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/InstIterator.h"
36 #include "llvm/Support/PathV2.h"
37 #include "llvm/Support/raw_ostream.h"
38 #include "llvm/Transforms/Utils/ModuleUtils.h"
39 #include <string>
40 #include <utility>
41 using namespace llvm;
42 
43 static cl::opt<std::string>
44 DefaultGCOVVersion("default-gcov-version", cl::init("402*"), cl::Hidden,
45                    cl::ValueRequired);
46 
47 GCOVOptions GCOVOptions::getDefault() {
48   GCOVOptions Options;
49   Options.EmitNotes = true;
50   Options.EmitData = true;
51   Options.UseCfgChecksum = false;
52   Options.NoRedZone = false;
53   Options.FunctionNamesInData = true;
54 
55   if (DefaultGCOVVersion.size() != 4) {
56     llvm::report_fatal_error(std::string("Invalid -default-gcov-version: ") +
57                              DefaultGCOVVersion);
58   }
59   memcpy(Options.Version, DefaultGCOVVersion.c_str(), 4);
60   return Options;
61 }
62 
63 namespace {
64   class GCOVProfiler : public ModulePass {
65   public:
66     static char ID;
67     GCOVProfiler() : ModulePass(ID), Options(GCOVOptions::getDefault()) {
68       ReversedVersion[0] = Options.Version[3];
69       ReversedVersion[1] = Options.Version[2];
70       ReversedVersion[2] = Options.Version[1];
71       ReversedVersion[3] = Options.Version[0];
72       ReversedVersion[4] = '\0';
73       initializeGCOVProfilerPass(*PassRegistry::getPassRegistry());
74     }
75     GCOVProfiler(const GCOVOptions &Options) : ModulePass(ID), Options(Options){
76       assert((Options.EmitNotes || Options.EmitData) &&
77              "GCOVProfiler asked to do nothing?");
78       ReversedVersion[0] = Options.Version[3];
79       ReversedVersion[1] = Options.Version[2];
80       ReversedVersion[2] = Options.Version[1];
81       ReversedVersion[3] = Options.Version[0];
82       ReversedVersion[4] = '\0';
83       initializeGCOVProfilerPass(*PassRegistry::getPassRegistry());
84     }
85     virtual const char *getPassName() const {
86       return "GCOV Profiler";
87     }
88 
89   private:
90     bool runOnModule(Module &M);
91 
92     // Create the .gcno files for the Module based on DebugInfo.
93     void emitProfileNotes();
94 
95     // Modify the program to track transitions along edges and call into the
96     // profiling runtime to emit .gcda files when run.
97     bool emitProfileArcs();
98 
99     // Get pointers to the functions in the runtime library.
100     Constant *getStartFileFunc();
101     Constant *getIncrementIndirectCounterFunc();
102     Constant *getEmitFunctionFunc();
103     Constant *getEmitArcsFunc();
104     Constant *getDeleteWriteoutFunctionListFunc();
105     Constant *getDeleteFlushFunctionListFunc();
106     Constant *getEndFileFunc();
107 
108     // Create or retrieve an i32 state value that is used to represent the
109     // pred block number for certain non-trivial edges.
110     GlobalVariable *getEdgeStateValue();
111 
112     // Produce a table of pointers to counters, by predecessor and successor
113     // block number.
114     GlobalVariable *buildEdgeLookupTable(Function *F,
115                                          GlobalVariable *Counter,
116                                          const UniqueVector<BasicBlock *>&Preds,
117                                          const UniqueVector<BasicBlock*>&Succs);
118 
119     // Add the function to write out all our counters to the global destructor
120     // list.
121     Function *insertCounterWriteout(ArrayRef<std::pair<GlobalVariable*,
122                                                        MDNode*> >);
123     Function *insertFlush(ArrayRef<std::pair<GlobalVariable*, MDNode*> >);
124     void insertIndirectCounterIncrement();
125 
126     std::string mangleName(DICompileUnit CU, const char *NewStem);
127 
128     GCOVOptions Options;
129 
130     // Reversed, NUL-terminated copy of Options.Version.
