1 //===- GCOVProfiling.cpp - Insert edge counters for gcov profiling --------===//
2 //
3 //                      The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This pass implements GCOV-style profiling. When this pass is run it emits
11 // "gcno" files next to the existing source, and instruments the code that runs
12 // to records the edges between blocks that run and emit a complementary "gcda"
13 // file on exit.
14 //
15 //===----------------------------------------------------------------------===//
16 
17 #include "llvm/Transforms/Instrumentation.h"
18 #include "llvm/ADT/DenseMap.h"
19 #include "llvm/ADT/Hashing.h"
20 #include "llvm/ADT/STLExtras.h"
21 #include "llvm/ADT/Statistic.h"
22 #include "llvm/ADT/StringExtras.h"
23 #include "llvm/ADT/StringMap.h"
24 #include "llvm/ADT/UniqueVector.h"
25 #include "llvm/IR/DebugInfo.h"
26 #include "llvm/IR/DebugLoc.h"
27 #include "llvm/IR/IRBuilder.h"
28 #include "llvm/IR/InstIterator.h"
29 #include "llvm/IR/Instructions.h"
30 #include "llvm/IR/IntrinsicInst.h"
31 #include "llvm/IR/Module.h"
32 #include "llvm/Pass.h"
33 #include "llvm/Support/CommandLine.h"
34 #include "llvm/Support/Debug.h"
35 #include "llvm/Support/FileSystem.h"
36 #include "llvm/Support/Path.h"
37 #include "llvm/Support/raw_ostream.h"
38 #include "llvm/Transforms/Utils/ModuleUtils.h"
39 #include <algorithm>
40 #include <memory>
41 #include <string>
42 #include <utility>
43 using namespace llvm;
44 
45 #define DEBUG_TYPE "insert-gcov-profiling"
46 
47 static cl::opt<std::string>
48 DefaultGCOVVersion("default-gcov-version", cl::init("402*"), cl::Hidden,
49                    cl::ValueRequired);
50 static cl::opt<bool> DefaultExitBlockBeforeBody("gcov-exit-block-before-body",
51                                                 cl::init(false), cl::Hidden);
52 
53 GCOVOptions GCOVOptions::getDefault() {
54   GCOVOptions Options;
55   Options.EmitNotes = true;
56   Options.EmitData = true;
57   Options.UseCfgChecksum = false;
58   Options.NoRedZone = false;
59   Options.FunctionNamesInData = true;
60 
61   if (DefaultGCOVVersion.size() != 4) {
62     llvm::report_fatal_error(std::string("Invalid -default-gcov-version: ") +
63                              DefaultGCOVVersion);
64   }
65   memcpy(Options.Version, DefaultGCOVVersion.c_str(), 4);
66   return Options;
67 }
68 
69 namespace {
70   class GCOVFunction;
71 
72   class GCOVProfiler : public ModulePass {
73   public:
74     static char ID;
75     GCOVProfiler() : ModulePass(ID), Options(GCOVOptions::getDefault()) {
76       init();
77     }
78     GCOVProfiler(const GCOVOptions &Options) : ModulePass(ID), Options(Options){
79       assert((Options.EmitNotes || Options.EmitData) &&
80              "GCOVProfiler asked to do nothing?");
81       init();
82     }
83     const char *getPassName() const override {
84       return "GCOV Profiler";
85     }
86 
87   private:
88     void init() {
89       ReversedVersion[0] = Options.Version[3];
90       ReversedVersion[1] = Options.Version[2];
91       ReversedVersion[2] = Options.Version[1];
92       ReversedVersion[3] = Options.Version[0];
93       ReversedVersion[4] = '\0';
94       initializeGCOVProfilerPass(*PassRegistry::getPassRegistry());
95     }
96     bool runOnModule(Module &M) override;
97 
98     // Create the .gcno files for the Module based on DebugInfo.
99     void emitProfileNotes();
100 
101     // Modify the program to track transitions along edges and call into the
102     // profiling runtime to emit .gcda files when run.
103     bool emitProfileArcs();
104 
105     // Get pointers to the functions in the runtime library.
106     Constant *getStartFileFunc();
107     Constant *getIncrementIndirectCounterFunc();
108     Constant *getEmitFunctionFunc();
109     Constant *getEmitArcsFunc();
110     Constant *getSummaryInfoFunc();
111     Constant *getDeleteWriteoutFunctionListFunc();
112     Constant *getDeleteFlushFunctionListFunc();
113     Constant *getEndFileFunc();
114 
115     // Create or retrieve an i32 state value that is used to represent the
116     // pred block number for certain non-trivial edges.
117     GlobalVariable *getEdgeStateValue();
118 
119     // Produce a table of pointers to counters, by predecessor and successor
120     // block number.
121     GlobalVariable *buildEdgeLookupTable(Function *F,
122                                          GlobalVariable *Counter,
123                                          const UniqueVector<BasicBlock *>&Preds,
124                                          const UniqueVector<BasicBlock*>&Succs);
125 
126     // Add the function to write out all our counters to the global destructor
127     // list.
