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/ADT/DenseMap.h"
18 #include "llvm/ADT/Hashing.h"
19 #include "llvm/ADT/STLExtras.h"
20 #include "llvm/ADT/Sequence.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/Analysis/EHPersonalities.h"
26 #include "llvm/Analysis/TargetLibraryInfo.h"
27 #include "llvm/IR/DebugInfo.h"
28 #include "llvm/IR/DebugLoc.h"
29 #include "llvm/IR/IRBuilder.h"
30 #include "llvm/IR/InstIterator.h"
31 #include "llvm/IR/Instructions.h"
32 #include "llvm/IR/IntrinsicInst.h"
33 #include "llvm/IR/Module.h"
34 #include "llvm/Pass.h"
35 #include "llvm/Support/CommandLine.h"
36 #include "llvm/Support/Debug.h"
37 #include "llvm/Support/FileSystem.h"
38 #include "llvm/Support/Path.h"
39 #include "llvm/Support/raw_ostream.h"
40 #include "llvm/Transforms/Instrumentation.h"
41 #include "llvm/Transforms/Instrumentation/GCOVProfiler.h"
42 #include "llvm/Transforms/Utils/ModuleUtils.h"
43 #include <algorithm>
44 #include <memory>
45 #include <string>
46 #include <utility>
47 using namespace llvm;
48 
49 #define DEBUG_TYPE "insert-gcov-profiling"
50 
51 static cl::opt<std::string>
52 DefaultGCOVVersion("default-gcov-version", cl::init("402*"), cl::Hidden,
53                    cl::ValueRequired);
54 static cl::opt<bool> DefaultExitBlockBeforeBody("gcov-exit-block-before-body",
55                                                 cl::init(false), cl::Hidden);
56 
57 GCOVOptions GCOVOptions::getDefault() {
58   GCOVOptions Options;
59   Options.EmitNotes = true;
60   Options.EmitData = true;
61   Options.UseCfgChecksum = false;
62   Options.NoRedZone = false;
63   Options.FunctionNamesInData = true;
64   Options.ExitBlockBeforeBody = DefaultExitBlockBeforeBody;
65 
66   if (DefaultGCOVVersion.size() != 4) {
67     llvm::report_fatal_error(std::string("Invalid -default-gcov-version: ") +
68                              DefaultGCOVVersion);
69   }
70   memcpy(Options.Version, DefaultGCOVVersion.c_str(), 4);
71   return Options;
72 }
73 
74 namespace {
75 class GCOVFunction;
76 
77 class GCOVProfiler {
78 public:
79   GCOVProfiler() : GCOVProfiler(GCOVOptions::getDefault()) {}
80   GCOVProfiler(const GCOVOptions &Opts) : Options(Opts) {
81     assert((Options.EmitNotes || Options.EmitData) &&
82            "GCOVProfiler asked to do nothing?");
83     ReversedVersion[0] = Options.Version[3];
84     ReversedVersion[1] = Options.Version[2];
85     ReversedVersion[2] = Options.Version[1];
86     ReversedVersion[3] = Options.Version[0];
87     ReversedVersion[4] = '\0';
88   }
89   bool runOnModule(Module &M, const TargetLibraryInfo &TLI);
90 
91 private:
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 *getSummaryInfoFunc();
105   Constant *getEndFileFunc();
106 
107   // Create or retrieve an i32 state value that is used to represent the
108   // pred block number for certain non-trivial edges.
109   GlobalVariable *getEdgeStateValue();
110 
111   // Produce a table of pointers to counters, by predecessor and successor
112   // block number.
113   GlobalVariable *buildEdgeLookupTable(Function *F, GlobalVariable *Counter,
114                                        const UniqueVector<BasicBlock *> &Preds,
115                                        const UniqueVector<BasicBlock *> &Succs);
116 
117   // Add the function to write out all our counters to the global destructor
118   // list.
119   Function *
120   insertCounterWriteout(ArrayRef<std::pair<GlobalVariable *, MDNode *>>);
121   Function *insertFlush(ArrayRef<std::pair<GlobalVariable *, MDNode *>>);
122   void insertIndirectCounterIncrement();
123 
124   enum class GCovFileType { GCNO, GCDA };
125   std::string mangleName(const DICompileUnit *CU, GCovFileType FileType);
126 
127   GCOVOptions Options;
128 
129   // Reversed, NUL-terminated copy of Options.Version.
130   char ReversedVersion[5];
131   // Checksum, produced by hash of EdgeDestinations
132   SmallVector<uint32_t, 4> FileChecksums;
133 
134   Module *M;
135   const TargetLibraryInfo *TLI;
136   LLVMContext *Ctx;
137   SmallVector<std::unique_ptr<GCOVFunction>, 16> Funcs;
138 };
139 
140 class GCOVProfilerLegacyPass : public ModulePass {
141 public:
142   static char ID;
143   GCOVProfilerLegacyPass()
144       : GCOVProfilerLegacyPass(GCOVOptions::getDefault()) {}
145   GCOVProfilerLegacyPass(const GCOVOptions &Opts)
146       : ModulePass(ID), Profiler(Opts) {
147     initializeGCOVProfilerLegacyPassPass(*PassRegistry::getPassRegistry());
148   }
149   StringRef getPassName() const override { return "GCOV Profiler"; }
150 
151   bool runOnModule(Module &M) override {
152     auto &TLI = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
153     return Profiler.runOnModule(M, TLI);
154   }
155 
156   void getAnalysisUsage(AnalysisUsage &AU) const override {
157     AU.addRequired<TargetLibraryInfoWrapperPass>();
158   }
159 
160 private:
161   GCOVProfiler Profiler;
162 };
163 }
164 
165 char GCOVProfilerLegacyPass::ID = 0;
166 INITIALIZE_PASS_BEGIN(
167     GCOVProfilerLegacyPass, "insert-gcov-profiling",
168     "Insert instrumentation for GCOV profiling", false, false)
169 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
170 INITIALIZE_PASS_END(
171     GCOVProfilerLegacyPass, "insert-gcov-profiling",
172     "Insert instrumentation for GCOV profiling", false, false)
173 
174 ModulePass *llvm::createGCOVProfilerPass(const GCOVOptions &Options) {
175   return new GCOVProfilerLegacyPass(Options);
176 }
177 
178 static StringRef getFunctionName(const DISubprogram *SP) {
179   if (!SP->getLinkageName().empty())
180     return SP->getLinkageName();
181   return SP->getName();
182 }
183 
184 namespace {
185   class GCOVRecord {
186    protected:
187     static const char *const LinesTag;
188     static const char *const FunctionTag;
189     static const char *const BlockTag;
190     static const char *const EdgeTag;
191 
192     GCOVRecord() = default;
193 
194     void writeBytes(const char *Bytes, int Size) {
195       os->write(Bytes, Size);
196     }
197 
198     void write(uint32_t i) {
199       writeBytes(reinterpret_cast<char*>(&i), 4);
200     }
201 
202     // Returns the length measured in 4-byte blocks that will be used to
203     // represent this string in a GCOV file
204     static unsigned lengthOfGCOVString(StringRef s) {
205       // A GCOV string is a length, followed by a NUL, then between 0 and 3 NULs
206       // padding out to the next 4-byte word. The length is measured in 4-byte
207       // words including padding, not bytes of actual string.