131     char ReversedVersion[5];
132 
133     Module *M;
134     LLVMContext *Ctx;
135   };
136 }
137 
138 char GCOVProfiler::ID = 0;
139 INITIALIZE_PASS(GCOVProfiler, "insert-gcov-profiling",
140                 "Insert instrumentation for GCOV profiling", false, false)
141 
142 ModulePass *llvm::createGCOVProfilerPass(const GCOVOptions &Options) {
143   return new GCOVProfiler(Options);
144 }
145 
146 static std::string getFunctionName(DISubprogram SP) {
147   if (!SP.getLinkageName().empty())
148     return SP.getLinkageName();
149   return SP.getName();
150 }
151 
152 namespace {
153   class GCOVRecord {
154    protected:
155     static const char *LinesTag;
156     static const char *FunctionTag;
157     static const char *BlockTag;
158     static const char *EdgeTag;
159 
160     GCOVRecord() {}
161 
162     void writeBytes(const char *Bytes, int Size) {
163       os->write(Bytes, Size);
164     }
165 
166     void write(uint32_t i) {
167       writeBytes(reinterpret_cast<char*>(&i), 4);
168     }
169 
170     // Returns the length measured in 4-byte blocks that will be used to
171     // represent this string in a GCOV file
172     unsigned lengthOfGCOVString(StringRef s) {
173       // A GCOV string is a length, followed by a NUL, then between 0 and 3 NULs
174       // padding out to the next 4-byte word. The length is measured in 4-byte
175       // words including padding, not bytes of actual string.
176       return (s.size() / 4) + 1;
177     }
178 
179     void writeGCOVString(StringRef s) {
180       uint32_t Len = lengthOfGCOVString(s);
181       write(Len);
182       writeBytes(s.data(), s.size());
183 
184       // Write 1 to 4 bytes of NUL padding.
185       assert((unsigned)(4 - (s.size() % 4)) > 0);
186       assert((unsigned)(4 - (s.size() % 4)) <= 4);
187       writeBytes("\0\0\0\0", 4 - (s.size() % 4));
188     }
189 
190     raw_ostream *os;
191   };
192   const char *GCOVRecord::LinesTag = "\0\0\x45\x01";
193   const char *GCOVRecord::FunctionTag = "\0\0\0\1";
194   const char *GCOVRecord::BlockTag = "\0\0\x41\x01";
195   const char *GCOVRecord::EdgeTag = "\0\0\x43\x01";
196 
197   class GCOVFunction;
198   class GCOVBlock;
199 
200   // Constructed only by requesting it from a GCOVBlock, this object stores a
201   // list of line numbers and a single filename, representing lines that belong
202   // to the block.
203   class GCOVLines : public GCOVRecord {
204    public:
205     void addLine(uint32_t Line) {
206       Lines.push_back(Line);
207     }
208 
209     uint32_t length() {
210       // Here 2 = 1 for string length + 1 for '0' id#.
211       return lengthOfGCOVString(Filename) + 2 + Lines.size();
212     }
213 
214     void writeOut() {
215       write(0);
216       writeGCOVString(Filename);
217       for (int i = 0, e = Lines.size(); i != e; ++i)
218         write(Lines[i]);
219     }
220 
221     GCOVLines(StringRef F, raw_ostream *os)
222       : Filename(F) {
223       this->os = os;
224     }
225 
226    private:
227     StringRef Filename;
228     SmallVector<uint32_t, 32> Lines;
229   };
230 
231   // Represent a basic block in GCOV. Each block has a unique number in the
232   // function, number of lines belonging to each block, and a set of edges to
233   // other blocks.
234   class GCOVBlock : public GCOVRecord {
235    public:
236     GCOVLines &getFile(StringRef Filename) {
237       GCOVLines *&Lines = LinesByFile[Filename];
238       if (!Lines) {
239         Lines = new GCOVLines(Filename, os);
240       }
241       return *Lines;
242     }
243 
244     void addEdge(GCOVBlock &Successor) {
245       OutEdges.push_back(&Successor);
246     }
247 
248     void writeOut() {
249       uint32_t Len = 3;
250       for (StringMap<GCOVLines *>::iterator I = LinesByFile.begin(),
251                E = LinesByFile.end(); I != E; ++I) {
252         Len += I->second->length();
253       }
254 
255       writeBytes(LinesTag, 4);
256       write(Len);
257       write(Number);
258       for (StringMap<GCOVLines *>::iterator I = LinesByFile.begin(),
259                E = LinesByFile.end(); I != E; ++I)
260         I->second->writeOut();
261       write(0);
262       write(0);
263     }
264 
265     ~GCOVBlock() {
266       DeleteContainerSeconds(LinesByFile);
267     }
268 
269    private:
270     friend class GCOVFunction;
271 
272     GCOVBlock(uint32_t Number, raw_ostream *os)
273         : Number(Number) {
274       this->os = os;
275     }
276 
277     uint32_t Number;
278     StringMap<GCOVLines *> LinesByFile;
279     SmallVector<GCOVBlock *, 4> OutEdges;
280   };
281 
282   // A function has a unique identifier, a checksum (we leave as zero) and a
283   // set of blocks and a map of edges between blocks. This is the only GCOV
284   // object users can construct, the blocks and lines will be rooted here.
