Add comment explaining MSVC behavior that we follow

Author: Fznamznon

clang/lib/CodeGen/CGExprCXX.cpp

@@ -1206,6 +1206,13 @@ void CodeGenFunction::EmitNewArrayInitializer(
     EmitCXXAggrConstructorCall(Ctor, NumElements, CurPtr, CCE,
                                /*NewPointerIsChecked*/true,
                                CCE->requiresZeroInitialization());
+
+    // For MSVC vector deleting destructors support we record that for the class
+    // new[] was called. We try to optimize the code size and only emit vector
+    // deleting destructors when they are required. Vector deleting destructors
+    // are required for delete[] call but MSVC triggers emission of them
+    // whenever new[] is called for an object of the class and we do the same
+    // for compatibility.
     if (CGM.getContext().getTargetInfo().emitVectorDeletingDtors(
             CGM.getContext().getLangOpts()))
       CGM.requireVectorDestructorDefinition(Ctor->getParent());