1 //===- GCOVProfiling.cpp - Insert edge counters for gcov profiling --------===//
2 //
3 //                      The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This pass implements GCOV-style profiling. When this pass is run it emits
11 // "gcno" files next to the existing source, and instruments the code that runs
12 // to records the edges between blocks that run and emit a complementary "gcda"
13 // file on exit.
14 //
15 //===----------------------------------------------------------------------===//
16 
17 #include "llvm/Transforms/Instrumentation.h"
18 #include "llvm/ADT/DenseMap.h"
19 #include "llvm/ADT/Hashing.h"
20 #include "llvm/ADT/STLExtras.h"
21 #include "llvm/ADT/Statistic.h"
22 #include "llvm/ADT/StringExtras.h"
23 #include "llvm/ADT/StringMap.h"
24 #include "llvm/ADT/UniqueVector.h"
25 #include "llvm/IR/DebugInfo.h"
26 #include "llvm/IR/DebugLoc.h"
27 #include "llvm/IR/IRBuilder.h"
28 #include "llvm/IR/InstIterator.h"
29 #include "llvm/IR/Instructions.h"
30 #include "llvm/IR/IntrinsicInst.h"
31 #include "llvm/IR/Module.h"
32 #include "llvm/Pass.h"
33 #include "llvm/Support/CommandLine.h"
34 #include "llvm/Support/Debug.h"
35 #include "llvm/Support/FileSystem.h"
36 #include "llvm/Support/Path.h"
37 #include "llvm/Support/raw_ostream.h"
38 #include "llvm/Transforms/Utils/ModuleUtils.h"
39 #include <algorithm>
40 #include <memory>
41 #include <string>
42 #include <utility>
43 using namespace llvm;
44 
45 #define DEBUG_TYPE "insert-gcov-profiling"
46 
47 static cl::opt<std::string>
48 DefaultGCOVVersion("default-gcov-version", cl::init("402*"), cl::Hidden,
49                    cl::ValueRequired);
50 static cl::opt<bool> DefaultExitBlockBeforeBody("gcov-exit-block-before-body",
51                                                 cl::init(false), cl::Hidden);
52 
getDefault()53 GCOVOptions GCOVOptions::getDefault() {
54   GCOVOptions Options;
55   Options.EmitNotes = true;
56   Options.EmitData = true;
57   Options.UseCfgChecksum = false;
58   Options.NoRedZone = false;
59   Options.FunctionNamesInData = true;
60   Options.ExitBlockBeforeBody = DefaultExitBlockBeforeBody;
61 
62   if (DefaultGCOVVersion.size() != 4) {
63     llvm::report_fatal_error(std::string("Invalid -default-gcov-version: ") +
64                              DefaultGCOVVersion);
65   }
66   memcpy(Options.Version, DefaultGCOVVersion.c_str(), 4);
67   return Options;
68 }
69 
70 namespace {
71   class GCOVFunction;
72 
73   class GCOVProfiler : public ModulePass {
74   public:
75     static char ID;
GCOVProfiler()76     GCOVProfiler() : GCOVProfiler(GCOVOptions::getDefault()) {}
GCOVProfiler(const GCOVOptions & Opts)77     GCOVProfiler(const GCOVOptions &Opts) : ModulePass(ID), Options(Opts) {
78       assert((Options.EmitNotes || Options.EmitData) &&
79              "GCOVProfiler asked to do nothing?");
80       ReversedVersion[0] = Options.Version[3];
81       ReversedVersion[1] = Options.Version[2];
82       ReversedVersion[2] = Options.Version[1];
83       ReversedVersion[3] = Options.Version[0];
84       ReversedVersion[4] = '\0';
85       initializeGCOVProfilerPass(*PassRegistry::getPassRegistry());
86     }
getPassName() const87     const char *getPassName() const override {
88       return "GCOV Profiler";
89     }
90 
91   private:
92     bool runOnModule(Module &M) override;
93 
94     // Create the .gcno files for the Module based on DebugInfo.
95     void emitProfileNotes();
96 
97     // Modify the program to track transitions along edges and call into the
98     // profiling runtime to emit .gcda files when run.
99     bool emitProfileArcs();
100 
101     // Get pointers to the functions in the runtime library.
102     Constant *getStartFileFunc();
103     Constant *getIncrementIndirectCounterFunc();
104     Constant *getEmitFunctionFunc();
105     Constant *getEmitArcsFunc();
106     Constant *getSummaryInfoFunc();
107     Constant *getDeleteWriteoutFunctionListFunc();
108     Constant *getDeleteFlushFunctionListFunc();
109     Constant *getEndFileFunc();
110 
111     // Create or retrieve an i32 state value that is used to represent the
112     // pred block number for certain non-trivial edges.
113     GlobalVariable *getEdgeStateValue();
114 
115     // Produce a table of pointers to counters, by predecessor and successor
116     // block number.
117     GlobalVariable *buildEdgeLookupTable(Function *F,
118                                          GlobalVariable *Counter,
119                                          const UniqueVector<BasicBlock *>&Preds,
120                                          const UniqueVector<BasicBlock*>&Succs);
121 
122     // Add the function to write out all our counters to the global destructor
123     // list.
