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(const DICompileUnit *CU, const char *NewStem);
130 
131     GCOVOptions Options;
132 
133     // Reversed, NUL-terminated copy of Options.Version.
134     char ReversedVersion[5];
135     // Checksum, produced by hash of EdgeDestinations
136     SmallVector<uint32_t, 4> FileChecksums;
137 
138     Module *M;
139     LLVMContext *Ctx;
140     SmallVector<std::unique_ptr<GCOVFunction>, 16> Funcs;
141     DenseMap<DISubprogram *, Function *> FnMap;
142   };
143 }
144 
145 char GCOVProfiler::ID = 0;
146 INITIALIZE_PASS(GCOVProfiler, "insert-gcov-profiling",
147                 "Insert instrumentation for GCOV profiling", false, false)
148 
createGCOVProfilerPass(const GCOVOptions & Options)149 ModulePass *llvm::createGCOVProfilerPass(const GCOVOptions &Options) {
150   return new GCOVProfiler(Options);
151 }
152 
getFunctionName(const DISubprogram * SP)153 static StringRef getFunctionName(const DISubprogram *SP) {
154   if (!SP->getLinkageName().empty())
155     return SP->getLinkageName();
156   return SP->getName();
157 }
158 
159 namespace {
160   class GCOVRecord {
161    protected:
162     static const char *const LinesTag;
163     static const char *const FunctionTag;
164     static const char *const BlockTag;
165     static const char *const EdgeTag;
166 
167     GCOVRecord() = default;
168 
writeBytes(const char * Bytes,int Size)169     void writeBytes(const char *Bytes, int Size) {
170       os->write(Bytes, Size);
171     }
172 
write(uint32_t i)173     void write(uint32_t i) {
174       writeBytes(reinterpret_cast<char*>(&i), 4);
175     }
176 
177     // Returns the length measured in 4-byte blocks that will be used to
178     // represent this string in a GCOV file
lengthOfGCOVString(StringRef s)179     static unsigned lengthOfGCOVString(StringRef s) {
180       // A GCOV string is a length, followed by a NUL, then between 0 and 3 NULs
181       // padding out to the next 4-byte word. The length is measured in 4-byte
182       // words including padding, not bytes of actual string.
183       return (s.size() / 4) + 1;
184     }
185 
writeGCOVString(StringRef s)186     void writeGCOVString(StringRef s) {
187       uint32_t Len = lengthOfGCOVString(s);
188       write(Len);
189       writeBytes(s.data(), s.size());
190 
191       // Write 1 to 4 bytes of NUL padding.
192       assert((unsigned)(4 - (s.size() % 4)) > 0);
193       assert((unsigned)(4 - (s.size() % 4)) <= 4);
194       writeBytes("\0\0\0\0", 4 - (s.size() % 4));
195     }
196 
197     raw_ostream *os;
198   };
199   const char *const GCOVRecord::LinesTag = "\0\0\x45\x01";
200   const char *const GCOVRecord::FunctionTag = "\0\0\0\1";
201   const char *const GCOVRecord::BlockTag = "\0\0\x41\x01";
202   const char *const GCOVRecord::EdgeTag = "\0\0\x43\x01";
203 
204   class GCOVFunction;
205   class GCOVBlock;
206 
207   // Constructed only by requesting it from a GCOVBlock, this object stores a
208   // list of line numbers and a single filename, representing lines that belong
209   // to the block.
210   class GCOVLines : public GCOVRecord {
211    public:
addLine(uint32_t Line)212     void addLine(uint32_t Line) {
213       assert(Line != 0 && "Line zero is not a valid real line number.");
214       Lines.push_back(Line);
215     }
216 
length() const217     uint32_t length() const {
218       // Here 2 = 1 for string length + 1 for '0' id#.
219       return lengthOfGCOVString(Filename) + 2 + Lines.size();
220     }
221 
writeOut()222     void writeOut() {
223       write(0);
224       writeGCOVString(Filename);
225       for (int i = 0, e = Lines.size(); i != e; ++i)
226         write(Lines[i]);
227     }
228 
GCOVLines(StringRef F,raw_ostream * os)229     GCOVLines(StringRef F, raw_ostream *os)
230       : Filename(F) {
231       this->os = os;
232     }
233 
234    private:
235     StringRef Filename;
236     SmallVector<uint32_t, 32> Lines;
237   };
238 
239 
240   // Represent a basic block in GCOV. Each block has a unique number in the
241   // function, number of lines belonging to each block, and a set of edges to
242   // other blocks.