128     Function *insertCounterWriteout(ArrayRef<std::pair<GlobalVariable*,
129                                                        MDNode*> >);
130     Function *insertFlush(ArrayRef<std::pair<GlobalVariable*, MDNode*> >);
131     void insertIndirectCounterIncrement();
132 
133     std::string mangleName(DICompileUnit CU, const char *NewStem);
134 
135     GCOVOptions Options;
136 
137     // Reversed, NUL-terminated copy of Options.Version.
138     char ReversedVersion[5];
139     // Checksum, produced by hash of EdgeDestinations
140     SmallVector<uint32_t, 4> FileChecksums;
141 
142     Module *M;
143     LLVMContext *Ctx;
144     SmallVector<std::unique_ptr<GCOVFunction>, 16> Funcs;
145   };
146 }
147 
148 char GCOVProfiler::ID = 0;
149 INITIALIZE_PASS(GCOVProfiler, "insert-gcov-profiling",
150                 "Insert instrumentation for GCOV profiling", false, false)
151 
152 ModulePass *llvm::createGCOVProfilerPass(const GCOVOptions &Options) {
153   return new GCOVProfiler(Options);
154 }
155 
156 static StringRef getFunctionName(DISubprogram SP) {
157   if (!SP.getLinkageName().empty())
158     return SP.getLinkageName();
159   return SP.getName();
160 }
161 
162 namespace {
163   class GCOVRecord {
164    protected:
165     static const char *const LinesTag;
166     static const char *const FunctionTag;
167     static const char *const BlockTag;
168     static const char *const EdgeTag;
169 
170     GCOVRecord() {}
171 
172     void writeBytes(const char *Bytes, int Size) {
173       os->write(Bytes, Size);
174     }
175 
176     void write(uint32_t i) {
177       writeBytes(reinterpret_cast<char*>(&i), 4);
178     }
179 
180     // Returns the length measured in 4-byte blocks that will be used to
181     // represent this string in a GCOV file
182     static unsigned lengthOfGCOVString(StringRef s) {
183       // A GCOV string is a length, followed by a NUL, then between 0 and 3 NULs
184       // padding out to the next 4-byte word. The length is measured in 4-byte
185       // words including padding, not bytes of actual string.
186       return (s.size() / 4) + 1;
187     }
188 
189     void writeGCOVString(StringRef s) {
190       uint32_t Len = lengthOfGCOVString(s);
191       write(Len);
192       writeBytes(s.data(), s.size());
193 
194       // Write 1 to 4 bytes of NUL padding.
195       assert((unsigned)(4 - (s.size() % 4)) > 0);
196       assert((unsigned)(4 - (s.size() % 4)) <= 4);
197       writeBytes("\0\0\0\0", 4 - (s.size() % 4));
198     }
199 
200     raw_ostream *os;
201   };
202   const char *const GCOVRecord::LinesTag = "\0\0\x45\x01";
203   const char *const GCOVRecord::FunctionTag = "\0\0\0\1";
204   const char *const GCOVRecord::BlockTag = "\0\0\x41\x01";
205   const char *const GCOVRecord::EdgeTag = "\0\0\x43\x01";
206 
207   class GCOVFunction;
208   class GCOVBlock;
209 
210   // Constructed only by requesting it from a GCOVBlock, this object stores a
211   // list of line numbers and a single filename, representing lines that belong
212   // to the block.
213   class GCOVLines : public GCOVRecord {
214    public:
215     void addLine(uint32_t Line) {
216       assert(Line != 0 && "Line zero is not a valid real line number.");
217       Lines.push_back(Line);
218     }
219 
220     uint32_t length() const {
221       // Here 2 = 1 for string length + 1 for '0' id#.
222       return lengthOfGCOVString(Filename) + 2 + Lines.size();
223     }
224 
225     void writeOut() {
226       write(0);
227       writeGCOVString(Filename);
228       for (int i = 0, e = Lines.size(); i != e; ++i)
229         write(Lines[i]);
230     }
231 
232     GCOVLines(StringRef F, raw_ostream *os)
233       : Filename(F) {
234       this->os = os;
235     }
236 
237    private:
238     StringRef Filename;
239     SmallVector<uint32_t, 32> Lines;
240   };
241 
242 
243   // Represent a basic block in GCOV. Each block has a unique number in the
244   // function, number of lines belonging to each block, and a set of edges to
245   // other blocks.
246   class GCOVBlock : public GCOVRecord {
247    public:
248     GCOVLines &getFile(StringRef Filename) {
249       GCOVLines *&Lines = LinesByFile[Filename];
250       if (!Lines) {
251         Lines = new GCOVLines(Filename, os);
252       }
253       return *Lines;
254     }
255 
256     void addEdge(GCOVBlock &Successor) {
257       OutEdges.push_back(&Successor);
258     }
259 
260     void writeOut() {
261       uint32_t Len = 3;
262       SmallVector<StringMapEntry<GCOVLines *> *, 32> SortedLinesByFile;
263       for (StringMap<GCOVLines *>::iterator I = LinesByFile.begin(),
264                E = LinesByFile.end(); I != E; ++I) {
265         Len += I->second->length();
266         SortedLinesByFile.push_back(&*I);
267       }
268 
269       writeBytes(LinesTag, 4);
270       write(Len);
271       write(Number);
272 
273       std::sort(SortedLinesByFile.begin(), SortedLinesByFile.end(),
274                 [](StringMapEntry<GCOVLines *> *LHS,
275                    StringMapEntry<GCOVLines *> *RHS) {
276         return LHS->getKey() < RHS->getKey();
277       });
278       for (SmallVectorImpl<StringMapEntry<GCOVLines *> *>::iterator
279                I = SortedLinesByFile.begin(), E = SortedLinesByFile.end();
280            I != E; ++I)
281         (*I)->getValue()->writeOut();
282       write(0);
283       write(0);
284     }
285 
286     ~GCOVBlock() {
287       DeleteContainerSeconds(LinesByFile);
288     }
289 
290     GCOVBlock(const GCOVBlock &RHS) : GCOVRecord(RHS), Number(RHS.Number) {
291       // Only allow copy before edges and lines have been added. After that,
292       // there are inter-block pointers (eg: edges) that won't take kindly to
293       // blocks being copied or moved around.