124     Function *insertCounterWriteout(ArrayRef<std::pair<GlobalVariable*,
125                                                        MDNode*> >);
126     Function *insertFlush(ArrayRef<std::pair<GlobalVariable*, MDNode*> >);
127     void insertIndirectCounterIncrement();
128 
129     std::string mangleName(DICompileUnit CU, const char *NewStem);
130 
131     GCOVOptions Options;
132 
133     // Reversed, NUL-terminated copy of Options.Version.
134     char ReversedVersion[5];
135     // Checksum, produced by hash of EdgeDestinations
136     SmallVector<uint32_t, 4> FileChecksums;
137 
138     Module *M;
139     LLVMContext *Ctx;
140     SmallVector<std::unique_ptr<GCOVFunction>, 16> Funcs;
141   };
142 }
143 
144 char GCOVProfiler::ID = 0;
145 INITIALIZE_PASS(GCOVProfiler, "insert-gcov-profiling",
146                 "Insert instrumentation for GCOV profiling", false, false)
147 
createGCOVProfilerPass(const GCOVOptions & Options)148 ModulePass *llvm::createGCOVProfilerPass(const GCOVOptions &Options) {
149   return new GCOVProfiler(Options);
150 }
151 
getFunctionName(MDSubprogram * SP)152 static StringRef getFunctionName(MDSubprogram *SP) {
153   if (!SP->getLinkageName().empty())
154     return SP->getLinkageName();
155   return SP->getName();
156 }
157 
158 namespace {
159   class GCOVRecord {
160    protected:
161     static const char *const LinesTag;
162     static const char *const FunctionTag;
163     static const char *const BlockTag;
164     static const char *const EdgeTag;
165 
166     GCOVRecord() = default;
167 
writeBytes(const char * Bytes,int Size)168     void writeBytes(const char *Bytes, int Size) {
169       os->write(Bytes, Size);
170     }
171 
write(uint32_t i)172     void write(uint32_t i) {
173       writeBytes(reinterpret_cast<char*>(&i), 4);
174     }
175 
176     // Returns the length measured in 4-byte blocks that will be used to
177     // represent this string in a GCOV file
lengthOfGCOVString(StringRef s)178     static unsigned lengthOfGCOVString(StringRef s) {
179       // A GCOV string is a length, followed by a NUL, then between 0 and 3 NULs
180       // padding out to the next 4-byte word. The length is measured in 4-byte
181       // words including padding, not bytes of actual string.
182       return (s.size() / 4) + 1;
183     }
184 
writeGCOVString(StringRef s)185     void writeGCOVString(StringRef s) {
186       uint32_t Len = lengthOfGCOVString(s);
187       write(Len);
188       writeBytes(s.data(), s.size());
189 
190       // Write 1 to 4 bytes of NUL padding.
191       assert((unsigned)(4 - (s.size() % 4)) > 0);
192       assert((unsigned)(4 - (s.size() % 4)) <= 4);
193       writeBytes("\0\0\0\0", 4 - (s.size() % 4));
194     }
195 
196     raw_ostream *os;
197   };
198   const char *const GCOVRecord::LinesTag = "\0\0\x45\x01";
199   const char *const GCOVRecord::FunctionTag = "\0\0\0\1";
200   const char *const GCOVRecord::BlockTag = "\0\0\x41\x01";
201   const char *const GCOVRecord::EdgeTag = "\0\0\x43\x01";
202 
203   class GCOVFunction;
204   class GCOVBlock;
205 
206   // Constructed only by requesting it from a GCOVBlock, this object stores a
207   // list of line numbers and a single filename, representing lines that belong
208   // to the block.
209   class GCOVLines : public GCOVRecord {
210    public:
addLine(uint32_t Line)211     void addLine(uint32_t Line) {
212       assert(Line != 0 && "Line zero is not a valid real line number.");
213       Lines.push_back(Line);
214     }
215 
length() const216     uint32_t length() const {
217       // Here 2 = 1 for string length + 1 for '0' id#.
218       return lengthOfGCOVString(Filename) + 2 + Lines.size();
219     }
220 
writeOut()221     void writeOut() {
222       write(0);
223       writeGCOVString(Filename);
224       for (int i = 0, e = Lines.size(); i != e; ++i)
225         write(Lines[i]);
226     }
227 
GCOVLines(StringRef F,raw_ostream * os)228     GCOVLines(StringRef F, raw_ostream *os)
229       : Filename(F) {
230       this->os = os;
231     }
232 
233    private:
234     StringRef Filename;
235     SmallVector<uint32_t, 32> Lines;
236   };
237 
238 
239   // Represent a basic block in GCOV. Each block has a unique number in the
240   // function, number of lines belonging to each block, and a set of edges to
241   // other blocks.