243   class GCOVBlock : public GCOVRecord {
244    public:
getFile(StringRef Filename)245     GCOVLines &getFile(StringRef Filename) {
246       GCOVLines *&Lines = LinesByFile[Filename];
247       if (!Lines) {
248         Lines = new GCOVLines(Filename, os);
249       }
250       return *Lines;
251     }
252 
addEdge(GCOVBlock & Successor)253     void addEdge(GCOVBlock &Successor) {
254       OutEdges.push_back(&Successor);
255     }
256 
writeOut()257     void writeOut() {
258       uint32_t Len = 3;
259       SmallVector<StringMapEntry<GCOVLines *> *, 32> SortedLinesByFile;
260       for (StringMap<GCOVLines *>::iterator I = LinesByFile.begin(),
261                E = LinesByFile.end(); I != E; ++I) {
262         Len += I->second->length();
263         SortedLinesByFile.push_back(&*I);
264       }
265 
266       writeBytes(LinesTag, 4);
267       write(Len);
268       write(Number);
269 
270       std::sort(SortedLinesByFile.begin(), SortedLinesByFile.end(),
271                 [](StringMapEntry<GCOVLines *> *LHS,
272                    StringMapEntry<GCOVLines *> *RHS) {
273         return LHS->getKey() < RHS->getKey();
274       });
275       for (SmallVectorImpl<StringMapEntry<GCOVLines *> *>::iterator
276                I = SortedLinesByFile.begin(), E = SortedLinesByFile.end();
277            I != E; ++I)
278         (*I)->getValue()->writeOut();
279       write(0);
280       write(0);
281     }
282 
~GCOVBlock()283     ~GCOVBlock() {
284       DeleteContainerSeconds(LinesByFile);
285     }
286 
GCOVBlock(const GCOVBlock & RHS)287     GCOVBlock(const GCOVBlock &RHS) : GCOVRecord(RHS), Number(RHS.Number) {
288       // Only allow copy before edges and lines have been added. After that,
289       // there are inter-block pointers (eg: edges) that won't take kindly to
290       // blocks being copied or moved around.
291       assert(LinesByFile.empty());
292       assert(OutEdges.empty());
293     }
294 
295    private:
296     friend class GCOVFunction;
297 
GCOVBlock(uint32_t Number,raw_ostream * os)298     GCOVBlock(uint32_t Number, raw_ostream *os)
299         : Number(Number) {
300       this->os = os;
301     }
302 
303     uint32_t Number;
304     StringMap<GCOVLines *> LinesByFile;
305     SmallVector<GCOVBlock *, 4> OutEdges;
306   };
307 
308   // A function has a unique identifier, a checksum (we leave as zero) and a
309   // set of blocks and a map of edges between blocks. This is the only GCOV
310   // object users can construct, the blocks and lines will be rooted here.
311   class GCOVFunction : public GCOVRecord {
312    public:
GCOVFunction(const DISubprogram * SP,Function * F,raw_ostream * os,uint32_t Ident,bool UseCfgChecksum,bool ExitBlockBeforeBody)313      GCOVFunction(const DISubprogram *SP, Function *F, raw_ostream *os,
314                   uint32_t Ident, bool UseCfgChecksum, bool ExitBlockBeforeBody)
315          : SP(SP), Ident(Ident), UseCfgChecksum(UseCfgChecksum), CfgChecksum(0),
316            ReturnBlock(1, os) {
317       this->os = os;
318 
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 (BasicBlock &I : *F) {
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 (BasicBlock &I : *F) {
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 (BasicBlock &I : *F)
409         getBlock(&I).writeOut();
410     }
411 
412    private:
413      const DISubprogram *SP;
414     uint32_t Ident;
415     uint32_t FuncChecksum;
416     bool UseCfgChecksum;
417     uint32_t CfgChecksum;
418     DenseMap<BasicBlock *, GCOVBlock> Blocks;
419     GCOVBlock ReturnBlock;
420   };
421 }
422 
mangleName(const DICompileUnit * CU,const char * NewStem)423 std::string GCOVProfiler::mangleName(const DICompileUnit *CU,
424                                      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   FnMap.clear();
454   for (Function &F : M) {
455     if (DISubprogram *SP = F.getSubprogram())
456       FnMap[SP] = &F;
457   }
458 
459   if (Options.EmitNotes) emitProfileNotes();
460   if (Options.EmitData) return emitProfileArcs();
461   return false;
462 }
463 
functionHasLines(Function * F)464 static bool functionHasLines(Function *F) {
465   // Check whether this function actually has any source lines. Not only
466   // do these waste space, they also can crash gcov.