294       assert(LinesByFile.empty());
295       assert(OutEdges.empty());
296     }
297 
298    private:
299     friend class GCOVFunction;
300 
301     GCOVBlock(uint32_t Number, raw_ostream *os)
302         : Number(Number) {
303       this->os = os;
304     }
305 
306     uint32_t Number;
307     StringMap<GCOVLines *> LinesByFile;
308     SmallVector<GCOVBlock *, 4> OutEdges;
309   };
310 
311   // A function has a unique identifier, a checksum (we leave as zero) and a
312   // set of blocks and a map of edges between blocks. This is the only GCOV
313   // object users can construct, the blocks and lines will be rooted here.
314   class GCOVFunction : public GCOVRecord {
315    public:
316      GCOVFunction(DISubprogram SP, raw_ostream *os, uint32_t Ident,
317                   bool UseCfgChecksum, bool ExitBlockBeforeBody)
318          : SP(SP), Ident(Ident), UseCfgChecksum(UseCfgChecksum), CfgChecksum(0),
319            ReturnBlock(1, os) {
320       this->os = os;
321 
322       Function *F = SP.getFunction();
323       DEBUG(dbgs() << "Function: " << getFunctionName(SP) << "\n");
324 
325       uint32_t i = 0;
326       for (auto &BB : *F) {
327         // Skip index 1 if it's assigned to the ReturnBlock.
328         if (i == 1 && ExitBlockBeforeBody)
329           ++i;
330         Blocks.insert(std::make_pair(&BB, GCOVBlock(i++, os)));
331       }
332       if (!ExitBlockBeforeBody)
333         ReturnBlock.Number = i;
334 
335       std::string FunctionNameAndLine;
336       raw_string_ostream FNLOS(FunctionNameAndLine);
337       FNLOS << getFunctionName(SP) << SP.getLineNumber();
338       FNLOS.flush();
339       FuncChecksum = hash_value(FunctionNameAndLine);
340     }
341 
342     GCOVBlock &getBlock(BasicBlock *BB) {
343       return Blocks.find(BB)->second;
344     }
345 
346     GCOVBlock &getReturnBlock() {
347       return ReturnBlock;
348     }
349 
350     std::string getEdgeDestinations() {
351       std::string EdgeDestinations;
352       raw_string_ostream EDOS(EdgeDestinations);
353       Function *F = Blocks.begin()->first->getParent();
354       for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
355         GCOVBlock &Block = getBlock(I);
356         for (int i = 0, e = Block.OutEdges.size(); i != e; ++i)
357           EDOS << Block.OutEdges[i]->Number;
358       }
359       return EdgeDestinations;
360     }
361 
362     uint32_t getFuncChecksum() {
363       return FuncChecksum;
364     }
365 
366     void setCfgChecksum(uint32_t Checksum) {
367       CfgChecksum = Checksum;
368     }
369 
370     void writeOut() {
371       writeBytes(FunctionTag, 4);
372       uint32_t BlockLen = 1 + 1 + 1 + lengthOfGCOVString(getFunctionName(SP)) +
373           1 + lengthOfGCOVString(SP.getFilename()) + 1;
374       if (UseCfgChecksum)
375         ++BlockLen;
376       write(BlockLen);
377       write(Ident);
378       write(FuncChecksum);
379       if (UseCfgChecksum)
380         write(CfgChecksum);
381       writeGCOVString(getFunctionName(SP));
382       writeGCOVString(SP.getFilename());
383       write(SP.getLineNumber());
384 
385       // Emit count of blocks.
386       writeBytes(BlockTag, 4);
387       write(Blocks.size() + 1);
388       for (int i = 0, e = Blocks.size() + 1; i != e; ++i) {
389         write(0);  // No flags on our blocks.
390       }
391       DEBUG(dbgs() << Blocks.size() << " blocks.\n");
392 
393       // Emit edges between blocks.
394       if (Blocks.empty()) return;
395       Function *F = Blocks.begin()->first->getParent();
396       for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
397         GCOVBlock &Block = getBlock(I);
398         if (Block.OutEdges.empty()) continue;
399 
400         writeBytes(EdgeTag, 4);
401         write(Block.OutEdges.size() * 2 + 1);
402         write(Block.Number);
403         for (int i = 0, e = Block.OutEdges.size(); i != e; ++i) {
404           DEBUG(dbgs() << Block.Number << " -> " << Block.OutEdges[i]->Number
405                        << "\n");
406           write(Block.OutEdges[i]->Number);
407           write(0);  // no flags
408         }
409       }
410 
411       // Emit lines for each block.