208       return (s.size() / 4) + 1;
209     }
210 
211     void writeGCOVString(StringRef s) {
212       uint32_t Len = lengthOfGCOVString(s);
213       write(Len);
214       writeBytes(s.data(), s.size());
215 
216       // Write 1 to 4 bytes of NUL padding.
217       assert((unsigned)(4 - (s.size() % 4)) > 0);
218       assert((unsigned)(4 - (s.size() % 4)) <= 4);
219       writeBytes("\0\0\0\0", 4 - (s.size() % 4));
220     }
221 
222     raw_ostream *os;
223   };
224   const char *const GCOVRecord::LinesTag = "\0\0\x45\x01";
225   const char *const GCOVRecord::FunctionTag = "\0\0\0\1";
226   const char *const GCOVRecord::BlockTag = "\0\0\x41\x01";
227   const char *const GCOVRecord::EdgeTag = "\0\0\x43\x01";
228 
229   class GCOVFunction;
230   class GCOVBlock;
231 
232   // Constructed only by requesting it from a GCOVBlock, this object stores a
233   // list of line numbers and a single filename, representing lines that belong
234   // to the block.
235   class GCOVLines : public GCOVRecord {
236    public:
237     void addLine(uint32_t Line) {
238       assert(Line != 0 && "Line zero is not a valid real line number.");
239       Lines.push_back(Line);
240     }
241 
242     uint32_t length() const {
243       // Here 2 = 1 for string length + 1 for '0' id#.
244       return lengthOfGCOVString(Filename) + 2 + Lines.size();
245     }
246 
247     void writeOut() {
248       write(0);
249       writeGCOVString(Filename);
250       for (int i = 0, e = Lines.size(); i != e; ++i)
251         write(Lines[i]);
252     }
253 
254     GCOVLines(StringRef F, raw_ostream *os)
255       : Filename(F) {
256       this->os = os;
257     }
258 
259    private:
260     StringRef Filename;
261     SmallVector<uint32_t, 32> Lines;
262   };
263 
264 
265   // Represent a basic block in GCOV. Each block has a unique number in the
266   // function, number of lines belonging to each block, and a set of edges to
267   // other blocks.
268   class GCOVBlock : public GCOVRecord {
269    public:
270     GCOVLines &getFile(StringRef Filename) {
271       return LinesByFile.try_emplace(Filename, Filename, os).first->second;
272     }
273 
274     void addEdge(GCOVBlock &Successor) {
275       OutEdges.push_back(&Successor);
276     }
277 
278     void writeOut() {
279       uint32_t Len = 3;
280       SmallVector<StringMapEntry<GCOVLines> *, 32> SortedLinesByFile;
281       for (auto &I : LinesByFile) {
282         Len += I.second.length();
283         SortedLinesByFile.push_back(&I);
284       }
285 
286       writeBytes(LinesTag, 4);
287       write(Len);
288       write(Number);
289 
290       llvm::sort(
291           SortedLinesByFile.begin(), SortedLinesByFile.end(),
292           [](StringMapEntry<GCOVLines> *LHS, StringMapEntry<GCOVLines> *RHS) {
293             return LHS->getKey() < RHS->getKey();
294           });
295       for (auto &I : SortedLinesByFile)
296         I->getValue().writeOut();
297       write(0);
298       write(0);
299     }
300 
301     GCOVBlock(const GCOVBlock &RHS) : GCOVRecord(RHS), Number(RHS.Number) {
302       // Only allow copy before edges and lines have been added. After that,
303       // there are inter-block pointers (eg: edges) that won't take kindly to
304       // blocks being copied or moved around.
305       assert(LinesByFile.empty());
306       assert(OutEdges.empty());
307     }
308 
309    private:
310     friend class GCOVFunction;
311 
312     GCOVBlock(uint32_t Number, raw_ostream *os)
313         : Number(Number) {
314       this->os = os;
315     }
316 
317     uint32_t Number;
318     StringMap<GCOVLines> LinesByFile;
319     SmallVector<GCOVBlock *, 4> OutEdges;
320   };
321 
322   // A function has a unique identifier, a checksum (we leave as zero) and a
323   // set of blocks and a map of edges between blocks. This is the only GCOV
324   // object users can construct, the blocks and lines will be rooted here.
325   class GCOVFunction : public GCOVRecord {
326    public:
327      GCOVFunction(const DISubprogram *SP, Function *F, raw_ostream *os,
328                   uint32_t Ident, bool UseCfgChecksum, bool ExitBlockBeforeBody)
329          : SP(SP), Ident(Ident), UseCfgChecksum(UseCfgChecksum), CfgChecksum(0),
330            ReturnBlock(1, os) {
331       this->os = os;
332 
333       LLVM_DEBUG(dbgs() << "Function: " << getFunctionName(SP) << "\n");
334 
335       uint32_t i = 0;
336       for (auto &BB : *F) {
337         // Skip index 1 if it's assigned to the ReturnBlock.
338         if (i == 1 && ExitBlockBeforeBody)
339           ++i;
340         Blocks.insert(std::make_pair(&BB, GCOVBlock(i++, os)));
341       }
342       if (!ExitBlockBeforeBody)
343         ReturnBlock.Number = i;
344 
345       std::string FunctionNameAndLine;
346       raw_string_ostream FNLOS(FunctionNameAndLine);
347       FNLOS << getFunctionName(SP) << SP->getLine();
348       FNLOS.flush();
349       FuncChecksum = hash_value(FunctionNameAndLine);
350     }
351 
352     GCOVBlock &getBlock(BasicBlock *BB) {
353       return Blocks.find(BB)->second;
354     }
355 
356     GCOVBlock &getReturnBlock() {
357       return ReturnBlock;
358     }
359 
360     std::string getEdgeDestinations() {
361       std::string EdgeDestinations;
362       raw_string_ostream EDOS(EdgeDestinations);
363       Function *F = Blocks.begin()->first->getParent();
364       for (BasicBlock &I : *F) {
365         GCOVBlock &Block = getBlock(&I);
366         for (int i = 0, e = Block.OutEdges.size(); i != e; ++i)
367           EDOS << Block.OutEdges[i]->Number;
368       }
369       return EdgeDestinations;
370     }
371 
372     uint32_t getFuncChecksum() {
373       return FuncChecksum;
374     }
375 
376     void setCfgChecksum(uint32_t Checksum) {
377       CfgChecksum = Checksum;
378     }
379 
380     void writeOut() {
381       writeBytes(FunctionTag, 4);
382       uint32_t BlockLen = 1 + 1 + 1 + lengthOfGCOVString(getFunctionName(SP)) +
383                           1 + lengthOfGCOVString(SP->getFilename()) + 1;
384       if (UseCfgChecksum)
385         ++BlockLen;
386       write(BlockLen);
387       write(Ident);
388       write(FuncChecksum);
389       if (UseCfgChecksum)
390         write(CfgChecksum);
391       writeGCOVString(getFunctionName(SP));
392       writeGCOVString(SP->getFilename());
393       write(SP->getLine());
394 
395       // Emit count of blocks.