467   for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
468     for (BasicBlock::iterator I = BB->begin(), IE = BB->end();
469          I != IE; ++I) {
470       // Debug intrinsic locations correspond to the location of the
471       // declaration, not necessarily any statements or expressions.
472       if (isa<DbgInfoIntrinsic>(I)) continue;
473 
474       const DebugLoc &Loc = I->getDebugLoc();
475       if (!Loc)
476         continue;
477 
478       // Artificial lines such as calls to the global constructors.
479       if (Loc.getLine() == 0) continue;
480 
481       return true;
482     }
483   }
484   return false;
485 }
486 
emitProfileNotes()487 void GCOVProfiler::emitProfileNotes() {
488   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
489   if (!CU_Nodes) return;
490 
491   for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
492     // Each compile unit gets its own .gcno file. This means that whether we run
493     // this pass over the original .o's as they're produced, or run it after
494     // LTO, we'll generate the same .gcno files.
495 
496     auto *CU = cast<DICompileUnit>(CU_Nodes->getOperand(i));
497     std::error_code EC;
498     raw_fd_ostream out(mangleName(CU, "gcno"), EC, sys::fs::F_None);
499     std::string EdgeDestinations;
500 
501     unsigned FunctionIdent = 0;
502     for (auto *SP : CU->getSubprograms()) {
503       Function *F = FnMap[SP];
504       if (!F) continue;
505       if (!functionHasLines(F)) continue;
506 
507       // gcov expects every function to start with an entry block that has a
508       // single successor, so split the entry block to make sure of that.
509       BasicBlock &EntryBlock = F->getEntryBlock();
510       BasicBlock::iterator It = EntryBlock.begin();
511       while (isa<AllocaInst>(*It) || isa<DbgInfoIntrinsic>(*It))
512         ++It;
513       EntryBlock.splitBasicBlock(It);
514 
515       Funcs.push_back(make_unique<GCOVFunction>(SP, F, &out, FunctionIdent++,
516                                                 Options.UseCfgChecksum,
517                                                 Options.ExitBlockBeforeBody));
518       GCOVFunction &Func = *Funcs.back();
519 
520       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
521         GCOVBlock &Block = Func.getBlock(&*BB);
522         TerminatorInst *TI = BB->getTerminator();
523         if (int successors = TI->getNumSuccessors()) {
524           for (int i = 0; i != successors; ++i) {
525             Block.addEdge(Func.getBlock(TI->getSuccessor(i)));
526           }
527         } else if (isa<ReturnInst>(TI)) {
528           Block.addEdge(Func.getReturnBlock());
529         }
530 
531         uint32_t Line = 0;
532         for (BasicBlock::iterator I = BB->begin(), IE = BB->end();
533              I != IE; ++I) {
534           // Debug intrinsic locations correspond to the location of the
535           // declaration, not necessarily any statements or expressions.
536           if (isa<DbgInfoIntrinsic>(I)) continue;
537 
538           const DebugLoc &Loc = I->getDebugLoc();
539           if (!Loc)
540             continue;
541 
542           // Artificial lines such as calls to the global constructors.