242   class GCOVBlock : public GCOVRecord {
243    public:
getFile(StringRef Filename)244     GCOVLines &getFile(StringRef Filename) {
245       GCOVLines *&Lines = LinesByFile[Filename];
246       if (!Lines) {
247         Lines = new GCOVLines(Filename, os);
248       }
249       return *Lines;
250     }
251 
addEdge(GCOVBlock & Successor)252     void addEdge(GCOVBlock &Successor) {
253       OutEdges.push_back(&Successor);
254     }
255 
writeOut()256     void writeOut() {
257       uint32_t Len = 3;
258       SmallVector<StringMapEntry<GCOVLines *> *, 32> SortedLinesByFile;
259       for (StringMap<GCOVLines *>::iterator I = LinesByFile.begin(),
260                E = LinesByFile.end(); I != E; ++I) {
261         Len += I->second->length();
262         SortedLinesByFile.push_back(&*I);
263       }
264 
265       writeBytes(LinesTag, 4);
266       write(Len);
267       write(Number);
268 
269       std::sort(SortedLinesByFile.begin(), SortedLinesByFile.end(),
270                 [](StringMapEntry<GCOVLines *> *LHS,
271                    StringMapEntry<GCOVLines *> *RHS) {
272         return LHS->getKey() < RHS->getKey();
273       });
274       for (SmallVectorImpl<StringMapEntry<GCOVLines *> *>::iterator
275                I = SortedLinesByFile.begin(), E = SortedLinesByFile.end();
276            I != E; ++I)
277         (*I)->getValue()->writeOut();
278       write(0);
279       write(0);
280     }
281 
~GCOVBlock()282     ~GCOVBlock() {
283       DeleteContainerSeconds(LinesByFile);
284     }
285 
GCOVBlock(const GCOVBlock & RHS)286     GCOVBlock(const GCOVBlock &RHS) : GCOVRecord(RHS), Number(RHS.Number) {
287       // Only allow copy before edges and lines have been added. After that,
288       // there are inter-block pointers (eg: edges) that won't take kindly to
289       // blocks being copied or moved around.
290       assert(LinesByFile.empty());
291       assert(OutEdges.empty());
292     }
293 
294    private:
295     friend class GCOVFunction;
296 
GCOVBlock(uint32_t Number,raw_ostream * os)297     GCOVBlock(uint32_t Number, raw_ostream *os)
298         : Number(Number) {
299       this->os = os;
300     }
301 
302     uint32_t Number;
303     StringMap<GCOVLines *> LinesByFile;
304     SmallVector<GCOVBlock *, 4> OutEdges;
305   };
306 
307   // A function has a unique identifier, a checksum (we leave as zero) and a
308   // set of blocks and a map of edges between blocks. This is the only GCOV
309   // object users can construct, the blocks and lines will be rooted here.
310   class GCOVFunction : public GCOVRecord {
311    public:
GCOVFunction(DISubprogram SP,raw_ostream * os,uint32_t Ident,bool UseCfgChecksum,bool ExitBlockBeforeBody)312      GCOVFunction(DISubprogram SP, raw_ostream *os, uint32_t Ident,
313                   bool UseCfgChecksum, bool ExitBlockBeforeBody)
314          : SP(SP), Ident(Ident), UseCfgChecksum(UseCfgChecksum), CfgChecksum(0),
315            ReturnBlock(1, os) {
316       this->os = os;
317 
318       Function *F = SP->getFunction();
319       DEBUG(dbgs() << "Function: " << getFunctionName(SP) << "\n");
320 
321       uint32_t i = 0;
322       for (auto &BB : *F) {
323         // Skip index 1 if it's assigned to the ReturnBlock.
324         if (i == 1 && ExitBlockBeforeBody)
325           ++i;
326         Blocks.insert(std::make_pair(&BB, GCOVBlock(i++, os)));
327       }
328       if (!ExitBlockBeforeBody)
329         ReturnBlock.Number = i;
330 
331       std::string FunctionNameAndLine;
332       raw_string_ostream FNLOS(FunctionNameAndLine);
333       FNLOS << getFunctionName(SP) << SP->getLine();
334       FNLOS.flush();
335       FuncChecksum = hash_value(FunctionNameAndLine);
336     }
337 
getBlock(BasicBlock * BB)338     GCOVBlock &getBlock(BasicBlock *BB) {
339       return Blocks.find(BB)->second;
340     }
341 
getReturnBlock()342     GCOVBlock &getReturnBlock() {
343       return ReturnBlock;
344     }
345 
getEdgeDestinations()346     std::string getEdgeDestinations() {
347       std::string EdgeDestinations;
348       raw_string_ostream EDOS(EdgeDestinations);
349       Function *F = Blocks.begin()->first->getParent();
350       for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
351         GCOVBlock &Block = getBlock(I);
352         for (int i = 0, e = Block.OutEdges.size(); i != e; ++i)
353           EDOS << Block.OutEdges[i]->Number;
354       }
355       return EdgeDestinations;
356     }
357 
getFuncChecksum()358     uint32_t getFuncChecksum() {
359       return FuncChecksum;
360     }
361 
setCfgChecksum(uint32_t Checksum)362     void setCfgChecksum(uint32_t Checksum) {
363       CfgChecksum = Checksum;
364     }
365 
writeOut()366     void writeOut() {
367       writeBytes(FunctionTag, 4);
368       uint32_t BlockLen = 1 + 1 + 1 + lengthOfGCOVString(getFunctionName(SP)) +
369                           1 + lengthOfGCOVString(SP->getFilename()) + 1;
370       if (UseCfgChecksum)
371         ++BlockLen;
372       write(BlockLen);
373       write(Ident);
374       write(FuncChecksum);
375       if (UseCfgChecksum)
376         write(CfgChecksum);
377       writeGCOVString(getFunctionName(SP));
378       writeGCOVString(SP->getFilename());
379       write(SP->getLine());
380 
381       // Emit count of blocks.
382       writeBytes(BlockTag, 4);
383       write(Blocks.size() + 1);
384       for (int i = 0, e = Blocks.size() + 1; i != e; ++i) {
385         write(0);  // No flags on our blocks.
386       }
387       DEBUG(dbgs() << Blocks.size() << " blocks.\n");
388 
389       // Emit edges between blocks.
