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