543           if (Loc.getLine() == 0) continue;
544 
545           if (Line == Loc.getLine()) continue;
546           Line = Loc.getLine();
547           if (SP != getDISubprogram(Loc.getScope()))
548             continue;
549 
550           GCOVLines &Lines = Block.getFile(SP->getFilename());
551           Lines.addLine(Loc.getLine());
552         }
553       }
554       EdgeDestinations += Func.getEdgeDestinations();
555     }
556 
557     FileChecksums.push_back(hash_value(EdgeDestinations));
558     out.write("oncg", 4);
559     out.write(ReversedVersion, 4);
560     out.write(reinterpret_cast<char*>(&FileChecksums.back()), 4);
561 
562     for (auto &Func : Funcs) {
563       Func->setCfgChecksum(FileChecksums.back());
564       Func->writeOut();
565     }
566 
567     out.write("\0\0\0\0\0\0\0\0", 8);  // EOF
568     out.close();
569   }
570 }
571 
emitProfileArcs()572 bool GCOVProfiler::emitProfileArcs() {
573   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
574   if (!CU_Nodes) return false;
575 
576   bool Result = false;
577   bool InsertIndCounterIncrCode = false;
578   for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
579     auto *CU = cast<DICompileUnit>(CU_Nodes->getOperand(i));
580     SmallVector<std::pair<GlobalVariable *, MDNode *>, 8> CountersBySP;
581     for (auto *SP : CU->getSubprograms()) {
582       Function *F = FnMap[SP];
583       if (!F) continue;
584       if (!functionHasLines(F)) continue;
585       if (!Result) Result = true;
586       unsigned Edges = 0;
587       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
588         TerminatorInst *TI = BB->getTerminator();
589         if (isa<ReturnInst>(TI))
590           ++Edges;
591         else
592           Edges += TI->getNumSuccessors();
593       }
594 
595       ArrayType *CounterTy =
596         ArrayType::get(Type::getInt64Ty(*Ctx), Edges);
597       GlobalVariable *Counters =
598         new GlobalVariable(*M, CounterTy, false,
599                            GlobalValue::InternalLinkage,
600                            Constant::getNullValue(CounterTy),
601                            "__llvm_gcov_ctr");
602       CountersBySP.push_back(std::make_pair(Counters, SP));
603 
604       UniqueVector<BasicBlock *> ComplexEdgePreds;
605       UniqueVector<BasicBlock *> ComplexEdgeSuccs;
606 
607       unsigned Edge = 0;
608       for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
609         TerminatorInst *TI = BB->getTerminator();
610         int Successors = isa<ReturnInst>(TI) ? 1 : TI->getNumSuccessors();
611         if (Successors) {
612           if (Successors == 1) {
613             IRBuilder<> Builder(&*BB->getFirstInsertionPt());
614             Value *Counter = Builder.CreateConstInBoundsGEP2_64(Counters, 0,
615                                                                 Edge);
616             Value *Count = Builder.CreateLoad(Counter);
617             Count = Builder.CreateAdd(Count, Builder.getInt64(1));
618             Builder.CreateStore(Count, Counter);
619           } else if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
620             IRBuilder<> Builder(BI);
621             Value *Sel = Builder.CreateSelect(BI->getCondition(),
622                                               Builder.getInt64(Edge),
623                                               Builder.getInt64(Edge + 1));
624             SmallVector<Value *, 2> Idx;
625             Idx.push_back(Builder.getInt64(0));
626             Idx.push_back(Sel);
627             Value *Counter = Builder.CreateInBoundsGEP(Counters->getValueType(),
628                                                        Counters, Idx);
629             Value *Count = Builder.CreateLoad(Counter);
630             Count = Builder.CreateAdd(Count, Builder.getInt64(1));
631             Builder.CreateStore(Count, Counter);
632           } else {
633             ComplexEdgePreds.insert(&*BB);
634             for (int i = 0; i != Successors; ++i)
635               ComplexEdgeSuccs.insert(TI->getSuccessor(i));
636           }
637 
638           Edge += Successors;
639         }
640       }
641 
642       if (!ComplexEdgePreds.empty()) {
643         GlobalVariable *EdgeTable =
644           buildEdgeLookupTable(F, Counters,
645                                ComplexEdgePreds, ComplexEdgeSuccs);
646         GlobalVariable *EdgeState = getEdgeStateValue();
647 
648         for (int i = 0, e = ComplexEdgePreds.size(); i != e; ++i) {
649           IRBuilder<> Builder(&*ComplexEdgePreds[i + 1]->getFirstInsertionPt());
650           Builder.CreateStore(Builder.getInt32(i), EdgeState);
651         }
652 
653         for (int i = 0, e = ComplexEdgeSuccs.size(); i != e; ++i) {
654           // Call runtime to perform increment.
