LinesByFile;
298     SmallVector<GCOVBlock *, 4> OutEdges;
299   };
300 
301   // A function has a unique identifier, a checksum (we leave as zero) and a
302   // set of blocks and a map of edges between blocks. This is the only GCOV
303   // object users can construct, the blocks and lines will be rooted here.
304   class GCOVFunction : public GCOVRecord {
305    public:
306     GCOVFunction(DISubprogram SP, raw_ostream *os, uint32_t Ident,
307                  bool UseCfgChecksum) :
308         SP(SP), Ident(Ident), UseCfgChecksum(UseCfgChecksum), CfgChecksum(0) {
309       this->os = os;
310 
311       Function *F = SP.getFunction();
312       DEBUG(dbgs() << "Function: " << getFunctionName(SP) << "\n");
313       uint32_t i = 0;
314       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
315         Blocks[BB] = new GCOVBlock(i++, os);
316       }
317       ReturnBlock = new GCOVBlock(i++, os);
318 
319       string_ostream FnNameLine;
320       FnNameLine << getFunctionName(SP) << SP.getLineNumber();
321       FuncChecksum = hash_value(FnNameLine.str());
322     }
323 
324     ~GCOVFunction() {
325       DeleteContainerSeconds(Blocks);
326       delete ReturnBlock;
327     }
328 
329     GCOVBlock &getBlock(BasicBlock *BB) {
330       return *Blocks[BB];
331     }
332 
333     GCOVBlock &getReturnBlock() {
334       return *ReturnBlock;
335     }
336 
337     std::string getEdgeDestinations() {
338       string_ostream EdgeDestinations;
339       Function *F = Blocks.begin()->first->getParent();
340       for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
341         GCOVBlock &Block = *Blocks[I];
342         for (int i = 0, e = Block.OutEdges.size(); i != e; ++i)
343           EdgeDestinations << Block.OutEdges[i]->Number;
344       }
345       return EdgeDestinations.str();
346     }
347 
348     uint32_t getFuncChecksum() {
349       return FuncChecksum;
350     }
351 
352     void setCfgChecksum(uint32_t Checksum) {
353       CfgChecksum = Checksum;
354     }
355 
356     void writeOut() {
357       writeBytes(FunctionTag, 4);
358       uint32_t BlockLen = 1 + 1 + 1 + lengthOfGCOVString(getFunctionName(SP)) +
359           1 + lengthOfGCOVString(SP.getFilename()) + 1;
360       if (UseCfgChecksum)
361         ++BlockLen;
362       write(BlockLen);
363       write(Ident);
364       write(FuncChecksum);
365       if (UseCfgChecksum)
366         write(CfgChecksum);
367       writeGCOVString(getFunctionName(SP));
368       writeGCOVString(SP.getFilename());
369       write(SP.getLineNumber());
370 
371       // Emit count of blocks.
372       writeBytes(BlockTag, 4);
373       write(Blocks.size() + 1);
374       for (int i = 0, e = Blocks.size() + 1; i != e; ++i) {
375         write(0);  // No flags on our blocks.
376       }
377       DEBUG(dbgs() << Blocks.size() << " blocks.\n");
378 
379       // Emit edges between blocks.
380       if (Blocks.empty()) return;
381       Function *F = Blocks.begin()->first->getParent();
382       for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
383         GCOVBlock &Block = *Blocks[I];
384         if (Block.OutEdges.empty()) continue;
385 
386         writeBytes(EdgeTag, 4);
387         write(Block.OutEdges.size() * 2 + 1);
388         write(Block.Number);
389         for (int i = 0, e = Block.OutEdges.size(); i != e; ++i) {
390           DEBUG(dbgs() << Block.Number << " -> " << Block.OutEdges[i]->Number
391                        << "\n");
392           write(Block.OutEdges[i]->Number);
393           write(0);  // no flags
394         }
395       }
396 
397       // Emit lines for each block.