412       for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
413         getBlock(I).writeOut();
414       }
415     }
416 
417    private:
418     DISubprogram SP;
419     uint32_t Ident;
420     uint32_t FuncChecksum;
421     bool UseCfgChecksum;
422     uint32_t CfgChecksum;
423     DenseMap<BasicBlock *, GCOVBlock> Blocks;
424     GCOVBlock ReturnBlock;
425   };
426 }
427 
428 std::string GCOVProfiler::mangleName(DICompileUnit CU, const char *NewStem) {
429   if (NamedMDNode *GCov = M->getNamedMetadata("llvm.gcov")) {
430     for (int i = 0, e = GCov->getNumOperands(); i != e; ++i) {
431       MDNode *N = GCov->getOperand(i);
432       if (N->getNumOperands() != 2) continue;
433       MDString *GCovFile = dyn_cast<MDString>(N->getOperand(0));
434       MDNode *CompileUnit = dyn_cast<MDNode>(N->getOperand(1));
435       if (!GCovFile || !CompileUnit) continue;
436       if (CompileUnit == CU) {
437         SmallString<128> Filename = GCovFile->getString();
438         sys::path::replace_extension(Filename, NewStem);
439         return Filename.str();
440       }
441     }
442   }
443 
444   SmallString<128> Filename = CU.getFilename();
445   sys::path::replace_extension(Filename, NewStem);
446   StringRef FName = sys::path::filename(Filename);
447   SmallString<128> CurPath;
448   if (sys::fs::current_path(CurPath)) return FName;
449   sys::path::append(CurPath, FName.str());
450   return CurPath.str();
451 }
452 
453 bool GCOVProfiler::runOnModule(Module &M) {
454   this->M = &M;
455   Ctx = &M.getContext();
456 
457   if (Options.EmitNotes) emitProfileNotes();
458   if (Options.EmitData) return emitProfileArcs();
459   return false;
460 }
461 
462 static bool functionHasLines(Function *F) {
463   // Check whether this function actually has any source lines. Not only
464   // do these waste space, they also can crash gcov.
465   for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
466     for (BasicBlock::iterator I = BB->begin(), IE = BB->end();
467          I != IE; ++I) {
468       // Debug intrinsic locations correspond to the location of the
469       // declaration, not necessarily any statements or expressions.
470       if (isa<DbgInfoIntrinsic>(I)) continue;
471 
472       const DebugLoc &Loc = I->getDebugLoc();
473       if (Loc.isUnknown()) continue;
474 
475       // Artificial lines such as calls to the global constructors.
476       if (Loc.getLine() == 0) continue;
477 
478       return true;
479     }
480   }
481   return false;
482 }
483 
484 void GCOVProfiler::emitProfileNotes() {
485   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
486   if (!CU_Nodes) return;
487 
488   for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
489     // Each compile unit gets its own .gcno file. This means that whether we run
490     // this pass over the original .o's as they're produced, or run it after
491     // LTO, we'll generate the same .gcno files.
492 
493     DICompileUnit CU(CU_Nodes->getOperand(i));
494     std::error_code EC;
495     raw_fd_ostream out(mangleName(CU, "gcno"), EC, sys::fs::F_None);
496     std::string EdgeDestinations;
497 
498     DIArray SPs = CU.getSubprograms();
499     unsigned FunctionIdent = 0;
500     for (unsigned i = 0, e = SPs.getNumElements(); i != e; ++i) {
501       DISubprogram SP(SPs.getElement(i));
502       assert((!SP || SP.isSubprogram()) &&
503         "A MDNode in subprograms of a CU should be null or a DISubprogram.");
504       if (!SP)
505         continue;
506 
507       Function *F = SP.getFunction();
508       if (!F) continue;
509       if (!functionHasLines(F)) continue;
510 
511       // gcov expects every function to start with an entry block that has a
512       // single successor, so split the entry block to make sure of that.
513       BasicBlock &EntryBlock = F->getEntryBlock();
514       BasicBlock::iterator It = EntryBlock.begin();
515       while (isa<AllocaInst>(*It) || isa<DbgInfoIntrinsic>(*It))
516         ++It;
517       EntryBlock.splitBasicBlock(It);
518 
519       Funcs.push_back(make_unique<GCOVFunction>(SP, &out, FunctionIdent++,
520                                                 Options.UseCfgChecksum,
521                                                 DefaultExitBlockBeforeBody));
522       GCOVFunction &Func = *Funcs.back();
523 
524       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
525         GCOVBlock &Block = Func.getBlock(BB);
526         TerminatorInst *TI = BB->getTerminator();
527         if (int successors = TI->getNumSuccessors()) {
528           for (int i = 0; i != successors; ++i) {
529             Block.addEdge(Func.getBlock(TI->getSuccessor(i)));
530           }
531         } else if (isa<ReturnInst>(TI)) {
532           Block.addEdge(Func.getReturnBlock());
533         }
534 
535         uint32_t Line = 0;
536         for (BasicBlock::iterator I = BB->begin(), IE = BB->end();
537              I != IE; ++I) {
538           // Debug intrinsic locations correspond to the location of the
539           // declaration, not necessarily any statements or expressions.