390       if (Blocks.empty()) return;
391       Function *F = Blocks.begin()->first->getParent();
392       for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
393         GCOVBlock &Block = getBlock(I);
394         if (Block.OutEdges.empty()) continue;
395 
396         writeBytes(EdgeTag, 4);
397         write(Block.OutEdges.size() * 2 + 1);
398         write(Block.Number);
399         for (int i = 0, e = Block.OutEdges.size(); i != e; ++i) {
400           DEBUG(dbgs() << Block.Number << " -> " << Block.OutEdges[i]->Number
401                        << "\n");
402           write(Block.OutEdges[i]->Number);
403           write(0);  // no flags
404         }
405       }
406 
407       // Emit lines for each block.
408       for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
409         getBlock(I).writeOut();
410       }
411     }
412 
413    private:
414     DISubprogram SP;
415     uint32_t Ident;
416     uint32_t FuncChecksum;
417     bool UseCfgChecksum;
418     uint32_t CfgChecksum;
419     DenseMap<BasicBlock *, GCOVBlock> Blocks;
420     GCOVBlock ReturnBlock;
421   };
422 }
423 
mangleName(DICompileUnit CU,const char * NewStem)424 std::string GCOVProfiler::mangleName(DICompileUnit CU, const char *NewStem) {
425   if (NamedMDNode *GCov = M->getNamedMetadata("llvm.gcov")) {
426     for (int i = 0, e = GCov->getNumOperands(); i != e; ++i) {
427       MDNode *N = GCov->getOperand(i);
428       if (N->getNumOperands() != 2) continue;
429       MDString *GCovFile = dyn_cast<MDString>(N->getOperand(0));
430       MDNode *CompileUnit = dyn_cast<MDNode>(N->getOperand(1));
431       if (!GCovFile || !CompileUnit) continue;
432       if (CompileUnit == CU) {
433         SmallString<128> Filename = GCovFile->getString();
434         sys::path::replace_extension(Filename, NewStem);
435         return Filename.str();
436       }
437     }
438   }
439 
440   SmallString<128> Filename = CU->getFilename();
441   sys::path::replace_extension(Filename, NewStem);
442   StringRef FName = sys::path::filename(Filename);
443   SmallString<128> CurPath;
444   if (sys::fs::current_path(CurPath)) return FName;
445   sys::path::append(CurPath, FName);
446   return CurPath.str();
447 }
448 
runOnModule(Module & M)449 bool GCOVProfiler::runOnModule(Module &M) {
450   this->M = &M;
451   Ctx = &M.getContext();
452 
453   if (Options.EmitNotes) emitProfileNotes();
454   if (Options.EmitData) return emitProfileArcs();
455   return false;
456 }
457 
functionHasLines(Function * F)458 static bool functionHasLines(Function *F) {
459   // Check whether this function actually has any source lines. Not only
460   // do these waste space, they also can crash gcov.
461   for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
462     for (BasicBlock::iterator I = BB->begin(), IE = BB->end();
463          I != IE; ++I) {
464       // Debug intrinsic locations correspond to the location of the
465       // declaration, not necessarily any statements or expressions.
466       if (isa<DbgInfoIntrinsic>(I)) continue;
467 
468       const DebugLoc &Loc = I->getDebugLoc();
469       if (!Loc)
470         continue;
471 
472       // Artificial lines such as calls to the global constructors.
473       if (Loc.getLine() == 0) continue;
474 
475       return true;
476     }
477   }
478   return false;
479 }
480 
emitProfileNotes()481 void GCOVProfiler::emitProfileNotes() {
482   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
483   if (!CU_Nodes) return;
484 
485   for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
486     // Each compile unit gets its own .gcno file. This means that whether we run
487     // this pass over the original .o's as they're produced, or run it after
488     // LTO, we'll generate the same .gcno files.
489 
490     DICompileUnit CU = cast<MDCompileUnit>(CU_Nodes->getOperand(i));
491     std::error_code EC;
492     raw_fd_ostream out(mangleName(CU, "gcno"), EC, sys::fs::F_None);
493     std::string EdgeDestinations;
494 
495     unsigned FunctionIdent = 0;
496     for (auto *SP : CU->getSubprograms()) {
497       Function *F = SP->getFunction();
498       if (!F) continue;
499       if (!functionHasLines(F)) continue;
500 
501       // gcov expects every function to start with an entry block that has a
502       // single successor, so split the entry block to make sure of that.
503       BasicBlock &EntryBlock = F->getEntryBlock();
504       BasicBlock::iterator It = EntryBlock.begin();
505       while (isa<AllocaInst>(*It) || isa<DbgInfoIntrinsic>(*It))
506         ++It;
507       EntryBlock.splitBasicBlock(It);
508 
509       Funcs.push_back(make_unique<GCOVFunction>(SP, &out, FunctionIdent++,
510                                                 Options.UseCfgChecksum,
511                                                 Options.ExitBlockBeforeBody));
512       GCOVFunction &Func = *Funcs.back();
513 
514       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
515         GCOVBlock &Block = Func.getBlock(BB);
516         TerminatorInst *TI = BB->getTerminator();
517         if (int successors = TI->getNumSuccessors()) {
518           for (int i = 0; i != successors; ++i) {
519             Block.addEdge(Func.getBlock(TI->getSuccessor(i)));
520           }
521         } else if (isa<ReturnInst>(TI)) {
522           Block.addEdge(Func.getReturnBlock());
523         }
524 
525         uint32_t Line = 0;
526         for (BasicBlock::iterator I = BB->begin(), IE = BB->end();
527              I != IE; ++I) {
528           // Debug intrinsic locations correspond to the location of the
529           // declaration, not necessarily any statements or expressions.