398       for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
399         Blocks[I]->writeOut();
400       }
401     }
402 
403    private:
404     DISubprogram SP;
405     uint32_t Ident;
406     uint32_t FuncChecksum;
407     bool UseCfgChecksum;
408     uint32_t CfgChecksum;
409     DenseMap<BasicBlock *, GCOVBlock *> Blocks;
410     GCOVBlock *ReturnBlock;
411   };
412 }
413 
414 std::string GCOVProfiler::mangleName(DICompileUnit CU, const char *NewStem) {
415   if (NamedMDNode *GCov = M->getNamedMetadata("llvm.gcov")) {
416     for (int i = 0, e = GCov->getNumOperands(); i != e; ++i) {
417       MDNode *N = GCov->getOperand(i);
418       if (N->getNumOperands() != 2) continue;
419       MDString *GCovFile = dyn_cast<MDString>(N->getOperand(0));
420       MDNode *CompileUnit = dyn_cast<MDNode>(N->getOperand(1));
421       if (!GCovFile || !CompileUnit) continue;
422       if (CompileUnit == CU) {
423         SmallString<128> Filename = GCovFile->getString();
424         sys::path::replace_extension(Filename, NewStem);
425         return Filename.str();
426       }
427     }
428   }
429 
430   SmallString<128> Filename = CU.getFilename();
431   sys::path::replace_extension(Filename, NewStem);
432   StringRef FName = sys::path::filename(Filename);
433   SmallString<128> CurPath;
434   if (sys::fs::current_path(CurPath)) return FName;
435   sys::path::append(CurPath, FName.str());
436   return CurPath.str();
437 }
438 
439 bool GCOVProfiler::runOnModule(Module &M) {
440   this->M = &M;
441   Ctx = &M.getContext();
442 
443   if (Options.EmitNotes) emitProfileNotes();
444   if (Options.EmitData) return emitProfileArcs();
445   return false;
446 }
447 
448 static bool functionHasLines(Function *F) {
449   // Check whether this function actually has any source lines. Not only
450   // do these waste space, they also can crash gcov.
451   for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
452     for (BasicBlock::iterator I = BB->begin(), IE = BB->end();
453          I != IE; ++I) {
454       // Debug intrinsic locations correspond to the location of the
455       // declaration, not necessarily any statements or expressions.
456       if (isa<DbgInfoIntrinsic>(I)) continue;
457 
458       const DebugLoc &Loc = I->getDebugLoc();
459       if (Loc.isUnknown()) continue;
460 
461       // Artificial lines such as calls to the global constructors.
462       if (Loc.getLine() == 0) continue;
463 
464       return true;
465     }
466   }
467   return false;
468 }
469 
470 void GCOVProfiler::emitProfileNotes() {
471   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
472   if (!CU_Nodes) return;
473 
474   for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
475     // Each compile unit gets its own .gcno file. This means that whether we run
476     // this pass over the original .o's as they're produced, or run it after
477     // LTO, we'll generate the same .gcno files.
478 
479     DICompileUnit CU(CU_Nodes->getOperand(i));
480     std::string ErrorInfo;
481     raw_fd_ostream out(mangleName(CU, "gcno").c_str(), ErrorInfo,
482                        sys::fs::F_None);
483     std::string EdgeDestinations;
484 
485     DIArray SPs = CU.getSubprograms();
486     for (unsigned i = 0, e = SPs.getNumElements(); i != e; ++i) {
487       DISubprogram SP(SPs.getElement(i));
488       assert((!SP || SP.isSubprogram()) &&
489         "A MDNode in subprograms of a CU should be null or a DISubprogram.");
490       if (!SP)
491         continue;
492 
493       Function *F = SP.getFunction();
494       if (!F) continue;
495       if (!functionHasLines(F)) continue;
496 
497       // gcov expects every function to start with an entry block that has a
498       // single successor, so split the entry block to make sure of that.
499       BasicBlock &EntryBlock = F->getEntryBlock();
500       BasicBlock::iterator It = EntryBlock.begin();
501       while (isa<AllocaInst>(*It) || isa<DbgInfoIntrinsic>(*It))
502         ++It;
503       EntryBlock.splitBasicBlock(It);
504 
505       Funcs.push_back(
506           make_unique<GCOVFunction>(SP, &out, i, Options.UseCfgChecksum));
507       GCOVFunction &Func = *Funcs.back();
508 
509       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
510         GCOVBlock &Block = Func.getBlock(BB);
511         TerminatorInst *TI = BB->getTerminator();
512         if (int successors = TI->getNumSuccessors()) {
513           for (int i = 0; i != successors; ++i) {
514             Block.addEdge(Func.getBlock(TI->getSuccessor(i)));
515           }
516         } else if (isa<ReturnInst>(TI)) {
517           Block.addEdge(Func.getReturnBlock());
518         }
519 
520         uint32_t Line = 0;
521         for (BasicBlock::iterator I = BB->begin(), IE = BB->end();
522              I != IE; ++I) {
523           // Debug intrinsic locations correspond to the location of the
524           // declaration, not necessarily any statements or expressions.
