Correctly track gcov update

[serge-sans-paille]

Summary

Adding a new function automatically leads to changed IR.

[calixte]

llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp

870

probably useless

[calixte]

LGTM

llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp

for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
     for (auto &F : M->functions()) {
       DISubprogram *SP = F.getSubprogram();
       unsigned EndLine;
       if (!SP) continue;
       if (!functionHasLines(F, EndLine) || !isFunctionInstrumented(F))
         continue;
       // TODO: Functions using scope-based EH are currently not supported.
       if (isUsingScopeBasedEH(F)) continue;
-      if (!Result) Result = true;
 
       DenseMap<std::pair<BasicBlock *, BasicBlock *>, unsigned> EdgeToCounter;
       unsigned Edges = 0;
       for (auto &BB : F) {
         Instruction *TI = BB.getTerminator();
         if (isa<ReturnInst>(TI)) {
           EdgeToCounter[{&BB, nullptr}] = Edges++;
         } else {
           for (BasicBlock *Succ : successors(TI)) {
             EdgeToCounter[{&BB, Succ}] = Edges++;
           }
         }
       }
 
       ArrayType *CounterTy =
         ArrayType::get(Type::getInt64Ty(*Ctx), Edges);
       GlobalVariable *Counters =
         new GlobalVariable(*M, CounterTy, false,
                            GlobalValue::InternalLinkage,
                            Constant::getNullValue(CounterTy),
                            "__llvm_gcov_ctr");
       CountersBySP.push_back(std::make_pair(Counters, SP));
 
+      Result = true;
+
       // If a BB has several predecessors, use a PHINode to select
       // the correct counter.
       for (auto &BB : F) {
         const unsigned EdgeCount =
             std::distance(pred_begin(&BB), pred_end(&BB));
         if (EdgeCount) {
           // The phi node must be at the begin of the BB.
           IRBuilder<> BuilderForPhi(&*BB.begin());
for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
 
     // Initialize the environment and register the local writeout, flush and
     // reset functions.
     FunctionCallee GCOVInit = M->getOrInsertFunction("llvm_gcov_init", FTy);
     Builder.CreateCall(GCOVInit, {WriteoutF, FlushF, ResetF});
     Builder.CreateRetVoid();
 
     appendToGlobalCtors(*M, F, 0);
+    Result = true;
   }
 
   return Result;
 }
 
 FunctionCallee GCOVProfiler::getStartFileFunc(const TargetLibraryInfo *TLI) {
   Type *Args[] = {
       Type::getInt8PtrTy(*Ctx), // const char *orig_filename