Correctly report modified status for AddressSanitizer

[serge-sans-paille]

Summary

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

[foad]

Looks obviously correct.

llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp

struct AddressSanitizer {
   Instruction *generateCrashCode(Instruction *InsertBefore, Value *Addr,
                                  bool IsWrite, size_t AccessSizeIndex,
                                  Value *SizeArgument, uint32_t Exp);
   void instrumentMemIntrinsic(MemIntrinsic *MI);
   Value *memToShadow(Value *Shadow, IRBuilder<> &IRB);
   bool suppressInstrumentationSiteForDebug(int &Instrumented);
   bool instrumentFunction(Function &F, const TargetLibraryInfo *TLI);
   bool maybeInsertAsanInitAtFunctionEntry(Function &F);
-  void maybeInsertDynamicShadowAtFunctionEntry(Function &F);
+  bool maybeInsertDynamicShadowAtFunctionEntry(Function &F);
   void markEscapedLocalAllocas(Function &F);
 
 private:
   friend struct FunctionStackPoisoner;
 
   void initializeCallbacks(Module &M);
 
   bool LooksLikeCodeInBug11395(Instruction *I);
FunctionCallee AsanInitFunction =
         declareSanitizerInitFunction(*F.getParent(), kAsanInitName, {});
     IRBuilder<> IRB(&F.front(), F.front().begin());
     IRB.CreateCall(AsanInitFunction, {});
     return true;
   }
   return false;
 }
 
-void AddressSanitizer::maybeInsertDynamicShadowAtFunctionEntry(Function &F) {
+bool AddressSanitizer::maybeInsertDynamicShadowAtFunctionEntry(Function &F) {
   // Generate code only when dynamic addressing is needed.
   if (Mapping.Offset != kDynamicShadowSentinel)
-    return;
+    return false;
 
   IRBuilder<> IRB(&F.front().front());
   if (Mapping.InGlobal) {
     if (ClWithIfuncSuppressRemat) {
       // An empty inline asm with input reg == output reg.
       // An opaque pointer-to-int cast, basically.
       InlineAsm *Asm = InlineAsm::get(
           FunctionType::get(IntptrTy, {AsanShadowGlobal->getType()}, false),
           StringRef(""), StringRef("=r,0"),
           /*hasSideEffects=*/false);
       LocalDynamicShadow =
           IRB.CreateCall(Asm, {AsanShadowGlobal}, ".asan.shadow");
     } else {
       LocalDynamicShadow =
           IRB.CreatePointerCast(AsanShadowGlobal, IntptrTy, ".asan.shadow");
     }
   } else {
     Value *GlobalDynamicAddress = F.getParent()->getOrInsertGlobal(
         kAsanShadowMemoryDynamicAddress, IntptrTy);
     LocalDynamicShadow = IRB.CreateLoad(IntptrTy, GlobalDynamicAddress);
   }
+  return true;
 }
 
 void AddressSanitizer::markEscapedLocalAllocas(Function &F) {
   // Find the one possible call to llvm.localescape and pre-mark allocas passed
   // to it as uninteresting. This assumes we haven't started processing allocas
   // yet. This check is done up front because iterating the use list in
   // isInterestingAlloca would be algorithmically slower.
   assert(ProcessedAllocas.empty() && "must process localescape before allocas");
bool AddressSanitizer::instrumentFunction(Function &F,
   if (!F.hasFnAttribute(Attribute::SanitizeAddress)) return FunctionModified;
 
   LLVM_DEBUG(dbgs() << "ASAN instrumenting:\n" << F << "\n");
 
   initializeCallbacks(*F.getParent());
 
   FunctionStateRAII CleanupObj(this);
 
-  maybeInsertDynamicShadowAtFunctionEntry(F);
+  FunctionModified |= maybeInsertDynamicShadowAtFunctionEntry(F);
 
   // We can't instrument allocas used with llvm.localescape. Only static allocas
   // can be passed to that intrinsic.
   markEscapedLocalAllocas(F);
 
   // We want to instrument every address only once per basic block (unless there
   // are calls between uses).
   SmallPtrSet<Value *, 16> TempsToInstrument;