525           if (isa<DbgInfoIntrinsic>(I)) continue;
526 
527           const DebugLoc &Loc = I->getDebugLoc();
528           if (Loc.isUnknown()) continue;
529 
530           // Artificial lines such as calls to the global constructors.
531           if (Loc.getLine() == 0) continue;
532 
533           if (Line == Loc.getLine()) continue;
534           Line = Loc.getLine();
535           if (SP != getDISubprogram(Loc.getScope(*Ctx))) continue;
536 
537           GCOVLines &Lines = Block.getFile(SP.getFilename());
538           Lines.addLine(Loc.getLine());
539         }
540       }
541       EdgeDestinations += Func.getEdgeDestinations();
542     }
543 
544     FileChecksums.push_back(hash_value(EdgeDestinations));
545     out.write("oncg", 4);
546     out.write(ReversedVersion, 4);
547     out.write(reinterpret_cast<char*>(&FileChecksums.back()), 4);
548 
549     for (auto &Func : Funcs) {
550       Func->setCfgChecksum(FileChecksums.back());
551       Func->writeOut();
552     }
553 
554     out.write("\0\0\0\0\0\0\0\0", 8);  // EOF
555     out.close();
556   }
557 }
558 
559 bool GCOVProfiler::emitProfileArcs() {
560   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
561   if (!CU_Nodes) return false;
562 
563   bool Result = false;
564   bool InsertIndCounterIncrCode = false;
565   for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
566     DICompileUnit CU(CU_Nodes->getOperand(i));
567     DIArray SPs = CU.getSubprograms();
568     SmallVector<std::pair<GlobalVariable *, MDNode *>, 8> CountersBySP;
569     for (unsigned i = 0, e = SPs.getNumElements(); i != e; ++i) {
570       DISubprogram SP(SPs.getElement(i));
571       assert((!SP || SP.isSubprogram()) &&
572         "A MDNode in subprograms of a CU should be null or a DISubprogram.");
573       if (!SP)
574         continue;
575       Function *F = SP.getFunction();
576       if (!F) continue;
577       if (!functionHasLines(F)) continue;
578       if (!Result) Result = true;
579       unsigned Edges = 0;
580       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
581         TerminatorInst *TI = BB->getTerminator();
582         if (isa<ReturnInst>(TI))
583           ++Edges;
584         else
585           Edges += TI->getNumSuccessors();
586       }
587 
588       ArrayType *CounterTy =
589         ArrayType::get(Type::getInt64Ty(*Ctx), Edges);
590       GlobalVariable *Counters =
591         new GlobalVariable(*M, CounterTy, false,
592                            GlobalValue::InternalLinkage,
593                            Constant::getNullValue(CounterTy),
594                            "__llvm_gcov_ctr");
595       CountersBySP.push_back(std::make_pair(Counters, (MDNode*)SP));
596 
597       UniqueVector<BasicBlock *> ComplexEdgePreds;
598       UniqueVector<BasicBlock *> ComplexEdgeSuccs;
599 
600       unsigned Edge = 0;
601       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
602         TerminatorInst *TI = BB->getTerminator();
603         int Successors = isa<ReturnInst>(TI) ? 1 : TI->getNumSuccessors();
604         if (Successors) {
605           if (Successors == 1) {
606             IRBuilder<> Builder(BB->getFirstInsertionPt());
607             Value *Counter = Builder.CreateConstInBoundsGEP2_64(Counters, 0,
608                                                                 Edge);
609             Value *Count = Builder.CreateLoad(Counter);
610             Count = Builder.CreateAdd(Count, Builder.getInt64(1));
611             Builder.CreateStore(Count, Counter);
612           } else if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
613             IRBuilder<> Builder(BI);
614             Value *Sel = Builder.CreateSelect(BI->getCondition(),
615                                               Builder.getInt64(Edge),
616                                               Builder.getInt64(Edge + 1));
617             SmallVector<Value *, 2> Idx;