655           IRBuilder<> Builder(&*ComplexEdgeSuccs[i + 1]->getFirstInsertionPt());
656           Value *CounterPtrArray =
657             Builder.CreateConstInBoundsGEP2_64(EdgeTable, 0,
658                                                i * ComplexEdgePreds.size());
659 
660           // Build code to increment the counter.
661           InsertIndCounterIncrCode = true;
662           Builder.CreateCall(getIncrementIndirectCounterFunc(),
663                              {EdgeState, CounterPtrArray});
664         }
665       }
666     }
667 
668     Function *WriteoutF = insertCounterWriteout(CountersBySP);
669     Function *FlushF = insertFlush(CountersBySP);
670 
671     // Create a small bit of code that registers the "__llvm_gcov_writeout" to
672     // be executed at exit and the "__llvm_gcov_flush" function to be executed
673     // when "__gcov_flush" is called.
674     FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
675     Function *F = Function::Create(FTy, GlobalValue::InternalLinkage,
676                                    "__llvm_gcov_init", M);
677     F->setUnnamedAddr(true);
678     F->setLinkage(GlobalValue::InternalLinkage);
679     F->addFnAttr(Attribute::NoInline);
680     if (Options.NoRedZone)
681       F->addFnAttr(Attribute::NoRedZone);
682 
683     BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", F);
684     IRBuilder<> Builder(BB);
685 
686     FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
687     Type *Params[] = {
688       PointerType::get(FTy, 0),
689       PointerType::get(FTy, 0)
690     };
691     FTy = FunctionType::get(Builder.getVoidTy(), Params, false);
692 
693     // Initialize the environment and register the local writeout and flush
694     // functions.
695     Constant *GCOVInit = M->getOrInsertFunction("llvm_gcov_init", FTy);
696     Builder.CreateCall(GCOVInit, {WriteoutF, FlushF});
697     Builder.CreateRetVoid();
698 
699     appendToGlobalCtors(*M, F, 0);
700   }
701 
702   if (InsertIndCounterIncrCode)
703     insertIndirectCounterIncrement();
704 
705   return Result;
706 }
707 
708 // All edges with successors that aren't branches are "complex", because it
709 // requires complex logic to pick which counter to update.
buildEdgeLookupTable(Function * F,GlobalVariable * Counters,const UniqueVector<BasicBlock * > & Preds,const UniqueVector<BasicBlock * > & Succs)710 GlobalVariable *GCOVProfiler::buildEdgeLookupTable(
711     Function *F,
712     GlobalVariable *Counters,
713     const UniqueVector<BasicBlock *> &Preds,
714     const UniqueVector<BasicBlock *> &Succs) {
715   // TODO: support invoke, threads. We rely on the fact that nothing can modify
716   // the whole-Module pred edge# between the time we set it and the time we next
717   // read it. Threads and invoke make this untrue.
718 
719   // emit [(succs * preds) x i64*], logically [succ x [pred x i64*]].