396       writeBytes(BlockTag, 4);
397       write(Blocks.size() + 1);
398       for (int i = 0, e = Blocks.size() + 1; i != e; ++i) {
399         write(0);  // No flags on our blocks.
400       }
401       LLVM_DEBUG(dbgs() << Blocks.size() << " blocks.\n");
402 
403       // Emit edges between blocks.
404       if (Blocks.empty()) return;
405       Function *F = Blocks.begin()->first->getParent();
406       for (BasicBlock &I : *F) {
407         GCOVBlock &Block = getBlock(&I);
408         if (Block.OutEdges.empty()) continue;
409 
410         writeBytes(EdgeTag, 4);
411         write(Block.OutEdges.size() * 2 + 1);
412         write(Block.Number);
413         for (int i = 0, e = Block.OutEdges.size(); i != e; ++i) {
414           LLVM_DEBUG(dbgs() << Block.Number << " -> "
415                             << Block.OutEdges[i]->Number << "\n");
416           write(Block.OutEdges[i]->Number);
417           write(0);  // no flags
418         }
419       }
420 
421       // Emit lines for each block.
422       for (BasicBlock &I : *F)
423         getBlock(&I).writeOut();
424     }
425 
426    private:
427      const DISubprogram *SP;
428     uint32_t Ident;
429     uint32_t FuncChecksum;
430     bool UseCfgChecksum;
431     uint32_t CfgChecksum;
432     DenseMap<BasicBlock *, GCOVBlock> Blocks;
433     GCOVBlock ReturnBlock;
434   };
435 }
436 
437 std::string GCOVProfiler::mangleName(const DICompileUnit *CU,
438                                      GCovFileType OutputType) {
439   bool Notes = OutputType == GCovFileType::GCNO;
440 
441   if (NamedMDNode *GCov = M->getNamedMetadata("llvm.gcov")) {
442     for (int i = 0, e = GCov->getNumOperands(); i != e; ++i) {
443       MDNode *N = GCov->getOperand(i);
444       bool ThreeElement = N->getNumOperands() == 3;
445       if (!ThreeElement && N->getNumOperands() != 2)
446         continue;
447       if (dyn_cast<MDNode>(N->getOperand(ThreeElement ? 2 : 1)) != CU)
448         continue;
449 
450       if (ThreeElement) {
451         // These nodes have no mangling to apply, it's stored mangled in the
452         // bitcode.
453         MDString *NotesFile = dyn_cast<MDString>(N->getOperand(0));
454         MDString *DataFile = dyn_cast<MDString>(N->getOperand(1));
455         if (!NotesFile || !DataFile)
456           continue;
457         return Notes ? NotesFile->getString() : DataFile->getString();
458       }
459 
460       MDString *GCovFile = dyn_cast<MDString>(N->getOperand(0));
461       if (!GCovFile)
462         continue;
463 
464       SmallString<128> Filename = GCovFile->getString();
465       sys::path::replace_extension(Filename, Notes ? "gcno" : "gcda");
466       return Filename.str();
467     }
468   }
469 
470   SmallString<128> Filename = CU->getFilename();
471   sys::path::replace_extension(Filename, Notes ? "gcno" : "gcda");
472   StringRef FName = sys::path::filename(Filename);
473   SmallString<128> CurPath;
474   if (sys::fs::current_path(CurPath)) return FName;
475   sys::path::append(CurPath, FName);
476   return CurPath.str();
477 }
478 
479 bool GCOVProfiler::runOnModule(Module &M, const TargetLibraryInfo &TLI) {
480   this->M = &M;
481   this->TLI = &TLI;
482   Ctx = &M.getContext();
483 
484   if (Options.EmitNotes) emitProfileNotes();
485   if (Options.EmitData) return emitProfileArcs();
486   return false;
487 }
488 
489 PreservedAnalyses GCOVProfilerPass::run(Module &M,
490                                         ModuleAnalysisManager &AM) {
491 
492   GCOVProfiler Profiler(GCOVOpts);
493 
494   auto &TLI = AM.getResult<TargetLibraryAnalysis>(M);
495   if (!Profiler.runOnModule(M, TLI))
496     return PreservedAnalyses::all();
497 
498   return PreservedAnalyses::none();
499 }
500 
501 static bool functionHasLines(Function &F) {
502   // Check whether this function actually has any source lines. Not only
503   // do these waste space, they also can crash gcov.
504   for (auto &BB : F) {
505     for (auto &I : BB) {
506       // Debug intrinsic locations correspond to the location of the
507       // declaration, not necessarily any statements or expressions.
508       if (isa<DbgInfoIntrinsic>(&I)) continue;
509 
510       const DebugLoc &Loc = I.getDebugLoc();
511       if (!Loc)
512         continue;
513 
514       // Artificial lines such as calls to the global constructors.
515       if (Loc.getLine() == 0) continue;
516 
517       return true;
518     }
519   }
520   return false;
521 }
522 
523 static bool isUsingScopeBasedEH(Function &F) {
524   if (!F.hasPersonalityFn()) return false;
525 
526   EHPersonality Personality = classifyEHPersonality(F.getPersonalityFn());
527   return isScopedEHPersonality(Personality);
528 }
529 
530 static bool shouldKeepInEntry(BasicBlock::iterator It) {
531 	if (isa<AllocaInst>(*It)) return true;
532 	if (isa<DbgInfoIntrinsic>(*It)) return true;
533 	if (auto *II = dyn_cast<IntrinsicInst>(It)) {
534 		if (II->getIntrinsicID() == llvm::Intrinsic::localescape) return true;
535 	}
536 
537 	return false;
538 }
539 
540 void GCOVProfiler::emitProfileNotes() {
541   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
542   if (!CU_Nodes) return;
543 
544   for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
545     // Each compile unit gets its own .gcno file. This means that whether we run
546     // this pass over the original .o's as they're produced, or run it after
547     // LTO, we'll generate the same .gcno files.