618             Idx.push_back(Builder.getInt64(0));
619             Idx.push_back(Sel);
620             Value *Counter = Builder.CreateInBoundsGEP(Counters, Idx);
621             Value *Count = Builder.CreateLoad(Counter);
622             Count = Builder.CreateAdd(Count, Builder.getInt64(1));
623             Builder.CreateStore(Count, Counter);
624           } else {
625             ComplexEdgePreds.insert(BB);
626             for (int i = 0; i != Successors; ++i)
627               ComplexEdgeSuccs.insert(TI->getSuccessor(i));
628           }
629 
630           Edge += Successors;
631         }
632       }
633 
634       if (!ComplexEdgePreds.empty()) {
635         GlobalVariable *EdgeTable =
636           buildEdgeLookupTable(F, Counters,
637                                ComplexEdgePreds, ComplexEdgeSuccs);
638         GlobalVariable *EdgeState = getEdgeStateValue();
639 
640         for (int i = 0, e = ComplexEdgePreds.size(); i != e; ++i) {
641           IRBuilder<> Builder(ComplexEdgePreds[i + 1]->getFirstInsertionPt());
642           Builder.CreateStore(Builder.getInt32(i), EdgeState);
643         }
644 
645         for (int i = 0, e = ComplexEdgeSuccs.size(); i != e; ++i) {
646           // Call runtime to perform increment.
647           IRBuilder<> Builder(ComplexEdgeSuccs[i+1]->getFirstInsertionPt());
648           Value *CounterPtrArray =
649             Builder.CreateConstInBoundsGEP2_64(EdgeTable, 0,
650                                                i * ComplexEdgePreds.size());
651 
652           // Build code to increment the counter.
653           InsertIndCounterIncrCode = true;
654           Builder.CreateCall2(getIncrementIndirectCounterFunc(),
655                               EdgeState, CounterPtrArray);
656         }
657       }
658     }
659 
660     Function *WriteoutF = insertCounterWriteout(CountersBySP);
661     Function *FlushF = insertFlush(CountersBySP);
662 
663     // Create a small bit of code that registers the "__llvm_gcov_writeout" to
664     // be executed at exit and the "__llvm_gcov_flush" function to be executed
665     // when "__gcov_flush" is called.
666     FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
667     Function *F = Function::Create(FTy, GlobalValue::InternalLinkage,
668                                    "__llvm_gcov_init", M);
669     F->setUnnamedAddr(true);
670     F->setLinkage(GlobalValue::InternalLinkage);
671     F->addFnAttr(Attribute::NoInline);
672     if (Options.NoRedZone)
673       F->addFnAttr(Attribute::NoRedZone);
674 
675     BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", F);
676     IRBuilder<> Builder(BB);
677 
678     FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
679     Type *Params[] = {
680       PointerType::get(FTy, 0),
681       PointerType::get(FTy, 0)
682     };
683     FTy = FunctionType::get(Builder.getVoidTy(), Params, false);
684 
685     // Initialize the environment and register the local writeout and flush
686     // functions.
687     Constant *GCOVInit = M->getOrInsertFunction("llvm_gcov_init", FTy);
688     Builder.CreateCall2(GCOVInit, WriteoutF, FlushF);
689     Builder.CreateRetVoid();
690 
691     appendToGlobalCtors(*M, F, 0);
692   }
693 
694   if (InsertIndCounterIncrCode)
695     insertIndirectCounterIncrement();
696 
697   return Result;
698 }
699 
700 // All edges with successors that aren't branches are "complex", because it
701 // requires complex logic to pick which counter to update.
702 GlobalVariable *GCOVProfiler::buildEdgeLookupTable(
703     Function *F,
704     GlobalVariable *Counters,
705     const UniqueVector<BasicBlock *> &Preds,
706     const UniqueVector<BasicBlock *> &Succs) {
707   // TODO: support invoke, threads. We rely on the fact that nothing can modify
708   // the whole-Module pred edge# between the time we set it and the time we next
709   // read it. Threads and invoke make this untrue.