540           if (isa<DbgInfoIntrinsic>(I)) continue;
541 
542           const DebugLoc &Loc = I->getDebugLoc();
543           if (Loc.isUnknown()) continue;
544 
545           // Artificial lines such as calls to the global constructors.
546           if (Loc.getLine() == 0) continue;
547 
548           if (Line == Loc.getLine()) continue;
549           Line = Loc.getLine();
550           if (SP != getDISubprogram(Loc.getScope(*Ctx))) continue;
551 
552           GCOVLines &Lines = Block.getFile(SP.getFilename());
553           Lines.addLine(Loc.getLine());
554         }
555       }
556       EdgeDestinations += Func.getEdgeDestinations();
557     }
558 
559     FileChecksums.push_back(hash_value(EdgeDestinations));
560     out.write("oncg", 4);
561     out.write(ReversedVersion, 4);
562     out.write(reinterpret_cast<char*>(&FileChecksums.back()), 4);
563 
564     for (auto &Func : Funcs) {
565       Func->setCfgChecksum(FileChecksums.back());
566       Func->writeOut();
567     }
568 
569     out.write("\0\0\0\0\0\0\0\0", 8);  // EOF
570     out.close();
571   }
572 }
573 
574 bool GCOVProfiler::emitProfileArcs() {
575   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
576   if (!CU_Nodes) return false;
577 
578   bool Result = false;
579   bool InsertIndCounterIncrCode = false;
580   for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
581     DICompileUnit CU(CU_Nodes->getOperand(i));
582     DIArray SPs = CU.getSubprograms();
583     SmallVector<std::pair<GlobalVariable *, MDNode *>, 8> CountersBySP;
584     for (unsigned i = 0, e = SPs.getNumElements(); i != e; ++i) {
585       DISubprogram SP(SPs.getElement(i));
586       assert((!SP || SP.isSubprogram()) &&
587         "A MDNode in subprograms of a CU should be null or a DISubprogram.");
588       if (!SP)
589         continue;
590       Function *F = SP.getFunction();
591       if (!F) continue;
592       if (!functionHasLines(F)) continue;
593       if (!Result) Result = true;
594       unsigned Edges = 0;
595       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
596         TerminatorInst *TI = BB->getTerminator();
597         if (isa<ReturnInst>(TI))
598           ++Edges;
599         else
600           Edges += TI->getNumSuccessors();
601       }
602 
603       ArrayType *CounterTy =
604         ArrayType::get(Type::getInt64Ty(*Ctx), Edges);
605       GlobalVariable *Counters =
606         new GlobalVariable(*M, CounterTy, false,
607                            GlobalValue::InternalLinkage,
608                            Constant::getNullValue(CounterTy),
609                            "__llvm_gcov_ctr");
610       CountersBySP.push_back(std::make_pair(Counters, (MDNode*)SP));
611 
612       UniqueVector<BasicBlock *> ComplexEdgePreds;
613       UniqueVector<BasicBlock *> ComplexEdgeSuccs;
614 
615       unsigned Edge = 0;
616       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
617         TerminatorInst *TI = BB->getTerminator();
618         int Successors = isa<ReturnInst>(TI) ? 1 : TI->getNumSuccessors();
619         if (Successors) {
620           if (Successors == 1) {
621             IRBuilder<> Builder(BB->getFirstInsertionPt());
622             Value *Counter = Builder.CreateConstInBoundsGEP2_64(Counters, 0,
623                                                                 Edge);
624             Value *Count = Builder.CreateLoad(Counter);
625             Count = Builder.CreateAdd(Count, Builder.getInt64(1));
626             Builder.CreateStore(Count, Counter);
627           } else if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
628             IRBuilder<> Builder(BI);
629             Value *Sel = Builder.CreateSelect(BI->getCondition(),
630                                               Builder.getInt64(Edge),
631                                               Builder.getInt64(Edge + 1));
632             SmallVector<Value *, 2> Idx;
633             Idx.push_back(Builder.getInt64(0));
634             Idx.push_back(Sel);
635             Value *Counter = Builder.CreateInBoundsGEP(Counters, Idx);
636             Value *Count = Builder.CreateLoad(Counter);
637             Count = Builder.CreateAdd(Count, Builder.getInt64(1));
638             Builder.CreateStore(Count, Counter);
639           } else {
640             ComplexEdgePreds.insert(BB);
641             for (int i = 0; i != Successors; ++i)
642               ComplexEdgeSuccs.insert(TI->getSuccessor(i));
643           }
644 
645           Edge += Successors;
646         }
647       }
648 
649       if (!ComplexEdgePreds.empty()) {
650         GlobalVariable *EdgeTable =
651           buildEdgeLookupTable(F, Counters,
652                                ComplexEdgePreds, ComplexEdgeSuccs);
653         GlobalVariable *EdgeState = getEdgeStateValue();
654 
655         for (int i = 0, e = ComplexEdgePreds.size(); i != e; ++i) {
656           IRBuilder<> Builder(ComplexEdgePreds[i + 1]->getFirstInsertionPt());
657           Builder.CreateStore(Builder.getInt32(i), EdgeState);
658         }
659 
660         for (int i = 0, e = ComplexEdgeSuccs.size(); i != e; ++i) {
661           // Call runtime to perform increment.