285   class GCOVFunction : public GCOVRecord {
286    public:
287     GCOVFunction(DISubprogram SP, raw_ostream *os, uint32_t Ident,
288                  bool UseCfgChecksum) {
289       this->os = os;
290 
291       Function *F = SP.getFunction();
292       DEBUG(dbgs() << "Function: " << F->getName() << "\n");
293       uint32_t i = 0;
294       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
295         Blocks[BB] = new GCOVBlock(i++, os);
296       }
297       ReturnBlock = new GCOVBlock(i++, os);
298 
299       writeBytes(FunctionTag, 4);
300       uint32_t BlockLen = 1 + 1 + 1 + lengthOfGCOVString(getFunctionName(SP)) +
301           1 + lengthOfGCOVString(SP.getFilename()) + 1;
302       if (UseCfgChecksum)
303         ++BlockLen;
304       write(BlockLen);
305       write(Ident);
306       write(0);  // lineno checksum
307       if (UseCfgChecksum)
308         write(0);  // cfg checksum
309       writeGCOVString(getFunctionName(SP));
310       writeGCOVString(SP.getFilename());
311       write(SP.getLineNumber());
312     }
313 
314     ~GCOVFunction() {
315       DeleteContainerSeconds(Blocks);
316       delete ReturnBlock;
317     }
318 
319     GCOVBlock &getBlock(BasicBlock *BB) {
320       return *Blocks[BB];
321     }
322 
323     GCOVBlock &getReturnBlock() {
324       return *ReturnBlock;
325     }
326 
327     void writeOut() {
328       // Emit count of blocks.
329       writeBytes(BlockTag, 4);
330       write(Blocks.size() + 1);
331       for (int i = 0, e = Blocks.size() + 1; i != e; ++i) {
332         write(0);  // No flags on our blocks.
333       }
334       DEBUG(dbgs() << Blocks.size() << " blocks.\n");
335 
336       // Emit edges between blocks.
337       for (DenseMap<BasicBlock *, GCOVBlock *>::iterator I = Blocks.begin(),
338                E = Blocks.end(); I != E; ++I) {
339         GCOVBlock &Block = *I->second;
340         if (Block.OutEdges.empty()) continue;
341 
342         writeBytes(EdgeTag, 4);
343         write(Block.OutEdges.size() * 2 + 1);
344         write(Block.Number);
345         for (int i = 0, e = Block.OutEdges.size(); i != e; ++i) {
346           DEBUG(dbgs() << Block.Number << " -> " << Block.OutEdges[i]->Number
347                        << "\n");
348           write(Block.OutEdges[i]->Number);
349           write(0);  // no flags
350         }
351       }
352 
353       // Emit lines for each block.