548 
549     auto *CU = cast<DICompileUnit>(CU_Nodes->getOperand(i));
550 
551     // Skip module skeleton (and module) CUs.
552     if (CU->getDWOId())
553       continue;
554 
555     std::error_code EC;
556     raw_fd_ostream out(mangleName(CU, GCovFileType::GCNO), EC, sys::fs::F_None);
557     if (EC) {
558       Ctx->emitError(Twine("failed to open coverage notes file for writing: ") +
559                      EC.message());
560       continue;
561     }
562 
563     std::string EdgeDestinations;
564 
565     unsigned FunctionIdent = 0;
566     for (auto &F : M->functions()) {
567       DISubprogram *SP = F.getSubprogram();
568       if (!SP) continue;
569       if (!functionHasLines(F)) continue;
570       // TODO: Functions using scope-based EH are currently not supported.
571       if (isUsingScopeBasedEH(F)) continue;
572 
573       // gcov expects every function to start with an entry block that has a
574       // single successor, so split the entry block to make sure of that.
575       BasicBlock &EntryBlock = F.getEntryBlock();
576       BasicBlock::iterator It = EntryBlock.begin();
577       while (shouldKeepInEntry(It))
578         ++It;
579       EntryBlock.splitBasicBlock(It);
580 
581       Funcs.push_back(make_unique<GCOVFunction>(SP, &F, &out, FunctionIdent++,
582                                                 Options.UseCfgChecksum,
583                                                 Options.ExitBlockBeforeBody));
584       GCOVFunction &Func = *Funcs.back();
585 
586       for (auto &BB : F) {
587         GCOVBlock &Block = Func.getBlock(&BB);
588         TerminatorInst *TI = BB.getTerminator();
589         if (int successors = TI->getNumSuccessors()) {
590           for (int i = 0; i != successors; ++i) {
591             Block.addEdge(Func.getBlock(TI->getSuccessor(i)));
592           }
593         } else if (isa<ReturnInst>(TI)) {
594           Block.addEdge(Func.getReturnBlock());
595         }
596 
597         uint32_t Line = 0;
598         for (auto &I : BB) {
599           // Debug intrinsic locations correspond to the location of the
600           // declaration, not necessarily any statements or expressions.
601           if (isa<DbgInfoIntrinsic>(&I)) continue;
602 
603           const DebugLoc &Loc = I.getDebugLoc();
604           if (!Loc)
605             continue;
606 
607           // Artificial lines such as calls to the global constructors.
608           if (Loc.getLine() == 0) continue;
609 
610           if (Line == Loc.getLine()) continue;
611           Line = Loc.getLine();
612           if (SP != getDISubprogram(Loc.getScope()))
613             continue;
614 
615           GCOVLines &Lines = Block.getFile(SP->getFilename());
616           Lines.addLine(Loc.getLine());
617         }
618       }
619       EdgeDestinations += Func.getEdgeDestinations();
620     }
621 
622     FileChecksums.push_back(hash_value(EdgeDestinations));
623     out.write("oncg", 4);
624     out.write(ReversedVersion, 4);
625     out.write(reinterpret_cast<char*>(&FileChecksums.back()), 4);
626 
627     for (auto &Func : Funcs) {
628       Func->setCfgChecksum(FileChecksums.back());
629       Func->writeOut();
630     }
631 
632     out.write("\0\0\0\0\0\0\0\0", 8);  // EOF
633     out.close();
634   }
635 }
636 
637 bool GCOVProfiler::emitProfileArcs() {
638   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
639   if (!CU_Nodes) return false;
640 
641   bool Result = false;
642   bool InsertIndCounterIncrCode = false;
643   for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
644     SmallVector<std::pair<GlobalVariable *, MDNode *>, 8> CountersBySP;
645     for (auto &F : M->functions()) {
646       DISubprogram *SP = F.getSubprogram();
647       if (!SP) continue;
648       if (!functionHasLines(F)) continue;
649       // TODO: Functions using scope-based EH are currently not supported.
650       if (isUsingScopeBasedEH(F)) continue;
651       if (!Result) Result = true;
652 
653       unsigned Edges = 0;
654       for (auto &BB : F) {
655         TerminatorInst *TI = BB.getTerminator();
656         if (isa<ReturnInst>(TI))
657           ++Edges;
658         else
659           Edges += TI->getNumSuccessors();
660       }
661 
662       ArrayType *CounterTy =
663         ArrayType::get(Type::getInt64Ty(*Ctx), Edges);
664       GlobalVariable *Counters =
665         new GlobalVariable(*M, CounterTy, false,
666                            GlobalValue::InternalLinkage,
667                            Constant::getNullValue(CounterTy),
668                            "__llvm_gcov_ctr");
669       CountersBySP.push_back(std::make_pair(Counters, SP));
670 
671       UniqueVector<BasicBlock *> ComplexEdgePreds;
672       UniqueVector<BasicBlock *> ComplexEdgeSuccs;
673 
674       unsigned Edge = 0;
675       for (auto &BB : F) {
676         TerminatorInst *TI = BB.getTerminator();
677         int Successors = isa<ReturnInst>(TI) ? 1 : TI->getNumSuccessors();
678         if (Successors) {
679           if (Successors == 1) {
680             IRBuilder<> Builder(&*BB.getFirstInsertionPt());
681             Value *Counter = Builder.CreateConstInBoundsGEP2_64(Counters, 0,
682                                                                 Edge);
683             Value *Count = Builder.CreateLoad(Counter);
684             Count = Builder.CreateAdd(Count, Builder.getInt64(1));
685             Builder.CreateStore(Count, Counter);
686           } else if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
687             IRBuilder<> Builder(BI);
688             Value *Sel = Builder.CreateSelect(BI->getCondition(),
689                                               Builder.getInt64(Edge),
690                                               Builder.getInt64(Edge + 1));
691             Value *Counter = Builder.CreateInBoundsGEP(
692                 Counters->getValueType(), Counters, {Builder.getInt64(0), Sel});
693             Value *Count = Builder.CreateLoad(Counter);
694             Count = Builder.CreateAdd(Count, Builder.getInt64(1));
695             Builder.CreateStore(Count, Counter);
696           } else {
697             ComplexEdgePreds.insert(&BB);
698             for (int i = 0; i != Successors; ++i)
699               ComplexEdgeSuccs.insert(TI->getSuccessor(i));
700           }
701 
702           Edge += Successors;
703         }
704       }
705 
706       if (!ComplexEdgePreds.empty()) {
707         GlobalVariable *EdgeTable =
708           buildEdgeLookupTable(&F, Counters,
709                                ComplexEdgePreds, ComplexEdgeSuccs);
710         GlobalVariable *EdgeState = getEdgeStateValue();
711 
712         for (int i = 0, e = ComplexEdgePreds.size(); i != e; ++i) {
713           IRBuilder<> Builder(&*ComplexEdgePreds[i + 1]->getFirstInsertionPt());
714           Builder.CreateStore(Builder.getInt32(i), EdgeState);
715         }
716 
717         for (int i = 0, e = ComplexEdgeSuccs.size(); i != e; ++i) {
718           // Call runtime to perform increment.