662           IRBuilder<> Builder(ComplexEdgeSuccs[i+1]->getFirstInsertionPt());
663           Value *CounterPtrArray =
664             Builder.CreateConstInBoundsGEP2_64(EdgeTable, 0,
665                                                i * ComplexEdgePreds.size());
666 
667           // Build code to increment the counter.
668           InsertIndCounterIncrCode = true;
669           Builder.CreateCall2(getIncrementIndirectCounterFunc(),
670                               EdgeState, CounterPtrArray);
671         }
672       }
673     }
674 
675     Function *WriteoutF = insertCounterWriteout(CountersBySP);
676     Function *FlushF = insertFlush(CountersBySP);
677 
678     // Create a small bit of code that registers the "__llvm_gcov_writeout" to
679     // be executed at exit and the "__llvm_gcov_flush" function to be executed
680     // when "__gcov_flush" is called.
681     FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
682     Function *F = Function::Create(FTy, GlobalValue::InternalLinkage,
683                                    "__llvm_gcov_init", M);
684     F->setUnnamedAddr(true);
685     F->setLinkage(GlobalValue::InternalLinkage);
686     F->addFnAttr(Attribute::NoInline);
687     if (Options.NoRedZone)
688       F->addFnAttr(Attribute::NoRedZone);
689 
690     BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", F);
691     IRBuilder<> Builder(BB);
692 
693     FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
694     Type *Params[] = {
695       PointerType::get(FTy, 0),
696       PointerType::get(FTy, 0)
697     };
698     FTy = FunctionType::get(Builder.getVoidTy(), Params, false);
699 
700     // Initialize the environment and register the local writeout and flush
701     // functions.
702     Constant *GCOVInit = M->getOrInsertFunction("llvm_gcov_init", FTy);
703     Builder.CreateCall2(GCOVInit, WriteoutF, FlushF);
704     Builder.CreateRetVoid();
705 
706     appendToGlobalCtors(*M, F, 0);
707   }
708 
709   if (InsertIndCounterIncrCode)
710     insertIndirectCounterIncrement();
711 
712   return Result;
713 }
714 
715 // All edges with successors that aren't branches are "complex", because it
716 // requires complex logic to pick which counter to update.
717 GlobalVariable *GCOVProfiler::buildEdgeLookupTable(
718     Function *F,
719     GlobalVariable *Counters,
720     const UniqueVector<BasicBlock *> &Preds,
721     const UniqueVector<BasicBlock *> &Succs) {
722   // TODO: support invoke, threads. We rely on the fact that nothing can modify
723   // the whole-Module pred edge# between the time we set it and the time we next
724   // read it. Threads and invoke make this untrue.
725 
726   // emit [(succs * preds) x i64*], logically [succ x [pred x i64*]].
727   size_t TableSize = Succs.size() * Preds.size();
728   Type *Int64PtrTy = Type::getInt64PtrTy(*Ctx);
729   ArrayType *EdgeTableTy = ArrayType::get(Int64PtrTy, TableSize);
730 
731   std::unique_ptr<Constant * []> EdgeTable(new Constant *[TableSize]);
732   Constant *NullValue = Constant::getNullValue(Int64PtrTy);
733   for (size_t i = 0; i != TableSize; ++i)
734     EdgeTable[i] = NullValue;
735 
736   unsigned Edge = 0;
737   for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
738     TerminatorInst *TI = BB->getTerminator();
739     int Successors = isa<ReturnInst>(TI) ? 1 : TI->getNumSuccessors();
740     if (Successors > 1 && !isa<BranchInst>(TI) && !isa<ReturnInst>(TI)) {
741       for (int i = 0; i != Successors; ++i) {
742         BasicBlock *Succ = TI->getSuccessor(i);
743         IRBuilder<> Builder(Succ);
744         Value *Counter = Builder.CreateConstInBoundsGEP2_64(Counters, 0,
745                                                             Edge + i);
746         EdgeTable[((Succs.idFor(Succ)-1) * Preds.size()) +
747                   (Preds.idFor(BB)-1)] = cast<Constant>(Counter);
748       }
749     }
750     Edge += Successors;
751   }
752 
753   GlobalVariable *EdgeTableGV =
754       new GlobalVariable(
755           *M, EdgeTableTy, true, GlobalValue::InternalLinkage,
756           ConstantArray::get(EdgeTableTy,
757                              makeArrayRef(&EdgeTable[0],TableSize)),
758           "__llvm_gcda_edge_table");
759   EdgeTableGV->setUnnamedAddr(true);
760   return EdgeTableGV;
761 }
762 
763 Constant *GCOVProfiler::getStartFileFunc() {
764   Type *Args[] = {
765     Type::getInt8PtrTy(*Ctx),  // const char *orig_filename
766     Type::getInt8PtrTy(*Ctx),  // const char version[4]
767     Type::getInt32Ty(*Ctx),    // uint32_t checksum
768   };
769   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
