diff --git a/mlir/include/mlir/IR/OpBase.td b/mlir/include/mlir/IR/OpBase.td
--- a/mlir/include/mlir/IR/OpBase.td
+++ b/mlir/include/mlir/IR/OpBase.td
@@ -791,12 +791,16 @@
   // instantiation.
   // TOOD(b/132458159): deduplicate the fields in attribute wrapper classes.
   Attr baseAttr = ?;
+
+  // The fully-qualified C++ namespace where the generated class lives.
+  string cppNamespace = "";
 }
 
 // An attribute of a specific dialect.
 class DialectAttr<Dialect d, Pred condition, string descr = ""> :
     Attr<condition, descr> {
   Dialect dialect = d;
+  let cppNamespace = d.cppNamespace;
 }
 
 //===----------------------------------------------------------------------===//
@@ -1115,16 +1119,6 @@
   // underlying type is not explicitly specified.
   string underlyingType = "";
 
-  // The C++ namespaces that the enum class definition and utility functions
-  // should be placed into.
-  //
-  // Normally you want to place the full namespace path here. If it is nested,
-  // use "::" as the delimiter, e.g., given "A::B", generated code will be
-  // placed in `namespace A { namespace B { ... } }`. To avoid placing in any
-  // namespace, use "".
-  // TODO: use dialect to provide the namespace.
-  string cppNamespace = "";
-
   // The name of the utility function that converts a value of the underlying
   // type to the corresponding symbol. It will have the following signature:
   //
@@ -1463,7 +1457,8 @@
 // useful when representing data that would normally be in a structure.
 class StructAttr<string name, Dialect d,
                  list<StructFieldAttr> attributes> :
-    DictionaryAttrBase<CPred<"$_self.isa<" # name # ">()">,
+    DictionaryAttrBase<CPred<"$_self.isa<" # d.cppNamespace
+                                           # "::" # name # ">()">,
         "DictionaryAttr with field(s): " #
         StrJoin<!foreach(a, attributes, "'" # a.name # "'"), ", ">.result #
         " (each field having its own constraints)"> {
@@ -1471,14 +1466,16 @@
   string className = name;
 
   // Return type should match the name of the structure.
-  let returnType = name;
+  let returnType = d.cppNamespace # "::" # name;
 
   // Storage type should match the name of the structure.
-  let storageType = name;
+  let storageType = d.cppNamespace # "::" # name;
 
   // The dialect this StructAttr belongs to.
   Dialect dialect = d;
 
+  let cppNamespace = d.cppNamespace;
+
   // List of fields that the StructAttr contains.
   list<StructFieldAttr> fields = attributes;
 }
diff --git a/mlir/lib/TableGen/Pattern.cpp b/mlir/lib/TableGen/Pattern.cpp
--- a/mlir/lib/TableGen/Pattern.cpp
+++ b/mlir/lib/TableGen/Pattern.cpp
@@ -219,11 +219,11 @@
   case Kind::Operand: {
     // Use operand range for captured operands (to support potential variadic
     // operands).
-    return std::string(
-        formatv("Operation::operand_range {0}(op0->getOperands());\n", name));
+    return std::string(formatv(
+        "::mlir::Operation::operand_range {0}(op0->getOperands());\n", name));
   }
   case Kind::Value: {
-    return std::string(formatv("ArrayRef<Value> {0};\n", name));
+    return std::string(formatv("::llvm::ArrayRef<::mlir::Value> {0};\n", name));
   }
   case Kind::Result: {
     // Use the op itself for captured results.
diff --git a/mlir/tools/mlir-tblgen/OpDefinitionsGen.cpp b/mlir/tools/mlir-tblgen/OpDefinitionsGen.cpp
--- a/mlir/tools/mlir-tblgen/OpDefinitionsGen.cpp
+++ b/mlir/tools/mlir-tblgen/OpDefinitionsGen.cpp
@@ -487,16 +487,7 @@
 
   // Emit with return type specified.
   auto emitAttrWithReturnType = [&](StringRef name, Attribute attr) {
-    Dialect attrDialect = attr.getDialect();
-    // Does the current operation have a different namespace than the attribute?
-    bool differentNamespace =
-        attrDialect && opDialect && attrDialect != opDialect;
-    std::string returnType = differentNamespace
-                                 ? (llvm::Twine(attrDialect.getCppNamespace()) +
-                                    "::" + attr.getReturnType())
-                                       .str()
-                                 : attr.getReturnType().str();
-    auto *method = opClass.addMethodAndPrune(returnType, name);
+    auto *method = opClass.addMethodAndPrune(attr.getReturnType(), name);
     auto &body = method->body();
     body << "  auto attr = " << name << "Attr();\n";
     if (attr.hasDefaultValue()) {
@@ -2000,8 +1991,8 @@
   opClass.addTrait("::mlir::OpAsmOpInterface::Trait");
 
   // Generate the right accessor for the number of results.
-  auto *method = opClass.addMethodAndPrune("void", "getAsmResultNames",
-                                           "OpAsmSetValueNameFn", "setNameFn");
+  auto *method = opClass.addMethodAndPrune(
+      "void", "getAsmResultNames", "::mlir::OpAsmSetValueNameFn", "setNameFn");
   auto &body = method->body();
   for (int i = 0; i != numResults; ++i) {
     body << "  auto resultGroup" << i << " = getODSResults(" << i << ");\n"
diff --git a/mlir/tools/mlir-tblgen/RewriterGen.cpp b/mlir/tools/mlir-tblgen/RewriterGen.cpp
--- a/mlir/tools/mlir-tblgen/RewriterGen.cpp
+++ b/mlir/tools/mlir-tblgen/RewriterGen.cpp
@@ -221,7 +221,8 @@
 
   int indent = 4 + 2 * depth;
   os.indent(indent) << formatv(
-      "auto castedOp{0} = dyn_cast_or_null<{1}>(op{0}); (void)castedOp{0};\n",
+      "auto castedOp{0} = ::llvm::dyn_cast_or_null<{1}>(op{0}); "
+      "(void)castedOp{0};\n",
       depth, op.getQualCppClassName());
   // Skip the operand matching at depth 0 as the pattern rewriter already does.
   if (depth != 0) {
@@ -535,7 +536,7 @@
       os << "\n// Rewrite\n";
       emitRewriteLogic();
 
-      os << "return success();\n";
+      os << "return ::mlir::success();\n";
     }
     os << "};\n";
   }
@@ -1145,8 +1146,8 @@
   }
 
   // Emit function to add the generated matchers to the pattern list.
-  os << "void LLVM_ATTRIBUTE_UNUSED populateWithGenerated(MLIRContext "
-        "*context, OwningRewritePatternList *patterns) {\n";
+  os << "void LLVM_ATTRIBUTE_UNUSED populateWithGenerated(::mlir::MLIRContext "
+        "*context, ::mlir::OwningRewritePatternList *patterns) {\n";
   for (const auto &name : rewriterNames) {
     os << "  patterns->insert<" << name << ">(context);\n";
   }