354       for (DenseMap<BasicBlock *, GCOVBlock *>::iterator I = Blocks.begin(),
355                E = Blocks.end(); I != E; ++I) {
356         I->second->writeOut();
357       }
358     }
359 
360    private:
361     DenseMap<BasicBlock *, GCOVBlock *> Blocks;
362     GCOVBlock *ReturnBlock;
363   };
364 }
365 
366 std::string GCOVProfiler::mangleName(DICompileUnit CU, const char *NewStem) {
367   if (NamedMDNode *GCov = M->getNamedMetadata("llvm.gcov")) {
368     for (int i = 0, e = GCov->getNumOperands(); i != e; ++i) {
369       MDNode *N = GCov->getOperand(i);
370       if (N->getNumOperands() != 2) continue;
371       MDString *GCovFile = dyn_cast<MDString>(N->getOperand(0));
372       MDNode *CompileUnit = dyn_cast<MDNode>(N->getOperand(1));
373       if (!GCovFile || !CompileUnit) continue;
374       if (CompileUnit == CU) {
375         SmallString<128> Filename = GCovFile->getString();
376         sys::path::replace_extension(Filename, NewStem);
377         return Filename.str();
378       }
379     }
380   }
381 
382   SmallString<128> Filename = CU.getFilename();
383   sys::path::replace_extension(Filename, NewStem);
384   return sys::path::filename(Filename.str());
385 }
386 
387 bool GCOVProfiler::runOnModule(Module &M) {
388   this->M = &M;
389   Ctx = &M.getContext();
390 
391   if (Options.EmitNotes) emitProfileNotes();
392   if (Options.EmitData) return emitProfileArcs();
393   return false;
394 }
395 
396 void GCOVProfiler::emitProfileNotes() {
397   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
398   if (!CU_Nodes) return;
399 
400   for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
401     // Each compile unit gets its own .gcno file. This means that whether we run
402     // this pass over the original .o's as they're produced, or run it after
403     // LTO, we'll generate the same .gcno files.
404 
405     DICompileUnit CU(CU_Nodes->getOperand(i));
406     std::string ErrorInfo;
407     raw_fd_ostream out(mangleName(CU, "gcno").c_str(), ErrorInfo,
408                        raw_fd_ostream::F_Binary);
409     out.write("oncg", 4);
410     out.write(ReversedVersion, 4);
411     out.write("MVLL", 4);
412 
413     DIArray SPs = CU.getSubprograms();
414     for (unsigned i = 0, e = SPs.getNumElements(); i != e; ++i) {
415       DISubprogram SP(SPs.getElement(i));
416       if (!SP.Verify()) continue;
417 
418       Function *F = SP.getFunction();
419       if (!F) continue;
420       GCOVFunction Func(SP, &out, i, Options.UseCfgChecksum);
421 
422       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
423         GCOVBlock &Block = Func.getBlock(BB);
424         TerminatorInst *TI = BB->getTerminator();
425         if (int successors = TI->getNumSuccessors()) {
426           for (int i = 0; i != successors; ++i) {
427             Block.addEdge(Func.getBlock(TI->getSuccessor(i)));
428           }
429         } else if (isa<ReturnInst>(TI)) {
430           Block.addEdge(Func.getReturnBlock());
431         }
432 
433         uint32_t Line = 0;
434         for (BasicBlock::iterator I = BB->begin(), IE = BB->end();
435              I != IE; ++I) {
436           const DebugLoc &Loc = I->getDebugLoc();
437           if (Loc.isUnknown()) continue;
438           if (Line == Loc.getLine()) continue;
439           Line = Loc.getLine();
440           if (SP != getDISubprogram(Loc.getScope(*Ctx))) continue;
441 
442           GCOVLines &Lines = Block.getFile(SP.getFilename());
443           Lines.addLine(Loc.getLine());
444         }
445       }
446       Func.writeOut();
447     }
448     out.write("\0\0\0\0\0\0\0\0", 8);  // EOF
449     out.close();
450   }
451 }
452 
453 bool GCOVProfiler::emitProfileArcs() {
454   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
455   if (!CU_Nodes) return false;
456 
457   bool Result = false;
458   bool InsertIndCounterIncrCode = false;
459   for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
460     DICompileUnit CU(CU_Nodes->getOperand(i));
461     DIArray SPs = CU.getSubprograms();
462     SmallVector<std::pair<GlobalVariable *, MDNode *>, 8> CountersBySP;
463     for (unsigned i = 0, e = SPs.getNumElements(); i != e; ++i) {
464       DISubprogram SP(SPs.getElement(i));
465       if (!SP.Verify()) continue;
466       Function *F = SP.getFunction();
467       if (!F) continue;
468       if (!Result) Result = true;
469       unsigned Edges = 0;
470       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
471         TerminatorInst *TI = BB->getTerminator();
472         if (isa<ReturnInst>(TI))
473           ++Edges;
474         else
475           Edges += TI->getNumSuccessors();