710 
711   // emit [(succs * preds) x i64*], logically [succ x [pred x i64*]].
712   size_t TableSize = Succs.size() * Preds.size();
713   Type *Int64PtrTy = Type::getInt64PtrTy(*Ctx);
714   ArrayType *EdgeTableTy = ArrayType::get(Int64PtrTy, TableSize);
715 
716   std::unique_ptr<Constant * []> EdgeTable(new Constant *[TableSize]);
717   Constant *NullValue = Constant::getNullValue(Int64PtrTy);
718   for (size_t i = 0; i != TableSize; ++i)
719     EdgeTable[i] = NullValue;
720 
721   unsigned Edge = 0;
722   for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
723     TerminatorInst *TI = BB->getTerminator();
724     int Successors = isa<ReturnInst>(TI) ? 1 : TI->getNumSuccessors();
725     if (Successors > 1 && !isa<BranchInst>(TI) && !isa<ReturnInst>(TI)) {
726       for (int i = 0; i != Successors; ++i) {
727         BasicBlock *Succ = TI->getSuccessor(i);
728         IRBuilder<> Builder(Succ);
729         Value *Counter = Builder.CreateConstInBoundsGEP2_64(Counters, 0,
730                                                             Edge + i);
731         EdgeTable[((Succs.idFor(Succ)-1) * Preds.size()) +
732                   (Preds.idFor(BB)-1)] = cast<Constant>(Counter);
733       }
734     }
735     Edge += Successors;
736   }
737 
738   ArrayRef<Constant*> V(&EdgeTable[0], TableSize);
739   GlobalVariable *EdgeTableGV =
740       new GlobalVariable(
741           *M, EdgeTableTy, true, GlobalValue::InternalLinkage,
742           ConstantArray::get(EdgeTableTy, V),
743           "__llvm_gcda_edge_table");
744   EdgeTableGV->setUnnamedAddr(true);
745   return EdgeTableGV;
746 }
747 
748 Constant *GCOVProfiler::getStartFileFunc() {
749   Type *Args[] = {
750     Type::getInt8PtrTy(*Ctx),  // const char *orig_filename
751     Type::getInt8PtrTy(*Ctx),  // const char version[4]
752     Type::getInt32Ty(*Ctx),    // uint32_t checksum
753   };
754   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
755   return M->getOrInsertFunction("llvm_gcda_start_file", FTy);
756 }
757 
758 Constant *GCOVProfiler::getIncrementIndirectCounterFunc() {
759   Type *Int32Ty = Type::getInt32Ty(*Ctx);
760   Type *Int64Ty = Type::getInt64Ty(*Ctx);
761   Type *Args[] = {
762     Int32Ty->getPointerTo(),                // uint32_t *predecessor
763     Int64Ty->getPointerTo()->getPointerTo() // uint64_t **counters
764   };
765   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
766   return M->getOrInsertFunction("__llvm_gcov_indirect_counter_increment", FTy);
767 }
768 
769 Constant *GCOVProfiler::getEmitFunctionFunc() {
770   Type *Args[] = {
771     Type::getInt32Ty(*Ctx),    // uint32_t ident
772     Type::getInt8PtrTy(*Ctx),  // const char *function_name
773     Type::getInt32Ty(*Ctx),    // uint32_t func_checksum
774     Type::getInt8Ty(*Ctx),     // uint8_t use_extra_checksum
775     Type::getInt32Ty(*Ctx),    // uint32_t cfg_checksum
776   };
777   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
778   return M->getOrInsertFunction("llvm_gcda_emit_function", FTy);
779 }
780 
781 Constant *GCOVProfiler::getEmitArcsFunc() {
782   Type *Args[] = {
783     Type::getInt32Ty(*Ctx),     // uint32_t num_counters
784     Type::getInt64PtrTy(*Ctx),  // uint64_t *counters
785   };
786   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
787   return M->getOrInsertFunction("llvm_gcda_emit_arcs", FTy);
788 }
789 
790 Constant *GCOVProfiler::getSummaryInfoFunc() {
791   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
792   return M->getOrInsertFunction("llvm_gcda_summary_info", FTy);
793 }
794 
795 Constant *GCOVProfiler::getDeleteWriteoutFunctionListFunc() {
796   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
797   return M->getOrInsertFunction("llvm_delete_writeout_function_list", FTy);
798 }
799 
800 Constant *GCOVProfiler::getDeleteFlushFunctionListFunc() {
801   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