720   size_t TableSize = Succs.size() * Preds.size();
721   Type *Int64PtrTy = Type::getInt64PtrTy(*Ctx);
722   ArrayType *EdgeTableTy = ArrayType::get(Int64PtrTy, TableSize);
723 
724   std::unique_ptr<Constant * []> EdgeTable(new Constant *[TableSize]);
725   Constant *NullValue = Constant::getNullValue(Int64PtrTy);
726   for (size_t i = 0; i != TableSize; ++i)
727     EdgeTable[i] = NullValue;
728 
729   unsigned Edge = 0;
730   for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
731     TerminatorInst *TI = BB->getTerminator();
732     int Successors = isa<ReturnInst>(TI) ? 1 : TI->getNumSuccessors();
733     if (Successors > 1 && !isa<BranchInst>(TI) && !isa<ReturnInst>(TI)) {
734       for (int i = 0; i != Successors; ++i) {
735         BasicBlock *Succ = TI->getSuccessor(i);
736         IRBuilder<> Builder(Succ);
737         Value *Counter = Builder.CreateConstInBoundsGEP2_64(Counters, 0,
738                                                             Edge + i);
739         EdgeTable[((Succs.idFor(Succ) - 1) * Preds.size()) +
740                   (Preds.idFor(&*BB) - 1)] = cast<Constant>(Counter);
741       }
742     }
743     Edge += Successors;
744   }
745 
746   GlobalVariable *EdgeTableGV =
747       new GlobalVariable(
748           *M, EdgeTableTy, true, GlobalValue::InternalLinkage,
749           ConstantArray::get(EdgeTableTy,
750                              makeArrayRef(&EdgeTable[0],TableSize)),
751           "__llvm_gcda_edge_table");
752   EdgeTableGV->setUnnamedAddr(true);
753   return EdgeTableGV;
754 }
755 
getStartFileFunc()756 Constant *GCOVProfiler::getStartFileFunc() {
757   Type *Args[] = {
758     Type::getInt8PtrTy(*Ctx),  // const char *orig_filename
759     Type::getInt8PtrTy(*Ctx),  // const char version[4]
760     Type::getInt32Ty(*Ctx),    // uint32_t checksum
761   };
762   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
763   return M->getOrInsertFunction("llvm_gcda_start_file", FTy);
764 }
765 
getIncrementIndirectCounterFunc()766 Constant *GCOVProfiler::getIncrementIndirectCounterFunc() {
767   Type *Int32Ty = Type::getInt32Ty(*Ctx);
768   Type *Int64Ty = Type::getInt64Ty(*Ctx);
769   Type *Args[] = {
770     Int32Ty->getPointerTo(),                // uint32_t *predecessor
771     Int64Ty->getPointerTo()->getPointerTo() // uint64_t **counters
772   };
773   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
774   return M->getOrInsertFunction("__llvm_gcov_indirect_counter_increment", FTy);
775 }
776 
getEmitFunctionFunc()777 Constant *GCOVProfiler::getEmitFunctionFunc() {
778   Type *Args[] = {
779     Type::getInt32Ty(*Ctx),    // uint32_t ident
780     Type::getInt8PtrTy(*Ctx),  // const char *function_name
781     Type::getInt32Ty(*Ctx),    // uint32_t func_checksum
782     Type::getInt8Ty(*Ctx),     // uint8_t use_extra_checksum
783     Type::getInt32Ty(*Ctx),    // uint32_t cfg_checksum
784   };
785   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
786   return M->getOrInsertFunction("llvm_gcda_emit_function", FTy);
787 }
788 
getEmitArcsFunc()789 Constant *GCOVProfiler::getEmitArcsFunc() {
790   Type *Args[] = {
791     Type::getInt32Ty(*Ctx),     // uint32_t num_counters
792     Type::getInt64PtrTy(*Ctx),  // uint64_t *counters
793   };
794   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
795   return M->getOrInsertFunction("llvm_gcda_emit_arcs", FTy);
796 }
797 
getSummaryInfoFunc()798 Constant *GCOVProfiler::getSummaryInfoFunc() {
799   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
800   return M->getOrInsertFunction("llvm_gcda_summary_info", FTy);
801 }
802 
getDeleteWriteoutFunctionListFunc()803 Constant *GCOVProfiler::getDeleteWriteoutFunctionListFunc() {
804   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
805   return M->getOrInsertFunction("llvm_delete_writeout_function_list", FTy);
806 }
807 
getDeleteFlushFunctionListFunc()808 Constant *GCOVProfiler::getDeleteFlushFunctionListFunc() {
809   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
810   return M->getOrInsertFunction("llvm_delete_flush_function_list", FTy);