476       }
477 
478       ArrayType *CounterTy =
479         ArrayType::get(Type::getInt64Ty(*Ctx), Edges);
480       GlobalVariable *Counters =
481         new GlobalVariable(*M, CounterTy, false,
482                            GlobalValue::InternalLinkage,
483                            Constant::getNullValue(CounterTy),
484                            "__llvm_gcov_ctr");
485       CountersBySP.push_back(std::make_pair(Counters, (MDNode*)SP));
486 
487       UniqueVector<BasicBlock *> ComplexEdgePreds;
488       UniqueVector<BasicBlock *> ComplexEdgeSuccs;
489 
490       unsigned Edge = 0;
491       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
492         TerminatorInst *TI = BB->getTerminator();
493         int Successors = isa<ReturnInst>(TI) ? 1 : TI->getNumSuccessors();
494         if (Successors) {
495           IRBuilder<> Builder(TI);
496 
497           if (Successors == 1) {
498             Value *Counter = Builder.CreateConstInBoundsGEP2_64(Counters, 0,
499                                                                 Edge);
500             Value *Count = Builder.CreateLoad(Counter);
501             Count = Builder.CreateAdd(Count, Builder.getInt64(1));
502             Builder.CreateStore(Count, Counter);
503           } else if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
504             Value *Sel = Builder.CreateSelect(BI->getCondition(),
505                                               Builder.getInt64(Edge),
506                                               Builder.getInt64(Edge + 1));
507             SmallVector<Value *, 2> Idx;
508             Idx.push_back(Builder.getInt64(0));
509             Idx.push_back(Sel);
510             Value *Counter = Builder.CreateInBoundsGEP(Counters, Idx);
511             Value *Count = Builder.CreateLoad(Counter);
512             Count = Builder.CreateAdd(Count, Builder.getInt64(1));
513             Builder.CreateStore(Count, Counter);
514           } else {
515             ComplexEdgePreds.insert(BB);
516             for (int i = 0; i != Successors; ++i)
517               ComplexEdgeSuccs.insert(TI->getSuccessor(i));
518           }
519           Edge += Successors;
520         }
521       }
522 
523       if (!ComplexEdgePreds.empty()) {
524         GlobalVariable *EdgeTable =
525           buildEdgeLookupTable(F, Counters,
526                                ComplexEdgePreds, ComplexEdgeSuccs);
527         GlobalVariable *EdgeState = getEdgeStateValue();
528 
529         for (int i = 0, e = ComplexEdgePreds.size(); i != e; ++i) {
530           IRBuilder<> Builder(ComplexEdgePreds[i+1]->getTerminator());
531           Builder.CreateStore(Builder.getInt32(i), EdgeState);
532         }
533         for (int i = 0, e = ComplexEdgeSuccs.size(); i != e; ++i) {
534           // call runtime to perform increment
535           BasicBlock::iterator InsertPt =
536             ComplexEdgeSuccs[i+1]->getFirstInsertionPt();
537           IRBuilder<> Builder(InsertPt);
538           Value *CounterPtrArray =
539             Builder.CreateConstInBoundsGEP2_64(EdgeTable, 0,
540                                                i * ComplexEdgePreds.size());
541 
542           // Build code to increment the counter.
543           InsertIndCounterIncrCode = true;
544           Builder.CreateCall2(getIncrementIndirectCounterFunc(),
545                               EdgeState, CounterPtrArray);
546         }
547       }
548     }
549 
550     Function *WriteoutF = insertCounterWriteout(CountersBySP);
551     Function *FlushF = insertFlush(CountersBySP);
552 
553     // Create a small bit of code that registers the "__llvm_gcov_writeout" to
554     // be executed at exit and the "__llvm_gcov_flush" function to be executed
555     // when "__gcov_flush" is called.
556     FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
557     Function *F = Function::Create(FTy, GlobalValue::InternalLinkage,
558                                    "__llvm_gcov_init", M);
559     F->setUnnamedAddr(true);
560     F->setLinkage(GlobalValue::InternalLinkage);
561     F->addFnAttr(Attribute::NoInline);
562     if (Options.NoRedZone)
563       F->addFnAttr(Attribute::NoRedZone);
564 
565     BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", F);
566     IRBuilder<> Builder(BB);
567 
568     FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
569     Type *Params[] = {
570       PointerType::get(FTy, 0),
571       PointerType::get(FTy, 0)
572     };
573     FTy = FunctionType::get(Builder.getVoidTy(), Params, false);
574 
575     // Inialize the environment and register the local writeout and flush
576     // functions.