530           if (isa<DbgInfoIntrinsic>(I)) continue;
531 
532           const DebugLoc &Loc = I->getDebugLoc();
533           if (!Loc)
534             continue;
535 
536           // Artificial lines such as calls to the global constructors.
537           if (Loc.getLine() == 0) continue;
538 
539           if (Line == Loc.getLine()) continue;
540           Line = Loc.getLine();
541           if (SP != getDISubprogram(Loc.getScope()))
542             continue;
543 
544           GCOVLines &Lines = Block.getFile(SP->getFilename());
545           Lines.addLine(Loc.getLine());
546         }
547       }
548       EdgeDestinations += Func.getEdgeDestinations();
549     }
550 
551     FileChecksums.push_back(hash_value(EdgeDestinations));
552     out.write("oncg", 4);
553     out.write(ReversedVersion, 4);
554     out.write(reinterpret_cast<char*>(&FileChecksums.back()), 4);
555 
556     for (auto &Func : Funcs) {
557       Func->setCfgChecksum(FileChecksums.back());
558       Func->writeOut();
559     }
560 
561     out.write("\0\0\0\0\0\0\0\0", 8);  // EOF
562     out.close();
563   }
564 }
565 
emitProfileArcs()566 bool GCOVProfiler::emitProfileArcs() {
567   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
568   if (!CU_Nodes) return false;
569 
570   bool Result = false;
571   bool InsertIndCounterIncrCode = false;
572   for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
573     DICompileUnit CU = cast<MDCompileUnit>(CU_Nodes->getOperand(i));
574     SmallVector<std::pair<GlobalVariable *, MDNode *>, 8> CountersBySP;
575     for (auto *SP : CU->getSubprograms()) {
576       Function *F = SP->getFunction();
577       if (!F) continue;
578       if (!functionHasLines(F)) continue;
579       if (!Result) Result = true;
580       unsigned Edges = 0;
581       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
582         TerminatorInst *TI = BB->getTerminator();
583         if (isa<ReturnInst>(TI))
584           ++Edges;
585         else
586           Edges += TI->getNumSuccessors();
587       }
588 
589       ArrayType *CounterTy =
590         ArrayType::get(Type::getInt64Ty(*Ctx), Edges);
591       GlobalVariable *Counters =
592         new GlobalVariable(*M, CounterTy, false,
593                            GlobalValue::InternalLinkage,
594                            Constant::getNullValue(CounterTy),
595                            "__llvm_gcov_ctr");
596       CountersBySP.push_back(std::make_pair(Counters, SP));
597 
598       UniqueVector<BasicBlock *> ComplexEdgePreds;
599       UniqueVector<BasicBlock *> ComplexEdgeSuccs;
600 
601       unsigned Edge = 0;
602       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
603         TerminatorInst *TI = BB->getTerminator();
604         int Successors = isa<ReturnInst>(TI) ? 1 : TI->getNumSuccessors();
605         if (Successors) {
606           if (Successors == 1) {
607             IRBuilder<> Builder(BB->getFirstInsertionPt());
608             Value *Counter = Builder.CreateConstInBoundsGEP2_64(Counters, 0,
609                                                                 Edge);
610             Value *Count = Builder.CreateLoad(Counter);
611             Count = Builder.CreateAdd(Count, Builder.getInt64(1));
612             Builder.CreateStore(Count, Counter);
613           } else if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
614             IRBuilder<> Builder(BI);
615             Value *Sel = Builder.CreateSelect(BI->getCondition(),
616                                               Builder.getInt64(Edge),
617                                               Builder.getInt64(Edge + 1));
618             SmallVector<Value *, 2> Idx;
619             Idx.push_back(Builder.getInt64(0));
620             Idx.push_back(Sel);
621             Value *Counter = Builder.CreateInBoundsGEP(Counters->getValueType(),
622                                                        Counters, Idx);
623             Value *Count = Builder.CreateLoad(Counter);
624             Count = Builder.CreateAdd(Count, Builder.getInt64(1));
625             Builder.CreateStore(Count, Counter);
626           } else {
627             ComplexEdgePreds.insert(BB);
628             for (int i = 0; i != Successors; ++i)
629               ComplexEdgeSuccs.insert(TI->getSuccessor(i));
630           }
631 
632           Edge += Successors;
633         }
634       }
635 
636       if (!ComplexEdgePreds.empty()) {
637         GlobalVariable *EdgeTable =
638           buildEdgeLookupTable(F, Counters,
639                                ComplexEdgePreds, ComplexEdgeSuccs);
640         GlobalVariable *EdgeState = getEdgeStateValue();
641 
642         for (int i = 0, e = ComplexEdgePreds.size(); i != e; ++i) {
643           IRBuilder<> Builder(ComplexEdgePreds[i + 1]->getFirstInsertionPt());
644           Builder.CreateStore(Builder.getInt32(i), EdgeState);
645         }
646 
647         for (int i = 0, e = ComplexEdgeSuccs.size(); i != e; ++i) {
648           // Call runtime to perform increment.