811 }
812 
getEndFileFunc()813 Constant *GCOVProfiler::getEndFileFunc() {
814   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
815   return M->getOrInsertFunction("llvm_gcda_end_file", FTy);
816 }
817 
getEdgeStateValue()818 GlobalVariable *GCOVProfiler::getEdgeStateValue() {
819   GlobalVariable *GV = M->getGlobalVariable("__llvm_gcov_global_state_pred");
820   if (!GV) {
821     GV = new GlobalVariable(*M, Type::getInt32Ty(*Ctx), false,
822                             GlobalValue::InternalLinkage,
823                             ConstantInt::get(Type::getInt32Ty(*Ctx),
824                                              0xffffffff),
825                             "__llvm_gcov_global_state_pred");
826     GV->setUnnamedAddr(true);
827   }
828   return GV;
829 }
830 
insertCounterWriteout(ArrayRef<std::pair<GlobalVariable *,MDNode * >> CountersBySP)831 Function *GCOVProfiler::insertCounterWriteout(
832     ArrayRef<std::pair<GlobalVariable *, MDNode *> > CountersBySP) {
833   FunctionType *WriteoutFTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
834   Function *WriteoutF = M->getFunction("__llvm_gcov_writeout");
835   if (!WriteoutF)
836     WriteoutF = Function::Create(WriteoutFTy, GlobalValue::InternalLinkage,
837                                  "__llvm_gcov_writeout", M);
838   WriteoutF->setUnnamedAddr(true);
839   WriteoutF->addFnAttr(Attribute::NoInline);
840   if (Options.NoRedZone)
841     WriteoutF->addFnAttr(Attribute::NoRedZone);
842 
843   BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", WriteoutF);
844   IRBuilder<> Builder(BB);
845 
846   Constant *StartFile = getStartFileFunc();
847   Constant *EmitFunction = getEmitFunctionFunc();
848   Constant *EmitArcs = getEmitArcsFunc();
849   Constant *SummaryInfo = getSummaryInfoFunc();
850   Constant *EndFile = getEndFileFunc();
851 
852   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
853   if (CU_Nodes) {
854     for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
855       auto *CU = cast<DICompileUnit>(CU_Nodes->getOperand(i));
856       std::string FilenameGcda = mangleName(CU, "gcda");
857       uint32_t CfgChecksum = FileChecksums.empty() ? 0 : FileChecksums[i];
858       Builder.CreateCall(StartFile,
859                          {Builder.CreateGlobalStringPtr(FilenameGcda),
860                           Builder.CreateGlobalStringPtr(ReversedVersion),
861                           Builder.getInt32(CfgChecksum)});
862       for (unsigned j = 0, e = CountersBySP.size(); j != e; ++j) {
863         auto *SP = cast_or_null<DISubprogram>(CountersBySP[j].second);
864         uint32_t FuncChecksum = Funcs.empty() ? 0 : Funcs[j]->getFuncChecksum();
865         Builder.CreateCall(
866             EmitFunction,
867             {Builder.getInt32(j),
868              Options.FunctionNamesInData
869                  ? Builder.CreateGlobalStringPtr(getFunctionName(SP))
870                  : Constant::getNullValue(Builder.getInt8PtrTy()),
871              Builder.getInt32(FuncChecksum),
872              Builder.getInt8(Options.UseCfgChecksum),
873              Builder.getInt32(CfgChecksum)});
874 
875         GlobalVariable *GV = CountersBySP[j].first;
876         unsigned Arcs =
877           cast<ArrayType>(GV->getType()->getElementType())->getNumElements();
878         Builder.CreateCall(EmitArcs, {Builder.getInt32(Arcs),
879                                       Builder.CreateConstGEP2_64(GV, 0, 0)});
880       }
881       Builder.CreateCall(SummaryInfo, {});
882       Builder.CreateCall(EndFile, {});
883     }
884   }
885 
886   Builder.CreateRetVoid();
887   return WriteoutF;
888 }
889 
insertIndirectCounterIncrement()890 void GCOVProfiler::insertIndirectCounterIncrement() {
891   Function *Fn =
892     cast<Function>(GCOVProfiler::getIncrementIndirectCounterFunc());
893   Fn->setUnnamedAddr(true);
894   Fn->setLinkage(GlobalValue::InternalLinkage);
895   Fn->addFnAttr(Attribute::NoInline);
896   if (Options.NoRedZone)
897     Fn->addFnAttr(Attribute::NoRedZone);
898 
899   // Create basic blocks for function.