577     Constant *GCOVInit = M->getOrInsertFunction("llvm_gcov_init", FTy);
578     Builder.CreateCall2(GCOVInit, WriteoutF, FlushF);
579     Builder.CreateRetVoid();
580 
581     appendToGlobalCtors(*M, F, 0);
582   }
583 
584   if (InsertIndCounterIncrCode)
585     insertIndirectCounterIncrement();
586 
587   return Result;
588 }
589 
590 // All edges with successors that aren't branches are "complex", because it
591 // requires complex logic to pick which counter to update.
592 GlobalVariable *GCOVProfiler::buildEdgeLookupTable(
593     Function *F,
594     GlobalVariable *Counters,
595     const UniqueVector<BasicBlock *> &Preds,
596     const UniqueVector<BasicBlock *> &Succs) {
597   // TODO: support invoke, threads. We rely on the fact that nothing can modify
598   // the whole-Module pred edge# between the time we set it and the time we next
599   // read it. Threads and invoke make this untrue.
600 
601   // emit [(succs * preds) x i64*], logically [succ x [pred x i64*]].
602   size_t TableSize = Succs.size() * Preds.size();
603   Type *Int64PtrTy = Type::getInt64PtrTy(*Ctx);
604   ArrayType *EdgeTableTy = ArrayType::get(Int64PtrTy, TableSize);
605 
606   OwningArrayPtr<Constant *> EdgeTable(new Constant*[TableSize]);
607   Constant *NullValue = Constant::getNullValue(Int64PtrTy);
608   for (size_t i = 0; i != TableSize; ++i)
609     EdgeTable[i] = NullValue;
610 
611   unsigned Edge = 0;
612   for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
613     TerminatorInst *TI = BB->getTerminator();
614     int Successors = isa<ReturnInst>(TI) ? 1 : TI->getNumSuccessors();
615     if (Successors > 1 && !isa<BranchInst>(TI) && !isa<ReturnInst>(TI)) {
616       for (int i = 0; i != Successors; ++i) {
617         BasicBlock *Succ = TI->getSuccessor(i);
618         IRBuilder<> Builder(Succ);
619         Value *Counter = Builder.CreateConstInBoundsGEP2_64(Counters, 0,
620                                                             Edge + i);
621         EdgeTable[((Succs.idFor(Succ)-1) * Preds.size()) +
622                   (Preds.idFor(BB)-1)] = cast<Constant>(Counter);
623       }
624     }
625     Edge += Successors;
626   }
627 
628   ArrayRef<Constant*> V(&EdgeTable[0], TableSize);
629   GlobalVariable *EdgeTableGV =
630       new GlobalVariable(
631           *M, EdgeTableTy, true, GlobalValue::InternalLinkage,
632           ConstantArray::get(EdgeTableTy, V),
633           "__llvm_gcda_edge_table");
634   EdgeTableGV->setUnnamedAddr(true);
635   return EdgeTableGV;
636 }
637 
638 Constant *GCOVProfiler::getStartFileFunc() {
639   Type *Args[] = {
640     Type::getInt8PtrTy(*Ctx),  // const char *orig_filename
641     Type::getInt8PtrTy(*Ctx),  // const char version[4]
642   };
643   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
644   return M->getOrInsertFunction("llvm_gcda_start_file", FTy);
645 }
646 
647 Constant *GCOVProfiler::getIncrementIndirectCounterFunc() {
648   Type *Int32Ty = Type::getInt32Ty(*Ctx);
649   Type *Int64Ty = Type::getInt64Ty(*Ctx);
650   Type *Args[] = {
651     Int32Ty->getPointerTo(),                // uint32_t *predecessor
652     Int64Ty->getPointerTo()->getPointerTo() // uint64_t **counters
653   };
654   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
655   return M->getOrInsertFunction("__llvm_gcov_indirect_counter_increment", FTy);
656 }
657 
658 Constant *GCOVProfiler::getEmitFunctionFunc() {
659   Type *Args[3] = {
660     Type::getInt32Ty(*Ctx),    // uint32_t ident
661     Type::getInt8PtrTy(*Ctx),  // const char *function_name
662     Type::getInt8Ty(*Ctx),     // uint8_t use_extra_checksum
663   };
664   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
665   return M->getOrInsertFunction("llvm_gcda_emit_function", FTy);
666 }
667 
668 Constant *GCOVProfiler::getEmitArcsFunc() {
669   Type *Args[] = {
670     Type::getInt32Ty(*Ctx),     // uint32_t num_counters
671     Type::getInt64PtrTy(*Ctx),  // uint64_t *counters
672   };