649           IRBuilder<> Builder(ComplexEdgeSuccs[i+1]->getFirstInsertionPt());
650           Value *CounterPtrArray =
651             Builder.CreateConstInBoundsGEP2_64(EdgeTable, 0,
652                                                i * ComplexEdgePreds.size());
653 
654           // Build code to increment the counter.
655           InsertIndCounterIncrCode = true;
656           Builder.CreateCall2(getIncrementIndirectCounterFunc(),
657                               EdgeState, CounterPtrArray);
658         }
659       }
660     }
661 
662     Function *WriteoutF = insertCounterWriteout(CountersBySP);
663     Function *FlushF = insertFlush(CountersBySP);
664 
665     // Create a small bit of code that registers the "__llvm_gcov_writeout" to
666     // be executed at exit and the "__llvm_gcov_flush" function to be executed
667     // when "__gcov_flush" is called.
668     FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
669     Function *F = Function::Create(FTy, GlobalValue::InternalLinkage,
670                                    "__llvm_gcov_init", M);
671     F->setUnnamedAddr(true);
672     F->setLinkage(GlobalValue::InternalLinkage);
673     F->addFnAttr(Attribute::NoInline);
674     if (Options.NoRedZone)
675       F->addFnAttr(Attribute::NoRedZone);
676 
677     BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", F);
678     IRBuilder<> Builder(BB);
679 
680     FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
681     Type *Params[] = {
682       PointerType::get(FTy, 0),
683       PointerType::get(FTy, 0)
684     };
685     FTy = FunctionType::get(Builder.getVoidTy(), Params, false);
686 
687     // Initialize the environment and register the local writeout and flush
688     // functions.
689     Constant *GCOVInit = M->getOrInsertFunction("llvm_gcov_init", FTy);
690     Builder.CreateCall2(GCOVInit, WriteoutF, FlushF);
691     Builder.CreateRetVoid();
692 
693     appendToGlobalCtors(*M, F, 0);
694   }
695 
696   if (InsertIndCounterIncrCode)
697     insertIndirectCounterIncrement();
698 
699   return Result;
700 }
701 
702 // All edges with successors that aren't branches are "complex", because it
703 // requires complex logic to pick which counter to update.
buildEdgeLookupTable(Function * F,GlobalVariable * Counters,const UniqueVector<BasicBlock * > & Preds,const UniqueVector<BasicBlock * > & Succs)704 GlobalVariable *GCOVProfiler::buildEdgeLookupTable(
705     Function *F,
706     GlobalVariable *Counters,
707     const UniqueVector<BasicBlock *> &Preds,
708     const UniqueVector<BasicBlock *> &Succs) {
709   // TODO: support invoke, threads. We rely on the fact that nothing can modify
710   // the whole-Module pred edge# between the time we set it and the time we next
711   // read it. Threads and invoke make this untrue.
712 
713   // emit [(succs * preds) x i64*], logically [succ x [pred x i64*]].
714   size_t TableSize = Succs.size() * Preds.size();
715   Type *Int64PtrTy = Type::getInt64PtrTy(*Ctx);
716   ArrayType *EdgeTableTy = ArrayType::get(Int64PtrTy, TableSize);
717 
718   std::unique_ptr<Constant * []> EdgeTable(new Constant *[TableSize]);
719   Constant *NullValue = Constant::getNullValue(Int64PtrTy);
720   for (size_t i = 0; i != TableSize; ++i)
721     EdgeTable[i] = NullValue;
722 
723   unsigned Edge = 0;
724   for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
725     TerminatorInst *TI = BB->getTerminator();
726     int Successors = isa<ReturnInst>(TI) ? 1 : TI->getNumSuccessors();
727     if (Successors > 1 && !isa<BranchInst>(TI) && !isa<ReturnInst>(TI)) {
728       for (int i = 0; i != Successors; ++i) {
729         BasicBlock *Succ = TI->getSuccessor(i);
730         IRBuilder<> Builder(Succ);
731         Value *Counter = Builder.CreateConstInBoundsGEP2_64(Counters, 0,
732                                                             Edge + i);
733         EdgeTable[((Succs.idFor(Succ)-1) * Preds.size()) +
734                   (Preds.idFor(BB)-1)] = cast<Constant>(Counter);
735       }
736     }
737     Edge += Successors;
738   }
739 
740   GlobalVariable *EdgeTableGV =
741       new GlobalVariable(
742           *M, EdgeTableTy, true, GlobalValue::InternalLinkage,
743           ConstantArray::get(EdgeTableTy,
744                              makeArrayRef(&EdgeTable[0],TableSize)),
745           "__llvm_gcda_edge_table");
746   EdgeTableGV->setUnnamedAddr(true);
747   return EdgeTableGV;
748 }
749 
getStartFileFunc()750 Constant *GCOVProfiler::getStartFileFunc() {
751   Type *Args[] = {
752     Type::getInt8PtrTy(*Ctx),  // const char *orig_filename
753     Type::getInt8PtrTy(*Ctx),  // const char version[4]
754     Type::getInt32Ty(*Ctx),    // uint32_t checksum
755   };
756   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
757   return M->getOrInsertFunction("llvm_gcda_start_file", FTy);