719           IRBuilder<> Builder(&*ComplexEdgeSuccs[i + 1]->getFirstInsertionPt());
720           Value *CounterPtrArray =
721             Builder.CreateConstInBoundsGEP2_64(EdgeTable, 0,
722                                                i * ComplexEdgePreds.size());
723 
724           // Build code to increment the counter.
725           InsertIndCounterIncrCode = true;
726           Builder.CreateCall(getIncrementIndirectCounterFunc(),
727                              {EdgeState, CounterPtrArray});
728         }
729       }
730     }
731 
732     Function *WriteoutF = insertCounterWriteout(CountersBySP);
733     Function *FlushF = insertFlush(CountersBySP);
734 
735     // Create a small bit of code that registers the "__llvm_gcov_writeout" to
736     // be executed at exit and the "__llvm_gcov_flush" function to be executed
737     // when "__gcov_flush" is called.
738     FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
739     Function *F = Function::Create(FTy, GlobalValue::InternalLinkage,
740                                    "__llvm_gcov_init", M);
741     F->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
742     F->setLinkage(GlobalValue::InternalLinkage);
743     F->addFnAttr(Attribute::NoInline);
744     if (Options.NoRedZone)
745       F->addFnAttr(Attribute::NoRedZone);
746 
747     BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", F);
748     IRBuilder<> Builder(BB);
749 
750     FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
751     Type *Params[] = {
752       PointerType::get(FTy, 0),
753       PointerType::get(FTy, 0)
754     };
755     FTy = FunctionType::get(Builder.getVoidTy(), Params, false);
756 
757     // Initialize the environment and register the local writeout and flush
758     // functions.
759     Constant *GCOVInit = M->getOrInsertFunction("llvm_gcov_init", FTy);
760     Builder.CreateCall(GCOVInit, {WriteoutF, FlushF});
761     Builder.CreateRetVoid();
762 
763     appendToGlobalCtors(*M, F, 0);
764   }
765 
766   if (InsertIndCounterIncrCode)
767     insertIndirectCounterIncrement();
768 
769   return Result;
770 }
771 
772 // All edges with successors that aren't branches are "complex", because it
773 // requires complex logic to pick which counter to update.
774 GlobalVariable *GCOVProfiler::buildEdgeLookupTable(
775     Function *F,
776     GlobalVariable *Counters,
777     const UniqueVector<BasicBlock *> &Preds,
778     const UniqueVector<BasicBlock *> &Succs) {
779   // TODO: support invoke, threads. We rely on the fact that nothing can modify
780   // the whole-Module pred edge# between the time we set it and the time we next
781   // read it. Threads and invoke make this untrue.
782 
783   // emit [(succs * preds) x i64*], logically [succ x [pred x i64*]].
784   size_t TableSize = Succs.size() * Preds.size();
785   Type *Int64PtrTy = Type::getInt64PtrTy(*Ctx);
786   ArrayType *EdgeTableTy = ArrayType::get(Int64PtrTy, TableSize);
787 
788   std::unique_ptr<Constant * []> EdgeTable(new Constant *[TableSize]);
789   Constant *NullValue = Constant::getNullValue(Int64PtrTy);
790   for (size_t i = 0; i != TableSize; ++i)
791     EdgeTable[i] = NullValue;
792 
793   unsigned Edge = 0;
794   for (BasicBlock &BB : *F) {
795     TerminatorInst *TI = BB.getTerminator();
796     int Successors = isa<ReturnInst>(TI) ? 1 : TI->getNumSuccessors();
797     if (Successors > 1 && !isa<BranchInst>(TI) && !isa<ReturnInst>(TI)) {
798       for (int i = 0; i != Successors; ++i) {
799         BasicBlock *Succ = TI->getSuccessor(i);
800         IRBuilder<> Builder(Succ);
801         Value *Counter = Builder.CreateConstInBoundsGEP2_64(Counters, 0,
802                                                             Edge + i);
803         EdgeTable[((Succs.idFor(Succ) - 1) * Preds.size()) +
804                   (Preds.idFor(&BB) - 1)] = cast<Constant>(Counter);
805       }
806     }
807     Edge += Successors;
808   }
809 
810   GlobalVariable *EdgeTableGV =
811       new GlobalVariable(
812           *M, EdgeTableTy, true, GlobalValue::InternalLinkage,
813           ConstantArray::get(EdgeTableTy,
814                              makeArrayRef(&EdgeTable[0],TableSize)),
815           "__llvm_gcda_edge_table");
816   EdgeTableGV->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
817   return EdgeTableGV;
818 }
819 
820 Constant *GCOVProfiler::getStartFileFunc() {
821   Type *Args[] = {
822     Type::getInt8PtrTy(*Ctx),  // const char *orig_filename
823     Type::getInt8PtrTy(*Ctx),  // const char version[4]
824     Type::getInt32Ty(*Ctx),    // uint32_t checksum
825   };
826   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
827   auto *Res = M->getOrInsertFunction("llvm_gcda_start_file", FTy);
828   if (Function *FunRes = dyn_cast<Function>(Res))
829     if (auto AK = TLI->getExtAttrForI32Param(false))
830       FunRes->addParamAttr(2, AK);
831   return Res;
832 
833 }
834 
835 Constant *GCOVProfiler::getIncrementIndirectCounterFunc() {
836   Type *Int32Ty = Type::getInt32Ty(*Ctx);
837   Type *Int64Ty = Type::getInt64Ty(*Ctx);
838   Type *Args[] = {
839     Int32Ty->getPointerTo(),                // uint32_t *predecessor
840     Int64Ty->getPointerTo()->getPointerTo() // uint64_t **counters
841   };
842   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
843   return M->getOrInsertFunction("__llvm_gcov_indirect_counter_increment", FTy);
844 }
845 
846 Constant *GCOVProfiler::getEmitFunctionFunc() {
847   Type *Args[] = {
848     Type::getInt32Ty(*Ctx),    // uint32_t ident
849     Type::getInt8PtrTy(*Ctx),  // const char *function_name
850     Type::getInt32Ty(*Ctx),    // uint32_t func_checksum
851     Type::getInt8Ty(*Ctx),     // uint8_t use_extra_checksum
852     Type::getInt32Ty(*Ctx),    // uint32_t cfg_checksum
853   };
854   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
855   auto *Res = M->getOrInsertFunction("llvm_gcda_emit_function", FTy);
856   if (Function *FunRes = dyn_cast<Function>(Res))
