Correctly report modified status for GCOVProfiling

[serge-sans-paille]

Summary

Related to https://reviews.llvm.org/D80916

[calixte]

llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp

572

My bad...
Anyway there is some extra flush/dump only if there are some fork/exec*.
So if I understand correctly the purpose of the returned boolean, you need to check if a flush/dump has been added or not and check if emitProfileArcs changed something and return a OR on these two values.

[serge-sans-paille]

Take review into account.

llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp

private:
 
   // Add the function to write out all our counters to the global destructor
   // list.
   Function *
   insertCounterWriteout(ArrayRef<std::pair<GlobalVariable *, MDNode *>>);
   Function *insertReset(ArrayRef<std::pair<GlobalVariable *, MDNode *>>);
   Function *insertFlush(Function *ResetF);
 
-  void AddFlushBeforeForkAndExec();
+  bool AddFlushBeforeForkAndExec();
 
   enum class GCovFileType { GCNO, GCDA };
   std::string mangleName(const DICompileUnit *CU, GCovFileType FileType);
 
   GCOVOptions Options;
 
   // Reversed, NUL-terminated copy of Options.Version.
   char ReversedVersion[5];

 }
 
 bool GCOVProfiler::runOnModule(
     Module &M, std::function<const TargetLibraryInfo &(Function &F)> GetTLI) {
   this->M = &M;
   this->GetTLI = std::move(GetTLI);
   Ctx = &M.getContext();
 
-  AddFlushBeforeForkAndExec();
+  bool Modified = AddFlushBeforeForkAndExec();
 
   FilterRe = createRegexesFromString(Options.Filter);
   ExcludeRe = createRegexesFromString(Options.Exclude);
 
   if (Options.EmitNotes) emitProfileNotes();
-  if (Options.EmitData) return emitProfileArcs();
-  return false;
+  if (Options.EmitData)
+    Modified |= emitProfileArcs();
+  return Modified;
 }
 
 PreservedAnalyses GCOVProfilerPass::run(Module &M,
                                         ModuleAnalysisManager &AM) {
 
   GCOVProfiler Profiler(GCOVOpts);
   FunctionAnalysisManager &FAM =
       AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
static bool shouldKeepInEntry(BasicBlock::iterator It) {
   if (isa<DbgInfoIntrinsic>(*It)) return true;
   if (auto *II = dyn_cast<IntrinsicInst>(It)) {
     if (II->getIntrinsicID() == llvm::Intrinsic::localescape) return true;
   }
 
   return false;
 }
 
-void GCOVProfiler::AddFlushBeforeForkAndExec() {
+bool GCOVProfiler::AddFlushBeforeForkAndExec() {
   SmallVector<CallInst *, 2> Forks;
   SmallVector<CallInst *, 2> Execs;
   for (auto &F : M->functions()) {
     auto *TLI = &GetTLI(F);
     for (auto &I : instructions(F)) {
       if (CallInst *CI = dyn_cast<CallInst>(&I)) {
         if (Function *Callee = CI->getCalledFunction()) {
           LibFunc LF;
for (auto E : Execs) {
     Builder.SetInsertPoint(&*NextInst);
     // If the exec** fails we must reset the counters since they've been
     // dumped
     FunctionCallee ResetF = M->getOrInsertFunction("llvm_reset_counters", FTy);
     Builder.CreateCall(ResetF)->setDebugLoc(Loc);
     Parent->splitBasicBlock(NextInst);
     Parent->back().setDebugLoc(Loc);
   }
+
+  return !Forks.empty() || !Execs.empty();
 }
 
 void GCOVProfiler::emitProfileNotes() {
   NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
   if (!CU_Nodes) return;
 
   for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
     // Each compile unit gets its own .gcno file. This means that whether we run