673   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
674   return M->getOrInsertFunction("llvm_gcda_emit_arcs", FTy);
675 }
676 
677 Constant *GCOVProfiler::getDeleteWriteoutFunctionListFunc() {
678   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
679   return M->getOrInsertFunction("llvm_delete_writeout_function_list", FTy);
680 }
681 
682 Constant *GCOVProfiler::getDeleteFlushFunctionListFunc() {
683   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
684   return M->getOrInsertFunction("llvm_delete_flush_function_list", FTy);
685 }
686 
687 Constant *GCOVProfiler::getEndFileFunc() {
688   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
689   return M->getOrInsertFunction("llvm_gcda_end_file", FTy);
690 }
691 
692 GlobalVariable *GCOVProfiler::getEdgeStateValue() {
693   GlobalVariable *GV = M->getGlobalVariable("__llvm_gcov_global_state_pred");
694   if (!GV) {
695     GV = new GlobalVariable(*M, Type::getInt32Ty(*Ctx), false,
696                             GlobalValue::InternalLinkage,
697                             ConstantInt::get(Type::getInt32Ty(*Ctx),
698                                              0xffffffff),
699                             "__llvm_gcov_global_state_pred");
700     GV->setUnnamedAddr(true);
701   }
702   return GV;
703 }
704 
705 Function *GCOVProfiler::insertCounterWriteout(
706     ArrayRef<std::pair<GlobalVariable *, MDNode *> > CountersBySP) {
707   FunctionType *WriteoutFTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
708   Function *WriteoutF = M->getFunction("__llvm_gcov_writeout");
709   if (!WriteoutF)
710     WriteoutF = Function::Create(WriteoutFTy, GlobalValue::InternalLinkage,
711                                  "__llvm_gcov_writeout", M);
712   WriteoutF->setUnnamedAddr(true);
713   WriteoutF->addFnAttr(Attribute::NoInline);
714   if (Options.NoRedZone)
715     WriteoutF->addFnAttr(Attribute::NoRedZone);
716 
717   BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", WriteoutF);
718   IRBuilder<> Builder(BB);
719 
720   Constant *StartFile = getStartFileFunc();
721   Constant *EmitFunction = getEmitFunctionFunc();
722   Constant *EmitArcs = getEmitArcsFunc();
723   Constant *EndFile = getEndFileFunc();
724 
725   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
726   if (CU_Nodes) {
727     for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
728       DICompileUnit CU(CU_Nodes->getOperand(i));
729       std::string FilenameGcda = mangleName(CU, "gcda");
730       Builder.CreateCall2(StartFile,
731                           Builder.CreateGlobalStringPtr(FilenameGcda),
732                           Builder.CreateGlobalStringPtr(ReversedVersion));
733       for (unsigned j = 0, e = CountersBySP.size(); j != e; ++j) {
734         DISubprogram SP(CountersBySP[j].second);
735         Builder.CreateCall3(
736             EmitFunction, Builder.getInt32(j),
737             Options.FunctionNamesInData ?
738               Builder.CreateGlobalStringPtr(getFunctionName(SP)) :
739               Constant::getNullValue(Builder.getInt8PtrTy()),
740             Builder.getInt8(Options.UseCfgChecksum));
741 
742         GlobalVariable *GV = CountersBySP[j].first;
743         unsigned Arcs =
744           cast<ArrayType>(GV->getType()->getElementType())->getNumElements();
745         Builder.CreateCall2(EmitArcs,
746                             Builder.getInt32(Arcs),
747                             Builder.CreateConstGEP2_64(GV, 0, 0));
748       }
749       Builder.CreateCall(EndFile);
750     }
751   }
752 
753   Builder.CreateRetVoid();
754   return WriteoutF;
755 }
756 
757 void GCOVProfiler::insertIndirectCounterIncrement() {
758   Function *Fn =
759     cast<Function>(GCOVProfiler::getIncrementIndirectCounterFunc());
760   Fn->setUnnamedAddr(true);
761   Fn->setLinkage(GlobalValue::InternalLinkage);
762   Fn->addFnAttr(Attribute::NoInline);
763   if (Options.NoRedZone)
764     Fn->addFnAttr(Attribute::NoRedZone);
765 
766   // Create basic blocks for function.