770   return M->getOrInsertFunction("llvm_gcda_start_file", FTy);
771 }
772 
773 Constant *GCOVProfiler::getIncrementIndirectCounterFunc() {
774   Type *Int32Ty = Type::getInt32Ty(*Ctx);
775   Type *Int64Ty = Type::getInt64Ty(*Ctx);
776   Type *Args[] = {
777     Int32Ty->getPointerTo(),                // uint32_t *predecessor
778     Int64Ty->getPointerTo()->getPointerTo() // uint64_t **counters
779   };
780   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
781   return M->getOrInsertFunction("__llvm_gcov_indirect_counter_increment", FTy);
782 }
783 
784 Constant *GCOVProfiler::getEmitFunctionFunc() {
785   Type *Args[] = {
786     Type::getInt32Ty(*Ctx),    // uint32_t ident
787     Type::getInt8PtrTy(*Ctx),  // const char *function_name
788     Type::getInt32Ty(*Ctx),    // uint32_t func_checksum
789     Type::getInt8Ty(*Ctx),     // uint8_t use_extra_checksum
790     Type::getInt32Ty(*Ctx),    // uint32_t cfg_checksum
791   };
792   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
793   return M->getOrInsertFunction("llvm_gcda_emit_function", FTy);
794 }
795 
796 Constant *GCOVProfiler::getEmitArcsFunc() {
797   Type *Args[] = {
798     Type::getInt32Ty(*Ctx),     // uint32_t num_counters
799     Type::getInt64PtrTy(*Ctx),  // uint64_t *counters
800   };
801   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
802   return M->getOrInsertFunction("llvm_gcda_emit_arcs", FTy);
803 }
804 
805 Constant *GCOVProfiler::getSummaryInfoFunc() {
806   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
807   return M->getOrInsertFunction("llvm_gcda_summary_info", FTy);
808 }
809 
810 Constant *GCOVProfiler::getDeleteWriteoutFunctionListFunc() {
811   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
812   return M->getOrInsertFunction("llvm_delete_writeout_function_list", FTy);
813 }
814 
815 Constant *GCOVProfiler::getDeleteFlushFunctionListFunc() {
816   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
817   return M->getOrInsertFunction("llvm_delete_flush_function_list", FTy);
818 }
819 
820 Constant *GCOVProfiler::getEndFileFunc() {
821   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
822   return M->getOrInsertFunction("llvm_gcda_end_file", FTy);
823 }
824 
825 GlobalVariable *GCOVProfiler::getEdgeStateValue() {
826   GlobalVariable *GV = M->getGlobalVariable("__llvm_gcov_global_state_pred");
827   if (!GV) {
828     GV = new GlobalVariable(*M, Type::getInt32Ty(*Ctx), false,
829                             GlobalValue::InternalLinkage,
830                             ConstantInt::get(Type::getInt32Ty(*Ctx),
831                                              0xffffffff),
832                             "__llvm_gcov_global_state_pred");
833     GV->setUnnamedAddr(true);
834   }
835   return GV;
836 }
837 
838 Function *GCOVProfiler::insertCounterWriteout(
839     ArrayRef<std::pair<GlobalVariable *, MDNode *> > CountersBySP) {
840   FunctionType *WriteoutFTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
841   Function *WriteoutF = M->getFunction("__llvm_gcov_writeout");
842   if (!WriteoutF)
843     WriteoutF = Function::Create(WriteoutFTy, GlobalValue::InternalLinkage,
844                                  "__llvm_gcov_writeout", M);
845   WriteoutF->setUnnamedAddr(true);
846   WriteoutF->addFnAttr(Attribute::NoInline);
847   if (Options.NoRedZone)
848     WriteoutF->addFnAttr(Attribute::NoRedZone);
849 
850   BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", WriteoutF);
851   IRBuilder<> Builder(BB);
852 
853   Constant *StartFile = getStartFileFunc();
854   Constant *EmitFunction = getEmitFunctionFunc();
855   Constant *EmitArcs = getEmitArcsFunc();
856   Constant *SummaryInfo = getSummaryInfoFunc();
857   Constant *EndFile = getEndFileFunc();
858 
859   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
860   if (CU_Nodes) {
861     for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
862       DICompileUnit CU(CU_Nodes->getOperand(i));
863       std::string FilenameGcda = mangleName(CU, "gcda");
864       uint32_t CfgChecksum = FileChecksums.empty() ? 0 : FileChecksums[i];
865       Builder.CreateCall3(StartFile,
866                           Builder.CreateGlobalStringPtr(FilenameGcda),
867                           Builder.CreateGlobalStringPtr(ReversedVersion),
868                           Builder.getInt32(CfgChecksum));
869       for (unsigned j = 0, e = CountersBySP.size(); j != e; ++j) {
870         DISubprogram SP(CountersBySP[j].second);
871         uint32_t FuncChecksum = Funcs.empty() ? 0 : Funcs[j]->getFuncChecksum();