802   return M->getOrInsertFunction("llvm_delete_flush_function_list", FTy);
803 }
804 
805 Constant *GCOVProfiler::getEndFileFunc() {
806   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
807   return M->getOrInsertFunction("llvm_gcda_end_file", FTy);
808 }
809 
810 GlobalVariable *GCOVProfiler::getEdgeStateValue() {
811   GlobalVariable *GV = M->getGlobalVariable("__llvm_gcov_global_state_pred");
812   if (!GV) {
813     GV = new GlobalVariable(*M, Type::getInt32Ty(*Ctx), false,
814                             GlobalValue::InternalLinkage,
815                             ConstantInt::get(Type::getInt32Ty(*Ctx),
816                                              0xffffffff),
817                             "__llvm_gcov_global_state_pred");
818     GV->setUnnamedAddr(true);
819   }
820   return GV;
821 }
822 
823 Function *GCOVProfiler::insertCounterWriteout(
824     ArrayRef<std::pair<GlobalVariable *, MDNode *> > CountersBySP) {
825   FunctionType *WriteoutFTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
826   Function *WriteoutF = M->getFunction("__llvm_gcov_writeout");
827   if (!WriteoutF)
828     WriteoutF = Function::Create(WriteoutFTy, GlobalValue::InternalLinkage,
829                                  "__llvm_gcov_writeout", M);
830   WriteoutF->setUnnamedAddr(true);
831   WriteoutF->addFnAttr(Attribute::NoInline);
832   if (Options.NoRedZone)
833     WriteoutF->addFnAttr(Attribute::NoRedZone);
834 
835   BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", WriteoutF);
836   IRBuilder<> Builder(BB);
837 
838   Constant *StartFile = getStartFileFunc();
839   Constant *EmitFunction = getEmitFunctionFunc();
840   Constant *EmitArcs = getEmitArcsFunc();
841   Constant *SummaryInfo = getSummaryInfoFunc();
842   Constant *EndFile = getEndFileFunc();
843 
844   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
845   if (CU_Nodes) {
846     for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
847       DICompileUnit CU(CU_Nodes->getOperand(i));
848       std::string FilenameGcda = mangleName(CU, "gcda");
849       uint32_t CfgChecksum = FileChecksums.empty() ? 0 : FileChecksums[i];
850       Builder.CreateCall3(StartFile,
851                           Builder.CreateGlobalStringPtr(FilenameGcda),
852                           Builder.CreateGlobalStringPtr(ReversedVersion),
853                           Builder.getInt32(CfgChecksum));
854       for (unsigned j = 0, e = CountersBySP.size(); j != e; ++j) {
855         DISubprogram SP(CountersBySP[j].second);
856         uint32_t FuncChecksum = Funcs.empty() ? 0 : Funcs[j]->getFuncChecksum();
857         Builder.CreateCall5(
858             EmitFunction, Builder.getInt32(j),
859             Options.FunctionNamesInData ?
860               Builder.CreateGlobalStringPtr(getFunctionName(SP)) :
861               Constant::getNullValue(Builder.getInt8PtrTy()),
862             Builder.getInt32(FuncChecksum),
863             Builder.getInt8(Options.UseCfgChecksum),
864             Builder.getInt32(CfgChecksum));
865 
866         GlobalVariable *GV = CountersBySP[j].first;
867         unsigned Arcs =
868           cast<ArrayType>(GV->getType()->getElementType())->getNumElements();
869         Builder.CreateCall2(EmitArcs,
870                             Builder.getInt32(Arcs),
871                             Builder.CreateConstGEP2_64(GV, 0, 0));
872       }
873       Builder.CreateCall(SummaryInfo);
874       Builder.CreateCall(EndFile);
875     }
876   }
877 
878   Builder.CreateRetVoid();
879   return WriteoutF;
880 }
881 
882 void GCOVProfiler::insertIndirectCounterIncrement() {
883   Function *Fn =
884     cast<Function>(GCOVProfiler::getIncrementIndirectCounterFunc());
885   Fn->setUnnamedAddr(true);
886   Fn->setLinkage(GlobalValue::InternalLinkage);
887   Fn->addFnAttr(Attribute::NoInline);
888   if (Options.NoRedZone)
889     Fn->addFnAttr(Attribute::NoRedZone);
890 
891   // Create basic blocks for function.