857     if (auto AK = TLI->getExtAttrForI32Param(false)) {
858       FunRes->addParamAttr(0, AK);
859       FunRes->addParamAttr(2, AK);
860       FunRes->addParamAttr(3, AK);
861       FunRes->addParamAttr(4, AK);
862     }
863   return Res;
864 }
865 
866 Constant *GCOVProfiler::getEmitArcsFunc() {
867   Type *Args[] = {
868     Type::getInt32Ty(*Ctx),     // uint32_t num_counters
869     Type::getInt64PtrTy(*Ctx),  // uint64_t *counters
870   };
871   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), Args, false);
872   auto *Res = M->getOrInsertFunction("llvm_gcda_emit_arcs", FTy);
873   if (Function *FunRes = dyn_cast<Function>(Res))
874     if (auto AK = TLI->getExtAttrForI32Param(false))
875       FunRes->addParamAttr(0, AK);
876   return Res;
877 }
878 
879 Constant *GCOVProfiler::getSummaryInfoFunc() {
880   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
881   return M->getOrInsertFunction("llvm_gcda_summary_info", FTy);
882 }
883 
884 Constant *GCOVProfiler::getEndFileFunc() {
885   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
886   return M->getOrInsertFunction("llvm_gcda_end_file", FTy);
887 }
888 
889 GlobalVariable *GCOVProfiler::getEdgeStateValue() {
890   GlobalVariable *GV = M->getGlobalVariable("__llvm_gcov_global_state_pred");
891   if (!GV) {
892     GV = new GlobalVariable(*M, Type::getInt32Ty(*Ctx), false,
893                             GlobalValue::InternalLinkage,
894                             ConstantInt::get(Type::getInt32Ty(*Ctx),
895                                              0xffffffff),
896                             "__llvm_gcov_global_state_pred");
897     GV->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
898   }
899   return GV;
900 }
901 
902 Function *GCOVProfiler::insertCounterWriteout(
903     ArrayRef<std::pair<GlobalVariable *, MDNode *> > CountersBySP) {
904   FunctionType *WriteoutFTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
905   Function *WriteoutF = M->getFunction("__llvm_gcov_writeout");
906   if (!WriteoutF)
907     WriteoutF = Function::Create(WriteoutFTy, GlobalValue::InternalLinkage,
908                                  "__llvm_gcov_writeout", M);
909   WriteoutF->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
910   WriteoutF->addFnAttr(Attribute::NoInline);
911   if (Options.NoRedZone)
912     WriteoutF->addFnAttr(Attribute::NoRedZone);
913 
914   BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", WriteoutF);
915   IRBuilder<> Builder(BB);
916 
917   Constant *StartFile = getStartFileFunc();
918   Constant *EmitFunction = getEmitFunctionFunc();
919   Constant *EmitArcs = getEmitArcsFunc();
920   Constant *SummaryInfo = getSummaryInfoFunc();
921   Constant *EndFile = getEndFileFunc();
922 
923   NamedMDNode *CUNodes = M->getNamedMetadata("llvm.dbg.cu");
924   if (!CUNodes) {
925     Builder.CreateRetVoid();
926     return WriteoutF;
927   }
928 
929   // Collect the relevant data into a large constant data structure that we can
930   // walk to write out everything.
931   StructType *StartFileCallArgsTy = StructType::create(
932       {Builder.getInt8PtrTy(), Builder.getInt8PtrTy(), Builder.getInt32Ty()});
933   StructType *EmitFunctionCallArgsTy = StructType::create(
934       {Builder.getInt32Ty(), Builder.getInt8PtrTy(), Builder.getInt32Ty(),
935        Builder.getInt8Ty(), Builder.getInt32Ty()});
936   StructType *EmitArcsCallArgsTy = StructType::create(
937       {Builder.getInt32Ty(), Builder.getInt64Ty()->getPointerTo()});
938   StructType *FileInfoTy =
939       StructType::create({StartFileCallArgsTy, Builder.getInt32Ty(),
940                           EmitFunctionCallArgsTy->getPointerTo(),
941                           EmitArcsCallArgsTy->getPointerTo()});
942 
943   Constant *Zero32 = Builder.getInt32(0);
944   // Build an explicit array of two zeros for use in ConstantExpr GEP building.
945   Constant *TwoZero32s[] = {Zero32, Zero32};
946 
947   SmallVector<Constant *, 8> FileInfos;
948   for (int i : llvm::seq<int>(0, CUNodes->getNumOperands())) {
949     auto *CU = cast<DICompileUnit>(CUNodes->getOperand(i));
950 
951     // Skip module skeleton (and module) CUs.
952     if (CU->getDWOId())
953       continue;
954 
955     std::string FilenameGcda = mangleName(CU, GCovFileType::GCDA);
956     uint32_t CfgChecksum = FileChecksums.empty() ? 0 : FileChecksums[i];
957     auto *StartFileCallArgs = ConstantStruct::get(
958         StartFileCallArgsTy, {Builder.CreateGlobalStringPtr(FilenameGcda),
959                               Builder.CreateGlobalStringPtr(ReversedVersion),
960                               Builder.getInt32(CfgChecksum)});
961 
962     SmallVector<Constant *, 8> EmitFunctionCallArgsArray;
963     SmallVector<Constant *, 8> EmitArcsCallArgsArray;
964     for (int j : llvm::seq<int>(0, CountersBySP.size())) {
965       auto *SP = cast_or_null<DISubprogram>(CountersBySP[j].second);
966       uint32_t FuncChecksum = Funcs.empty() ? 0 : Funcs[j]->getFuncChecksum();
967       EmitFunctionCallArgsArray.push_back(ConstantStruct::get(
968           EmitFunctionCallArgsTy,
969           {Builder.getInt32(j),
970            Options.FunctionNamesInData
971                ? Builder.CreateGlobalStringPtr(getFunctionName(SP))
972                : Constant::getNullValue(Builder.getInt8PtrTy()),
973            Builder.getInt32(FuncChecksum),
974            Builder.getInt8(Options.UseCfgChecksum),
975            Builder.getInt32(CfgChecksum)}));
976 
977       GlobalVariable *GV = CountersBySP[j].first;
978       unsigned Arcs = cast<ArrayType>(GV->getValueType())->getNumElements();
979       EmitArcsCallArgsArray.push_back(ConstantStruct::get(
980           EmitArcsCallArgsTy,
981           {Builder.getInt32(Arcs), ConstantExpr::getInBoundsGetElementPtr(
982                                        GV->getValueType(), GV, TwoZero32s)}));
983     }
984     // Create global arrays for the two emit calls.
