Fix UB passing nullptr to an EmptyProperties class when building OpAdaptor

[mehdi_amini]

Summary

A new forwarding constructor is introduced on the adaptor to take directly
an OpaqueProperties object and do the nullptr checking and casting to avoid
the boilerplate at callsites.

mlir/lib/Dialect/MemRef/IR/MemRefOps.cpp

 //===----------------------------------------------------------------------===//
 
 /// The number and type of the results are inferred from the
 /// shape of the source.
 LogicalResult ExtractStridedMetadataOp::inferReturnTypes(
     MLIRContext *context, std::optional<Location> location, ValueRange operands,
     DictionaryAttr attributes, OpaqueProperties properties, RegionRange regions,
     SmallVectorImpl<Type> &inferredReturnTypes) {
-  ExtractStridedMetadataOpAdaptor extractAdaptor(
-      operands, attributes, *properties.as<EmptyProperties *>(), regions);
+  ExtractStridedMetadataOpAdaptor extractAdaptor(operands, attributes,
+                                                 properties);
   auto sourceType = extractAdaptor.getSource().getType().dyn_cast<MemRefType>();
   if (!sourceType)
     return failure();
 
   unsigned sourceRank = sourceType.getRank();
   IndexType indexType = IndexType::get(context);
   auto memrefType =
       MemRefType::get({}, sourceType.getElementType(),

mlir/test/mlir-tblgen/op-decl-and-defs.td

 // CHECK:   static void getCanonicalizationPatterns(::mlir::RewritePatternSet &results, ::mlir::MLIRContext *context);
 // CHECK:   ::mlir::LogicalResult fold(FoldAdaptor adaptor, ::llvm::SmallVectorImpl<::mlir::OpFoldResult> &results);
 // CHECK:   // Display a graph for debugging purposes.
 // CHECK:   void displayGraph();
 // CHECK: };
 
 // DEFS-LABEL: NS::AOp definitions
 
-// DEFS: AOpGenericAdaptorBase::AOpGenericAdaptorBase(::mlir::DictionaryAttr attrs, ::mlir::EmptyProperties properties, ::mlir::RegionRange regions) : odsAttrs(attrs), odsRegions(regions)
+// DEFS: AOpGenericAdaptorBase::AOpGenericAdaptorBase(::mlir::DictionaryAttr attrs, const ::mlir::EmptyProperties &properties, ::mlir::RegionRange regions) : odsAttrs(attrs), odsRegions(regions)
 // DEFS: ::mlir::RegionRange AOpGenericAdaptorBase::getSomeRegions()
 // DEFS-NEXT: return odsRegions.drop_front(1);
 // DEFS: ::mlir::RegionRange AOpGenericAdaptorBase::getRegions()
 
 // Check AttrSizedOperandSegments
 // ---
 
 def NS_AttrSizedOperandOp : NS_Op<"attr_sized_operands",

mlir/tools/mlir-tblgen/OpDefinitionsGen.cpp

const auto *attrSizedOperands =
       op.getTrait("::mlir::OpTrait::AttrSizedOperandSegments");
   {
     SmallVector<MethodParameter> paramList;
     paramList.emplace_back("::mlir::DictionaryAttr", "attrs",
                            attrSizedOperands ? "" : "nullptr");
     if (useProperties)
       paramList.emplace_back("const Properties &", "properties", "{}");
     else
-      paramList.emplace_back("::mlir::EmptyProperties", "properties", "{}");
+      paramList.emplace_back("const ::mlir::EmptyProperties &", "properties",
+                             "{}");
     paramList.emplace_back("::mlir::RegionRange", "regions", "{}");
     auto *baseConstructor = genericAdaptorBase.addConstructor(paramList);
     baseConstructor->addMemberInitializer("odsAttrs", "attrs");
     if (useProperties)
       baseConstructor->addMemberInitializer("properties", "properties");
     baseConstructor->addMemberInitializer("odsRegions", "regions");
 
     MethodBody &body = baseConstructor->body();
     body.indent() << "if (odsAttrs)\n";
     body.indent() << formatv(
         "odsOpName.emplace(\"{0}\", odsAttrs.getContext());\n",
         op.getOperationName());
 
     paramList.insert(paramList.begin(), MethodParameter("RangeT", "values"));
-    auto *constructor = genericAdaptor.addConstructor(std::move(paramList));
+    auto *constructor = genericAdaptor.addConstructor(paramList);
     constructor->addMemberInitializer("Base", "attrs, properties, regions");
     constructor->addMemberInitializer("odsOperands", "values");
+
+    // Add a forwarding constructor to the previous one that accepts
+    // OpaqueProperties instead and check for null and perform the cast to the
+    // actual properties type.
+    paramList[1] = MethodParameter("::mlir::DictionaryAttr", "attrs");
+    paramList[2] = MethodParameter("::mlir::OpaqueProperties", "properties");
+    auto *opaquePropertiesConstructor =
+        genericAdaptor.addConstructor(std::move(paramList));
+    if (useProperties) {
+      opaquePropertiesConstructor->addMemberInitializer(
+          genericAdaptor.getClassName(),
+          "values, "
+          "attrs, "
+          "(properties ? *properties.as<Properties *>() : Properties{}), "
+          "regions");
+    } else {
+      opaquePropertiesConstructor->addMemberInitializer(
+          genericAdaptor.getClassName(),
+          "values, "
+          "attrs, "
+          "(properties ? *properties.as<::mlir::EmptyProperties *>() : "
+          "::mlir::EmptyProperties{}), "
+          "regions");
+    }
   }
 
   std::string sizeAttrInit;
   if (op.getTrait("::mlir::OpTrait::AttrSizedOperandSegments")) {
     sizeAttrInit = formatv(adapterSegmentSizeAttrInitCode,
                            emitHelper.getAttr(operandSegmentAttrName));
   }
   generateNamedOperandGetters(op, genericAdaptor,