872         Builder.CreateCall5(
873             EmitFunction, Builder.getInt32(j),
874             Options.FunctionNamesInData ?
875               Builder.CreateGlobalStringPtr(getFunctionName(SP)) :
876               Constant::getNullValue(Builder.getInt8PtrTy()),
877             Builder.getInt32(FuncChecksum),
878             Builder.getInt8(Options.UseCfgChecksum),
879             Builder.getInt32(CfgChecksum));
880 
881         GlobalVariable *GV = CountersBySP[j].first;
882         unsigned Arcs =
883           cast<ArrayType>(GV->getType()->getElementType())->getNumElements();
884         Builder.CreateCall2(EmitArcs,
885                             Builder.getInt32(Arcs),
886                             Builder.CreateConstGEP2_64(GV, 0, 0));
887       }
888       Builder.CreateCall(SummaryInfo);
889       Builder.CreateCall(EndFile);
890     }
891   }
892 
893   Builder.CreateRetVoid();
894   return WriteoutF;
895 }
896 
897 void GCOVProfiler::insertIndirectCounterIncrement() {
898   Function *Fn =
899     cast<Function>(GCOVProfiler::getIncrementIndirectCounterFunc());
900   Fn->setUnnamedAddr(true);
901   Fn->setLinkage(GlobalValue::InternalLinkage);
902   Fn->addFnAttr(Attribute::NoInline);
903   if (Options.NoRedZone)
904     Fn->addFnAttr(Attribute::NoRedZone);
905 
906   // Create basic blocks for function.
907   BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", Fn);
908   IRBuilder<> Builder(BB);
909 
910   BasicBlock *PredNotNegOne = BasicBlock::Create(*Ctx, "", Fn);
911   BasicBlock *CounterEnd = BasicBlock::Create(*Ctx, "", Fn);
912   BasicBlock *Exit = BasicBlock::Create(*Ctx, "exit", Fn);
913 
914   // uint32_t pred = *predecessor;
915   // if (pred == 0xffffffff) return;
916   Argument *Arg = Fn->arg_begin();
917   Arg->setName("predecessor");
918   Value *Pred = Builder.CreateLoad(Arg, "pred");
919   Value *Cond = Builder.CreateICmpEQ(Pred, Builder.getInt32(0xffffffff));
920   BranchInst::Create(Exit, PredNotNegOne, Cond, BB);
921 
922   Builder.SetInsertPoint(PredNotNegOne);
923 
924   // uint64_t *counter = counters[pred];
925   // if (!counter) return;
926   Value *ZExtPred = Builder.CreateZExt(Pred, Builder.getInt64Ty());
927   Arg = std::next(Fn->arg_begin());
928   Arg->setName("counters");
929   Value *GEP = Builder.CreateGEP(Arg, ZExtPred);
930   Value *Counter = Builder.CreateLoad(GEP, "counter");
931   Cond = Builder.CreateICmpEQ(Counter,
932                               Constant::getNullValue(
933                                   Builder.getInt64Ty()->getPointerTo()));
934   Builder.CreateCondBr(Cond, Exit, CounterEnd);
935 
936   // ++*counter;
937   Builder.SetInsertPoint(CounterEnd);
938   Value *Add = Builder.CreateAdd(Builder.CreateLoad(Counter),
939                                  Builder.getInt64(1));
940   Builder.CreateStore(Add, Counter);
941   Builder.CreateBr(Exit);
942 
943   // Fill in the exit block.
944   Builder.SetInsertPoint(Exit);
945   Builder.CreateRetVoid();
946 }
947 
948 Function *GCOVProfiler::
949 insertFlush(ArrayRef<std::pair<GlobalVariable*, MDNode*> > CountersBySP) {
950   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
951   Function *FlushF = M->getFunction("__llvm_gcov_flush");
952   if (!FlushF)
953     FlushF = Function::Create(FTy, GlobalValue::InternalLinkage,
954                               "__llvm_gcov_flush", M);
955   else
956     FlushF->setLinkage(GlobalValue::InternalLinkage);
957   FlushF->setUnnamedAddr(true);
958   FlushF->addFnAttr(Attribute::NoInline);
959   if (Options.NoRedZone)
960     FlushF->addFnAttr(Attribute::NoRedZone);
961 
962   BasicBlock *Entry = BasicBlock::Create(*Ctx, "entry", FlushF);
963 
964   // Write out the current counters.
965   Constant *WriteoutF = M->getFunction("__llvm_gcov_writeout");
966   assert(WriteoutF && "Need to create the writeout function first!");
967 
968   IRBuilder<> Builder(Entry);
969   Builder.CreateCall(WriteoutF);
970 
971   // Zero out the counters.
972   for (ArrayRef<std::pair<GlobalVariable *, MDNode *> >::iterator
973          I = CountersBySP.begin(), E = CountersBySP.end();
974        I != E; ++I) {
975     GlobalVariable *GV = I->first;
976     Constant *Null = Constant::getNullValue(GV->getType()->getElementType());
977     Builder.CreateStore(Null, GV);
978   }
979 
980   Type *RetTy = FlushF->getReturnType();
981   if (RetTy == Type::getVoidTy(*Ctx))
982     Builder.CreateRetVoid();
983   else if (RetTy->isIntegerTy())
984     // Used if __llvm_gcov_flush was implicitly declared.
985     Builder.CreateRet(ConstantInt::get(RetTy, 0));
986   else
987     report_fatal_error("invalid return type for __llvm_gcov_flush");
988 
989   return FlushF;
990 }
991