985     int CountersSize = CountersBySP.size();
986     assert(CountersSize == (int)EmitFunctionCallArgsArray.size() &&
987            "Mismatched array size!");
988     assert(CountersSize == (int)EmitArcsCallArgsArray.size() &&
989            "Mismatched array size!");
990     auto *EmitFunctionCallArgsArrayTy =
991         ArrayType::get(EmitFunctionCallArgsTy, CountersSize);
992     auto *EmitFunctionCallArgsArrayGV = new GlobalVariable(
993         *M, EmitFunctionCallArgsArrayTy, /*isConstant*/ true,
994         GlobalValue::InternalLinkage,
995         ConstantArray::get(EmitFunctionCallArgsArrayTy,
996                            EmitFunctionCallArgsArray),
997         Twine("__llvm_internal_gcov_emit_function_args.") + Twine(i));
998     auto *EmitArcsCallArgsArrayTy =
999         ArrayType::get(EmitArcsCallArgsTy, CountersSize);
1000     EmitFunctionCallArgsArrayGV->setUnnamedAddr(
1001         GlobalValue::UnnamedAddr::Global);
1002     auto *EmitArcsCallArgsArrayGV = new GlobalVariable(
1003         *M, EmitArcsCallArgsArrayTy, /*isConstant*/ true,
1004         GlobalValue::InternalLinkage,
1005         ConstantArray::get(EmitArcsCallArgsArrayTy, EmitArcsCallArgsArray),
1006         Twine("__llvm_internal_gcov_emit_arcs_args.") + Twine(i));
1007     EmitArcsCallArgsArrayGV->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
1008 
1009     FileInfos.push_back(ConstantStruct::get(
1010         FileInfoTy,
1011         {StartFileCallArgs, Builder.getInt32(CountersSize),
1012          ConstantExpr::getInBoundsGetElementPtr(EmitFunctionCallArgsArrayTy,
1013                                                 EmitFunctionCallArgsArrayGV,
1014                                                 TwoZero32s),
1015          ConstantExpr::getInBoundsGetElementPtr(
1016              EmitArcsCallArgsArrayTy, EmitArcsCallArgsArrayGV, TwoZero32s)}));
1017   }
1018 
1019   // If we didn't find anything to actually emit, bail on out.
1020   if (FileInfos.empty()) {
1021     Builder.CreateRetVoid();
1022     return WriteoutF;
1023   }
1024 
1025   // To simplify code, we cap the number of file infos we write out to fit
1026   // easily in a 32-bit signed integer. This gives consistent behavior between
1027   // 32-bit and 64-bit systems without requiring (potentially very slow) 64-bit
1028   // operations on 32-bit systems. It also seems unreasonable to try to handle
1029   // more than 2 billion files.
1030   if ((int64_t)FileInfos.size() > (int64_t)INT_MAX)
1031     FileInfos.resize(INT_MAX);
1032 
1033   // Create a global for the entire data structure so we can walk it more
1034   // easily.
1035   auto *FileInfoArrayTy = ArrayType::get(FileInfoTy, FileInfos.size());
1036   auto *FileInfoArrayGV = new GlobalVariable(
1037       *M, FileInfoArrayTy, /*isConstant*/ true, GlobalValue::InternalLinkage,
1038       ConstantArray::get(FileInfoArrayTy, FileInfos),
1039       "__llvm_internal_gcov_emit_file_info");
1040   FileInfoArrayGV->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
1041 
1042   // Create the CFG for walking this data structure.
1043   auto *FileLoopHeader =
1044       BasicBlock::Create(*Ctx, "file.loop.header", WriteoutF);
1045   auto *CounterLoopHeader =
1046       BasicBlock::Create(*Ctx, "counter.loop.header", WriteoutF);
1047   auto *FileLoopLatch = BasicBlock::Create(*Ctx, "file.loop.latch", WriteoutF);
1048   auto *ExitBB = BasicBlock::Create(*Ctx, "exit", WriteoutF);
1049 
1050   // We always have at least one file, so just branch to the header.
1051   Builder.CreateBr(FileLoopHeader);
1052 
1053   // The index into the files structure is our loop induction variable.
1054   Builder.SetInsertPoint(FileLoopHeader);
1055   PHINode *IV =
1056       Builder.CreatePHI(Builder.getInt32Ty(), /*NumReservedValues*/ 2);
1057   IV->addIncoming(Builder.getInt32(0), BB);
1058   auto *FileInfoPtr =
1059       Builder.CreateInBoundsGEP(FileInfoArrayGV, {Builder.getInt32(0), IV});
1060   auto *StartFileCallArgsPtr = Builder.CreateStructGEP(FileInfoPtr, 0);
1061   auto *StartFileCall = Builder.CreateCall(
1062       StartFile,
1063       {Builder.CreateLoad(Builder.CreateStructGEP(StartFileCallArgsPtr, 0)),
1064        Builder.CreateLoad(Builder.CreateStructGEP(StartFileCallArgsPtr, 1)),
1065        Builder.CreateLoad(Builder.CreateStructGEP(StartFileCallArgsPtr, 2))});
1066   if (auto AK = TLI->getExtAttrForI32Param(false))
1067     StartFileCall->addParamAttr(2, AK);
1068   auto *NumCounters =
1069       Builder.CreateLoad(Builder.CreateStructGEP(FileInfoPtr, 1));
1070   auto *EmitFunctionCallArgsArray =
1071       Builder.CreateLoad(Builder.CreateStructGEP(FileInfoPtr, 2));
1072   auto *EmitArcsCallArgsArray =
1073       Builder.CreateLoad(Builder.CreateStructGEP(FileInfoPtr, 3));
1074   auto *EnterCounterLoopCond =
1075       Builder.CreateICmpSLT(Builder.getInt32(0), NumCounters);
1076   Builder.CreateCondBr(EnterCounterLoopCond, CounterLoopHeader, FileLoopLatch);
1077 
1078   Builder.SetInsertPoint(CounterLoopHeader);
1079   auto *JV = Builder.CreatePHI(Builder.getInt32Ty(), /*NumReservedValues*/ 2);
1080   JV->addIncoming(Builder.getInt32(0), FileLoopHeader);
1081   auto *EmitFunctionCallArgsPtr =
1082       Builder.CreateInBoundsGEP(EmitFunctionCallArgsArray, {JV});
1083   auto *EmitFunctionCall = Builder.CreateCall(
1084       EmitFunction,
1085       {Builder.CreateLoad(Builder.CreateStructGEP(EmitFunctionCallArgsPtr, 0)),
1086        Builder.CreateLoad(Builder.CreateStructGEP(EmitFunctionCallArgsPtr, 1)),