758 }
759 
getIncrementIndirectCounterFunc()760 Constant *GCOVProfiler::getIncrementIndirectCounterFunc() {
761   Type *Int32Ty = Type::getInt32Ty(*Ctx);
762   Type *Int64Ty = Type::getInt64Ty(*Ctx);
763   Type *Args[] = {
764     Int32Ty->getPointerTo(),                // uint32_t *predecessor
765     Int64Ty->getPointerTo()->getPointerTo() // uint64_t **counters
766   };
767   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
768   return M->getOrInsertFunction("__llvm_gcov_indirect_counter_increment", FTy);
769 }
770 
getEmitFunctionFunc()771 Constant *GCOVProfiler::getEmitFunctionFunc() {
772   Type *Args[] = {
773     Type::getInt32Ty(*Ctx),    // uint32_t ident
774     Type::getInt8PtrTy(*Ctx),  // const char *function_name
775     Type::getInt32Ty(*Ctx),    // uint32_t func_checksum
776     Type::getInt8Ty(*Ctx),     // uint8_t use_extra_checksum
777     Type::getInt32Ty(*Ctx),    // uint32_t cfg_checksum
778   };
779   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
780   return M->getOrInsertFunction("llvm_gcda_emit_function", FTy);
781 }
782 
getEmitArcsFunc()783 Constant *GCOVProfiler::getEmitArcsFunc() {
784   Type *Args[] = {
785     Type::getInt32Ty(*Ctx),     // uint32_t num_counters
786     Type::getInt64PtrTy(*Ctx),  // uint64_t *counters
787   };
788   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
789   return M->getOrInsertFunction("llvm_gcda_emit_arcs", FTy);
790 }
791 
getSummaryInfoFunc()792 Constant *GCOVProfiler::getSummaryInfoFunc() {
793   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
794   return M->getOrInsertFunction("llvm_gcda_summary_info", FTy);
795 }
796 
getDeleteWriteoutFunctionListFunc()797 Constant *GCOVProfiler::getDeleteWriteoutFunctionListFunc() {
798   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
799   return M->getOrInsertFunction("llvm_delete_writeout_function_list", FTy);
800 }
801 
getDeleteFlushFunctionListFunc()802 Constant *GCOVProfiler::getDeleteFlushFunctionListFunc() {
803   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
804   return M->getOrInsertFunction("llvm_delete_flush_function_list", FTy);
805 }
806 
getEndFileFunc()807 Constant *GCOVProfiler::getEndFileFunc() {
808   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
809   return M->getOrInsertFunction("llvm_gcda_end_file", FTy);
810 }
811 
getEdgeStateValue()812 GlobalVariable *GCOVProfiler::getEdgeStateValue() {
813   GlobalVariable *GV = M->getGlobalVariable("__llvm_gcov_global_state_pred");
814   if (!GV) {
815     GV = new GlobalVariable(*M, Type::getInt32Ty(*Ctx), false,
816                             GlobalValue::InternalLinkage,
817                             ConstantInt::get(Type::getInt32Ty(*Ctx),
818                                              0xffffffff),
819                             "__llvm_gcov_global_state_pred");
820     GV->setUnnamedAddr(true);
821   }
822   return GV;
823 }
824 
insertCounterWriteout(ArrayRef<std::pair<GlobalVariable *,MDNode * >> CountersBySP)825 Function *GCOVProfiler::insertCounterWriteout(
826     ArrayRef<std::pair<GlobalVariable *, MDNode *> > CountersBySP) {
827   FunctionType *WriteoutFTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
828   Function *WriteoutF = M->getFunction("__llvm_gcov_writeout");
829   if (!WriteoutF)
830     WriteoutF = Function::Create(WriteoutFTy, GlobalValue::InternalLinkage,
831                                  "__llvm_gcov_writeout", M);
832   WriteoutF->setUnnamedAddr(true);
833   WriteoutF->addFnAttr(Attribute::NoInline);
834   if (Options.NoRedZone)
835     WriteoutF->addFnAttr(Attribute::NoRedZone);
836 
837   BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", WriteoutF);
838   IRBuilder<> Builder(BB);
839 
840   Constant *StartFile = getStartFileFunc();
841   Constant *EmitFunction = getEmitFunctionFunc();
842   Constant *EmitArcs = getEmitArcsFunc();
843   Constant *SummaryInfo = getSummaryInfoFunc();
844   Constant *EndFile = getEndFileFunc();
845 
846   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
847   if (CU_Nodes) {
848     for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
849       DICompileUnit CU = cast<MDCompileUnit>(CU_Nodes->getOperand(i));
850       std::string FilenameGcda = mangleName(CU, "gcda");
851       uint32_t CfgChecksum = FileChecksums.empty() ? 0 : FileChecksums[i];
852       Builder.CreateCall3(StartFile,
853                           Builder.CreateGlobalStringPtr(FilenameGcda),
854                           Builder.CreateGlobalStringPtr(ReversedVersion),
855                           Builder.getInt32(CfgChecksum));
856       for (unsigned j = 0, e = CountersBySP.size(); j != e; ++j) {
857         auto *SP = cast_or_null<MDSubprogram>(CountersBySP[j].second);
858         uint32_t FuncChecksum = Funcs.empty() ? 0 : Funcs[j]->getFuncChecksum();