767   BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", Fn);
768   IRBuilder<> Builder(BB);
769 
770   BasicBlock *PredNotNegOne = BasicBlock::Create(*Ctx, "", Fn);
771   BasicBlock *CounterEnd = BasicBlock::Create(*Ctx, "", Fn);
772   BasicBlock *Exit = BasicBlock::Create(*Ctx, "exit", Fn);
773 
774   // uint32_t pred = *predecessor;
775   // if (pred == 0xffffffff) return;
776   Argument *Arg = Fn->arg_begin();
777   Arg->setName("predecessor");
778   Value *Pred = Builder.CreateLoad(Arg, "pred");
779   Value *Cond = Builder.CreateICmpEQ(Pred, Builder.getInt32(0xffffffff));
780   BranchInst::Create(Exit, PredNotNegOne, Cond, BB);
781 
782   Builder.SetInsertPoint(PredNotNegOne);
783 
784   // uint64_t *counter = counters[pred];
785   // if (!counter) return;
786   Value *ZExtPred = Builder.CreateZExt(Pred, Builder.getInt64Ty());
787   Arg = llvm::next(Fn->arg_begin());
788   Arg->setName("counters");
789   Value *GEP = Builder.CreateGEP(Arg, ZExtPred);
790   Value *Counter = Builder.CreateLoad(GEP, "counter");
791   Cond = Builder.CreateICmpEQ(Counter,
792                               Constant::getNullValue(
793                                   Builder.getInt64Ty()->getPointerTo()));
794   Builder.CreateCondBr(Cond, Exit, CounterEnd);
795 
796   // ++*counter;
797   Builder.SetInsertPoint(CounterEnd);
798   Value *Add = Builder.CreateAdd(Builder.CreateLoad(Counter),
799                                  Builder.getInt64(1));
800   Builder.CreateStore(Add, Counter);
801   Builder.CreateBr(Exit);
802 
803   // Fill in the exit block.
804   Builder.SetInsertPoint(Exit);
805   Builder.CreateRetVoid();
806 }
807 
808 Function *GCOVProfiler::
809 insertFlush(ArrayRef<std::pair<GlobalVariable*, MDNode*> > CountersBySP) {
810   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
811   Function *FlushF = M->getFunction("__llvm_gcov_flush");
812   if (!FlushF)
813     FlushF = Function::Create(FTy, GlobalValue::InternalLinkage,
814                               "__llvm_gcov_flush", M);
815   else
816     FlushF->setLinkage(GlobalValue::InternalLinkage);
817   FlushF->setUnnamedAddr(true);
818   FlushF->addFnAttr(Attribute::NoInline);
819   if (Options.NoRedZone)
820     FlushF->addFnAttr(Attribute::NoRedZone);
821 
822   BasicBlock *Entry = BasicBlock::Create(*Ctx, "entry", FlushF);
823 
824   // Write out the current counters.
825   Constant *WriteoutF = M->getFunction("__llvm_gcov_writeout");
826   assert(WriteoutF && "Need to create the writeout function first!");
827 
828   IRBuilder<> Builder(Entry);
829   Builder.CreateCall(WriteoutF);
830 
831   // Zero out the counters.
832   for (ArrayRef<std::pair<GlobalVariable *, MDNode *> >::iterator
833          I = CountersBySP.begin(), E = CountersBySP.end();
834        I != E; ++I) {
835     GlobalVariable *GV = I->first;
836     Constant *Null = Constant::getNullValue(GV->getType()->getElementType());
837     Builder.CreateStore(Null, GV);
838   }
839 
840   Type *RetTy = FlushF->getReturnType();
841   if (RetTy == Type::getVoidTy(*Ctx))
842     Builder.CreateRetVoid();
843   else if (RetTy->isIntegerTy())
844     // Used if __llvm_gcov_flush was implicitly declared.
845     Builder.CreateRet(ConstantInt::get(RetTy, 0));
846   else
847     report_fatal_error("invalid return type for __llvm_gcov_flush");
848 
849   return FlushF;
850 }
851