[NFC][asan] Create ModuleName lazily (#104729)

Avoids tracking conditions when it's needed.

Author: vitalybuka

llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp

@@ -944,13 +944,14 @@ class ModuleAddressSanitizer {
   bool shouldInstrumentGlobal(GlobalVariable *G) const;
   bool ShouldUseMachOGlobalsSection() const;
   StringRef getGlobalMetadataSection() const;
-  void poisonOneInitializer(Function &GlobalInit, GlobalValue *ModuleName);
-  void createInitializerPoisonCalls(GlobalValue *ModuleName);
+  void poisonOneInitializer(Function &GlobalInit);
+  void createInitializerPoisonCalls();
   uint64_t getMinRedzoneSizeForGlobal() const {
     return getRedzoneSizeForScale(Mapping.Scale);
   }
   uint64_t getRedzoneSizeForGlobal(uint64_t SizeInBytes) const;
   int GetAsanVersion() const;
+  GlobalVariable *getOrCreateModuleName();
 
   Module &M;
   bool CompileKernel;
@@ -978,6 +979,7 @@ class ModuleAddressSanitizer {
 
   Function *AsanCtorFunction = nullptr;
   Function *AsanDtorFunction = nullptr;
+  GlobalVariable *ModuleName = nullptr;
 };
 
 // Stack poisoning does not play well with exception handling.
@@ -1965,14 +1967,14 @@ void AddressSanitizer::instrumentUnusualSizeOrAlignment(
   }
 }
 
-void ModuleAddressSanitizer::poisonOneInitializer(Function &GlobalInit,
-                                                  GlobalValue *ModuleName) {
+void ModuleAddressSanitizer::poisonOneInitializer(Function &GlobalInit) {
   // Set up the arguments to our poison/unpoison functions.
   IRBuilder<> IRB(&GlobalInit.front(),
                   GlobalInit.front().getFirstInsertionPt());
 
   // Add a call to poison all external globals before the given function starts.
-  Value *ModuleNameAddr = ConstantExpr::getPointerCast(ModuleName, IntptrTy);
+  Value *ModuleNameAddr =
+      ConstantExpr::getPointerCast(getOrCreateModuleName(), IntptrTy);
   IRB.CreateCall(AsanPoisonGlobals, ModuleNameAddr);
 
   // Add calls to unpoison all globals before each return instruction.
@@ -1981,8 +1983,7 @@ void ModuleAddressSanitizer::poisonOneInitializer(Function &GlobalInit,
       CallInst::Create(AsanUnpoisonGlobals, "", RI->getIterator());
 }
 
-void ModuleAddressSanitizer::createInitializerPoisonCalls(
-    GlobalValue *ModuleName) {
+void ModuleAddressSanitizer::createInitializerPoisonCalls() {
   GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors");
   if (!GV)
     return;
@@ -2002,7 +2003,7 @@ void ModuleAddressSanitizer::createInitializerPoisonCalls(
       // Don't instrument CTORs that will run before asan.module_ctor.
       if (Priority->getLimitedValue() <= GetCtorAndDtorPriority(TargetTriple))
         continue;
-      poisonOneInitializer(*F, ModuleName);
+      poisonOneInitializer(*F);
     }
   }
 }
@@ -2539,14 +2540,6 @@ void ModuleAddressSanitizer::instrumentGlobals(IRBuilder<> &IRB,
 
   bool HasDynamicallyInitializedGlobals = false;
 
-  // We shouldn't merge same module names, as this string serves as unique
-  // module ID in runtime.
-  GlobalVariable *ModuleName =
-      n != 0 ? createPrivateGlobalForString(M, M.getModuleIdentifier(),
-                                            /*AllowMerging*/ false,
-                                            genName("module"))
-             : nullptr;
-
   for (size_t i = 0; i < n; i++) {
     GlobalVariable *G = GlobalsToChange[i];
 
@@ -2647,7 +2640,7 @@ void ModuleAddressSanitizer::instrumentGlobals(IRBuilder<> &IRB,
         ConstantInt::get(IntptrTy, SizeInBytes),
         ConstantInt::get(IntptrTy, SizeInBytes + RightRedzoneSize),
         ConstantExpr::getPointerCast(Name, IntptrTy),
-        ConstantExpr::getPointerCast(ModuleName, IntptrTy),
+        ConstantExpr::getPointerCast(getOrCreateModuleName(), IntptrTy),
         ConstantInt::get(IntptrTy, MD.IsDynInit),
         Constant::getNullValue(IntptrTy),
         ConstantExpr::getPointerCast(ODRIndicator, IntptrTy));
@@ -2694,7 +2687,7 @@ void ModuleAddressSanitizer::instrumentGlobals(IRBuilder<> &IRB,
 
   // Create calls for poisoning before initializers run and unpoisoning after.
   if (HasDynamicallyInitializedGlobals)
-    createInitializerPoisonCalls(ModuleName);
+    createInitializerPoisonCalls();
 
   LLVM_DEBUG(dbgs() << M);
 }
@@ -2734,6 +2727,17 @@ int ModuleAddressSanitizer::GetAsanVersion() const {
   return Version;
 }
 
+GlobalVariable *ModuleAddressSanitizer::getOrCreateModuleName() {
+  if (!ModuleName) {
+    // We shouldn't merge same module names, as this string serves as unique
+    // module ID in runtime.
+    ModuleName =
+        createPrivateGlobalForString(M, M.getModuleIdentifier(),
+                                     /*AllowMerging*/ false, genName("module"));
+  }
+  return ModuleName;
+}
+
 bool ModuleAddressSanitizer::instrumentModule() {
   initializeCallbacks();