859         Builder.CreateCall5(
860             EmitFunction, Builder.getInt32(j),
861             Options.FunctionNamesInData ?
862               Builder.CreateGlobalStringPtr(getFunctionName(SP)) :
863               Constant::getNullValue(Builder.getInt8PtrTy()),
864             Builder.getInt32(FuncChecksum),
865             Builder.getInt8(Options.UseCfgChecksum),
866             Builder.getInt32(CfgChecksum));
867 
868         GlobalVariable *GV = CountersBySP[j].first;
869         unsigned Arcs =
870           cast<ArrayType>(GV->getType()->getElementType())->getNumElements();
871         Builder.CreateCall2(EmitArcs,
872                             Builder.getInt32(Arcs),
873                             Builder.CreateConstGEP2_64(GV, 0, 0));
874       }
875       Builder.CreateCall(SummaryInfo);
876       Builder.CreateCall(EndFile);
877     }
878   }
879 
880   Builder.CreateRetVoid();
881   return WriteoutF;
882 }
883 
insertIndirectCounterIncrement()884 void GCOVProfiler::insertIndirectCounterIncrement() {
885   Function *Fn =
886     cast<Function>(GCOVProfiler::getIncrementIndirectCounterFunc());
887   Fn->setUnnamedAddr(true);
888   Fn->setLinkage(GlobalValue::InternalLinkage);
889   Fn->addFnAttr(Attribute::NoInline);
890   if (Options.NoRedZone)
891     Fn->addFnAttr(Attribute::NoRedZone);
892 
893   // Create basic blocks for function.
894   BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", Fn);
895   IRBuilder<> Builder(BB);
896 
897   BasicBlock *PredNotNegOne = BasicBlock::Create(*Ctx, "", Fn);
898   BasicBlock *CounterEnd = BasicBlock::Create(*Ctx, "", Fn);
899   BasicBlock *Exit = BasicBlock::Create(*Ctx, "exit", Fn);
900 
901   // uint32_t pred = *predecessor;
902   // if (pred == 0xffffffff) return;
903   Argument *Arg = Fn->arg_begin();
904   Arg->setName("predecessor");
905   Value *Pred = Builder.CreateLoad(Arg, "pred");
906   Value *Cond = Builder.CreateICmpEQ(Pred, Builder.getInt32(0xffffffff));
907   BranchInst::Create(Exit, PredNotNegOne, Cond, BB);
908 
909   Builder.SetInsertPoint(PredNotNegOne);
910 
911   // uint64_t *counter = counters[pred];
912   // if (!counter) return;
913   Value *ZExtPred = Builder.CreateZExt(Pred, Builder.getInt64Ty());
914   Arg = std::next(Fn->arg_begin());
915   Arg->setName("counters");
916   Value *GEP = Builder.CreateGEP(Type::getInt64PtrTy(*Ctx), Arg, ZExtPred);
917   Value *Counter = Builder.CreateLoad(GEP, "counter");
918   Cond = Builder.CreateICmpEQ(Counter,
919                               Constant::getNullValue(
920                                   Builder.getInt64Ty()->getPointerTo()));
921   Builder.CreateCondBr(Cond, Exit, CounterEnd);
922 
923   // ++*counter;
924   Builder.SetInsertPoint(CounterEnd);
925   Value *Add = Builder.CreateAdd(Builder.CreateLoad(Counter),
926                                  Builder.getInt64(1));
927   Builder.CreateStore(Add, Counter);
928   Builder.CreateBr(Exit);
929 
930   // Fill in the exit block.
931   Builder.SetInsertPoint(Exit);
932   Builder.CreateRetVoid();
933 }
934 
935 Function *GCOVProfiler::
insertFlush(ArrayRef<std::pair<GlobalVariable *,MDNode * >> CountersBySP)936 insertFlush(ArrayRef<std::pair<GlobalVariable*, MDNode*> > CountersBySP) {
937   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
938   Function *FlushF = M->getFunction("__llvm_gcov_flush");
939   if (!FlushF)
940     FlushF = Function::Create(FTy, GlobalValue::InternalLinkage,
941                               "__llvm_gcov_flush", M);
942   else
943     FlushF->setLinkage(GlobalValue::InternalLinkage);
944   FlushF->setUnnamedAddr(true);
945   FlushF->addFnAttr(Attribute::NoInline);
946   if (Options.NoRedZone)
947     FlushF->addFnAttr(Attribute::NoRedZone);
948 
949   BasicBlock *Entry = BasicBlock::Create(*Ctx, "entry", FlushF);
950 
951   // Write out the current counters.
952   Constant *WriteoutF = M->getFunction("__llvm_gcov_writeout");
953   assert(WriteoutF && "Need to create the writeout function first!");
954 
955   IRBuilder<> Builder(Entry);
956   Builder.CreateCall(WriteoutF);
957 
958   // Zero out the counters.
959   for (ArrayRef<std::pair<GlobalVariable *, MDNode *> >::iterator
960          I = CountersBySP.begin(), E = CountersBySP.end();
961        I != E; ++I) {
962     GlobalVariable *GV = I->first;
963     Constant *Null = Constant::getNullValue(GV->getType()->getElementType());
964     Builder.CreateStore(Null, GV);
965   }
966 
967   Type *RetTy = FlushF->getReturnType();
968   if (RetTy == Type::getVoidTy(*Ctx))
969     Builder.CreateRetVoid();
970   else if (RetTy->isIntegerTy())
971     // Used if __llvm_gcov_flush was implicitly declared.
972     Builder.CreateRet(ConstantInt::get(RetTy, 0));
973   else
974     report_fatal_error("invalid return type for __llvm_gcov_flush");
975 
976   return FlushF;
977 }
978