892   BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", Fn);
893   IRBuilder<> Builder(BB);
894 
895   BasicBlock *PredNotNegOne = BasicBlock::Create(*Ctx, "", Fn);
896   BasicBlock *CounterEnd = BasicBlock::Create(*Ctx, "", Fn);
897   BasicBlock *Exit = BasicBlock::Create(*Ctx, "exit", Fn);
898 
899   // uint32_t pred = *predecessor;
900   // if (pred == 0xffffffff) return;
901   Argument *Arg = Fn->arg_begin();
902   Arg->setName("predecessor");
903   Value *Pred = Builder.CreateLoad(Arg, "pred");
904   Value *Cond = Builder.CreateICmpEQ(Pred, Builder.getInt32(0xffffffff));
905   BranchInst::Create(Exit, PredNotNegOne, Cond, BB);
906 
907   Builder.SetInsertPoint(PredNotNegOne);
908 
909   // uint64_t *counter = counters[pred];
910   // if (!counter) return;
911   Value *ZExtPred = Builder.CreateZExt(Pred, Builder.getInt64Ty());
912   Arg = std::next(Fn->arg_begin());
913   Arg->setName("counters");
914   Value *GEP = Builder.CreateGEP(Arg, ZExtPred);
915   Value *Counter = Builder.CreateLoad(GEP, "counter");
916   Cond = Builder.CreateICmpEQ(Counter,
917                               Constant::getNullValue(
918                                   Builder.getInt64Ty()->getPointerTo()));
919   Builder.CreateCondBr(Cond, Exit, CounterEnd);
920 
921   // ++*counter;
922   Builder.SetInsertPoint(CounterEnd);
923   Value *Add = Builder.CreateAdd(Builder.CreateLoad(Counter),
924                                  Builder.getInt64(1));
925   Builder.CreateStore(Add, Counter);
926   Builder.CreateBr(Exit);
927 
928   // Fill in the exit block.
929   Builder.SetInsertPoint(Exit);
930   Builder.CreateRetVoid();
931 }
932 
933 Function *GCOVProfiler::
934 insertFlush(ArrayRef<std::pair<GlobalVariable*, MDNode*> > CountersBySP) {
935   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
936   Function *FlushF = M->getFunction("__llvm_gcov_flush");
937   if (!FlushF)
938     FlushF = Function::Create(FTy, GlobalValue::InternalLinkage,
939                               "__llvm_gcov_flush", M);
940   else
941     FlushF->setLinkage(GlobalValue::InternalLinkage);
942   FlushF->setUnnamedAddr(true);
943   FlushF->addFnAttr(Attribute::NoInline);
944   if (Options.NoRedZone)
945     FlushF->addFnAttr(Attribute::NoRedZone);
946 
947   BasicBlock *Entry = BasicBlock::Create(*Ctx, "entry", FlushF);
948 
949   // Write out the current counters.
950   Constant *WriteoutF = M->getFunction("__llvm_gcov_writeout");
951   assert(WriteoutF && "Need to create the writeout function first!");
952 
953   IRBuilder<> Builder(Entry);
954   Builder.CreateCall(WriteoutF);
955 
956   // Zero out the counters.
957   for (ArrayRef<std::pair<GlobalVariable *, MDNode *> >::iterator
958          I = CountersBySP.begin(), E = CountersBySP.end();
959        I != E; ++I) {
960     GlobalVariable *GV = I->first;
961     Constant *Null = Constant::getNullValue(GV->getType()->getElementType());
962     Builder.CreateStore(Null, GV);
963   }
964 
965   Type *RetTy = FlushF->getReturnType();
966   if (RetTy == Type::getVoidTy(*Ctx))
967     Builder.CreateRetVoid();
968   else if (RetTy->isIntegerTy())
969     // Used if __llvm_gcov_flush was implicitly declared.
970     Builder.CreateRet(ConstantInt::get(RetTy, 0));
971   else
972     report_fatal_error("invalid return type for __llvm_gcov_flush");
973 
974   return FlushF;
975 }
976