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