1087        Builder.CreateLoad(Builder.CreateStructGEP(EmitFunctionCallArgsPtr, 2)),
1088        Builder.CreateLoad(Builder.CreateStructGEP(EmitFunctionCallArgsPtr, 3)),
1089        Builder.CreateLoad(
1090            Builder.CreateStructGEP(EmitFunctionCallArgsPtr, 4))});
1091   if (auto AK = TLI->getExtAttrForI32Param(false)) {
1092     EmitFunctionCall->addParamAttr(0, AK);
1093     EmitFunctionCall->addParamAttr(2, AK);
1094     EmitFunctionCall->addParamAttr(3, AK);
1095     EmitFunctionCall->addParamAttr(4, AK);
1096   }
1097   auto *EmitArcsCallArgsPtr =
1098       Builder.CreateInBoundsGEP(EmitArcsCallArgsArray, {JV});
1099   auto *EmitArcsCall = Builder.CreateCall(
1100       EmitArcs,
1101       {Builder.CreateLoad(Builder.CreateStructGEP(EmitArcsCallArgsPtr, 0)),
1102        Builder.CreateLoad(Builder.CreateStructGEP(EmitArcsCallArgsPtr, 1))});
1103   if (auto AK = TLI->getExtAttrForI32Param(false))
1104     EmitArcsCall->addParamAttr(0, AK);
1105   auto *NextJV = Builder.CreateAdd(JV, Builder.getInt32(1));
1106   auto *CounterLoopCond = Builder.CreateICmpSLT(NextJV, NumCounters);
1107   Builder.CreateCondBr(CounterLoopCond, CounterLoopHeader, FileLoopLatch);
1108   JV->addIncoming(NextJV, CounterLoopHeader);
1109 
1110   Builder.SetInsertPoint(FileLoopLatch);
1111   Builder.CreateCall(SummaryInfo, {});
1112   Builder.CreateCall(EndFile, {});
1113   auto *NextIV = Builder.CreateAdd(IV, Builder.getInt32(1));
1114   auto *FileLoopCond =
1115       Builder.CreateICmpSLT(NextIV, Builder.getInt32(FileInfos.size()));
1116   Builder.CreateCondBr(FileLoopCond, FileLoopHeader, ExitBB);
1117   IV->addIncoming(NextIV, FileLoopLatch);
1118 
1119   Builder.SetInsertPoint(ExitBB);
1120   Builder.CreateRetVoid();
1121 
1122   return WriteoutF;
1123 }
1124 
1125 void GCOVProfiler::insertIndirectCounterIncrement() {
1126   Function *Fn =
1127     cast<Function>(GCOVProfiler::getIncrementIndirectCounterFunc());
1128   Fn->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
1129   Fn->setLinkage(GlobalValue::InternalLinkage);
1130   Fn->addFnAttr(Attribute::NoInline);
1131   if (Options.NoRedZone)
1132     Fn->addFnAttr(Attribute::NoRedZone);
1133 
1134   // Create basic blocks for function.
1135   BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", Fn);
1136   IRBuilder<> Builder(BB);
1137 
1138   BasicBlock *PredNotNegOne = BasicBlock::Create(*Ctx, "", Fn);
1139   BasicBlock *CounterEnd = BasicBlock::Create(*Ctx, "", Fn);
1140   BasicBlock *Exit = BasicBlock::Create(*Ctx, "exit", Fn);
1141 
1142   // uint32_t pred = *predecessor;
1143   // if (pred == 0xffffffff) return;
1144   Argument *Arg = &*Fn->arg_begin();
1145   Arg->setName("predecessor");
1146   Value *Pred = Builder.CreateLoad(Arg, "pred");
1147   Value *Cond = Builder.CreateICmpEQ(Pred, Builder.getInt32(0xffffffff));
1148   BranchInst::Create(Exit, PredNotNegOne, Cond, BB);
1149 
1150   Builder.SetInsertPoint(PredNotNegOne);
1151 
1152   // uint64_t *counter = counters[pred];
1153   // if (!counter) return;
1154   Value *ZExtPred = Builder.CreateZExt(Pred, Builder.getInt64Ty());
1155   Arg = &*std::next(Fn->arg_begin());
1156   Arg->setName("counters");
1157   Value *GEP = Builder.CreateGEP(Type::getInt64PtrTy(*Ctx), Arg, ZExtPred);
1158   Value *Counter = Builder.CreateLoad(GEP, "counter");
1159   Cond = Builder.CreateICmpEQ(Counter,
1160                               Constant::getNullValue(
1161                                   Builder.getInt64Ty()->getPointerTo()));
1162   Builder.CreateCondBr(Cond, Exit, CounterEnd);
1163 
1164   // ++*counter;
1165   Builder.SetInsertPoint(CounterEnd);
1166   Value *Add = Builder.CreateAdd(Builder.CreateLoad(Counter),
1167                                  Builder.getInt64(1));
1168   Builder.CreateStore(Add, Counter);
1169   Builder.CreateBr(Exit);
1170 
1171   // Fill in the exit block.
1172   Builder.SetInsertPoint(Exit);
1173   Builder.CreateRetVoid();
1174 }
1175 
1176 Function *GCOVProfiler::
1177 insertFlush(ArrayRef<std::pair<GlobalVariable*, MDNode*> > CountersBySP) {
1178   FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
1179   Function *FlushF = M->getFunction("__llvm_gcov_flush");
1180   if (!FlushF)
1181     FlushF = Function::Create(FTy, GlobalValue::InternalLinkage,
1182                               "__llvm_gcov_flush", M);
1183   else
1184     FlushF->setLinkage(GlobalValue::InternalLinkage);
1185   FlushF->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
1186   FlushF->addFnAttr(Attribute::NoInline);
1187   if (Options.NoRedZone)
1188     FlushF->addFnAttr(Attribute::NoRedZone);
1189 
1190   BasicBlock *Entry = BasicBlock::Create(*Ctx, "entry", FlushF);
1191 
1192   // Write out the current counters.
1193   Constant *WriteoutF = M->getFunction("__llvm_gcov_writeout");
1194   assert(WriteoutF && "Need to create the writeout function first!");
1195 
1196   IRBuilder<> Builder(Entry);
1197   Builder.CreateCall(WriteoutF, {});
1198 
1199   // Zero out the counters.
1200   for (const auto &I : CountersBySP) {
1201     GlobalVariable *GV = I.first;
1202     Constant *Null = Constant::getNullValue(GV->getValueType());
1203     Builder.CreateStore(Null, GV);
1204   }
1205 
1206   Type *RetTy = FlushF->getReturnType();
1207   if (RetTy == Type::getVoidTy(*Ctx))
1208     Builder.CreateRetVoid();
1209   else if (RetTy->isIntegerTy())
1210     // Used if __llvm_gcov_flush was implicitly declared.
1211     Builder.CreateRet(ConstantInt::get(RetTy, 0));
1212   else
1213     report_fatal_error("invalid return type for __llvm_gcov_flush");
1214 
1215   return FlushF;
1216 }
1217