900   BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", Fn);
901   IRBuilder<> Builder(BB);
902 
903   BasicBlock *PredNotNegOne = BasicBlock::Create(*Ctx, "", Fn);
904   BasicBlock *CounterEnd = BasicBlock::Create(*Ctx, "", Fn);
905   BasicBlock *Exit = BasicBlock::Create(*Ctx, "exit", Fn);
906 
907   // uint32_t pred = *predecessor;
908   // if (pred == 0xffffffff) return;
909   Argument *Arg = &*Fn->arg_begin();
910   Arg->setName("predecessor");
911   Value *Pred = Builder.CreateLoad(Arg, "pred");
912   Value *Cond = Builder.CreateICmpEQ(Pred, Builder.getInt32(0xffffffff));
913   BranchInst::Create(Exit, PredNotNegOne, Cond, BB);
914 
915   Builder.SetInsertPoint(PredNotNegOne);
916 
917   // uint64_t *counter = counters[pred];
918   // if (!counter) return;
919   Value *ZExtPred = Builder.CreateZExt(Pred, Builder.getInt64Ty());
920   Arg = &*std::next(Fn->arg_begin());
921   Arg->setName("counters");
922   Value *GEP = Builder.CreateGEP(Type::getInt64PtrTy(*Ctx), Arg, ZExtPred);
923   Value *Counter = Builder.CreateLoad(GEP, "counter");
924   Cond = Builder.CreateICmpEQ(Counter,
925                               Constant::getNullValue(
926                                   Builder.getInt64Ty()->getPointerTo()));
927   Builder.CreateCondBr(Cond, Exit, CounterEnd);
928 
929   // ++*counter;
930   Builder.SetInsertPoint(CounterEnd);
931   Value *Add = Builder.CreateAdd(Builder.CreateLoad(Counter),
932                                  Builder.getInt64(1));
933   Builder.CreateStore(Add, Counter);
934   Builder.CreateBr(Exit);
935 
936   // Fill in the exit block.
937   Builder.SetInsertPoint(Exit);
938   Builder.CreateRetVoid();
939 }
940 
941 Function *GCOVProfiler::
insertFlush(ArrayRef<std::pair<GlobalVariable *,MDNode * >> CountersBySP)942 insertFlush(ArrayRef<std::pair<GlobalVariable*, MDNode*> > CountersBySP) {
943   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
944   Function *FlushF = M->getFunction("__llvm_gcov_flush");
945   if (!FlushF)
946     FlushF = Function::Create(FTy, GlobalValue::InternalLinkage,
947                               "__llvm_gcov_flush", M);
948   else
949     FlushF->setLinkage(GlobalValue::InternalLinkage);
950   FlushF->setUnnamedAddr(true);
951   FlushF->addFnAttr(Attribute::NoInline);
952   if (Options.NoRedZone)
953     FlushF->addFnAttr(Attribute::NoRedZone);
954 
955   BasicBlock *Entry = BasicBlock::Create(*Ctx, "entry", FlushF);
956 
957   // Write out the current counters.
958   Constant *WriteoutF = M->getFunction("__llvm_gcov_writeout");
959   assert(WriteoutF && "Need to create the writeout function first!");
960 
961   IRBuilder<> Builder(Entry);
962   Builder.CreateCall(WriteoutF, {});
963 
964   // Zero out the counters.
965   for (ArrayRef<std::pair<GlobalVariable *, MDNode *> >::iterator
966          I = CountersBySP.begin(), E = CountersBySP.end();
967        I != E; ++I) {
968     GlobalVariable *GV = I->first;
969     Constant *Null = Constant::getNullValue(GV->getType()->getElementType());
970     Builder.CreateStore(Null, GV);
971   }
972 
973   Type *RetTy = FlushF->getReturnType();
974   if (RetTy == Type::getVoidTy(*Ctx))
975     Builder.CreateRetVoid();
976   else if (RetTy->isIntegerTy())
977     // Used if __llvm_gcov_flush was implicitly declared.
978     Builder.CreateRet(ConstantInt::get(RetTy, 0));
979   else
980     report_fatal_error("invalid return type for __llvm_gcov_flush");
981 
982   return FlushF;
983 }
984