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