diff --git a/llvm/include/llvm/Demangle/ItaniumDemangle.h b/llvm/include/llvm/Demangle/ItaniumDemangle.h
--- a/llvm/include/llvm/Demangle/ItaniumDemangle.h
+++ b/llvm/include/llvm/Demangle/ItaniumDemangle.h
@@ -527,6 +527,23 @@
   }
 };
 
+class TransformedType : public Node {
+  StringView Transform;
+  Node *BaseType;
+public:
+  TransformedType(StringView Transform_, Node *BaseType_)
+      : Node(KTransformedType), Transform(Transform_), BaseType(BaseType_) {}
+
+  template<typename Fn> void match(Fn F) const { F(Transform, BaseType); }
+
+  void printLeft(OutputBuffer &OB) const override {
+    OB += Transform;
+    OB += '(';
+    BaseType->print(OB);
+    OB += ')';
+  }
+};
+
 struct AbiTagAttr : Node {
   Node *Base;
   StringView Tag;
@@ -3884,7 +3901,15 @@
     // Typically, <builtin-type>s are not considered substitution candidates,
     // but the exception to that exception is vendor extended types (Itanium C++
     // ABI 5.9.1).
-    Result = make<NameType>(Res);
+    if (consumeIf('I')) {
+      Node *BaseType = parseType();
+      if (BaseType == nullptr)
+        return nullptr;
+      if (!consumeIf('E'))
+        return nullptr;
+      Result = make<TransformedType>(Res, BaseType);
+    } else
+      Result = make<NameType>(Res);
     break;
   }
   case 'D':
diff --git a/llvm/include/llvm/Demangle/ItaniumNodes.def b/llvm/include/llvm/Demangle/ItaniumNodes.def
--- a/llvm/include/llvm/Demangle/ItaniumNodes.def
+++ b/llvm/include/llvm/Demangle/ItaniumNodes.def
@@ -19,6 +19,7 @@
 NODE(ConversionOperatorType)
 NODE(PostfixQualifiedType)
 NODE(ElaboratedTypeSpefType)
+NODE(TransformedType)
 NODE(NameType)
 NODE(AbiTagAttr)
 NODE(EnableIfAttr)
diff --git a/llvm/unittests/Demangle/ItaniumDemangleTest.cpp b/llvm/unittests/Demangle/ItaniumDemangleTest.cpp
--- a/llvm/unittests/Demangle/ItaniumDemangleTest.cpp
+++ b/llvm/unittests/Demangle/ItaniumDemangleTest.cpp
@@ -56,6 +56,11 @@
 }
 } // namespace NodeMatcher
 
+static std::string toString(OutputBuffer &OB) {
+  StringView SV = OB;
+  return {SV.begin(), SV.end()};
+}
+
 // Verify Operator table is ordered
 TEST(ItaniumDemangle, OperatorOrdering) {
   struct TestParser : AbstractManglingParser<TestParser, TestAllocator> {};
@@ -82,9 +87,24 @@
   EXPECT_THAT(Parser.Types, testing::ElementsAre('i', 'j', 'l'));
 }
 
-static std::string toString(OutputBuffer &OB) {
-  StringView SV = OB;
-  return {SV.begin(), SV.end()};
+TEST(ItaniumDemangle, TransformedType) {
+  struct TestParser : AbstractManglingParser<TestParser, TestAllocator> {
+    std::vector<std::string> Types;
+    TestParser(const char *Str)
+        : AbstractManglingParser(Str, Str + strlen(Str)) {}
+    Node *parseType() {
+      Node *N = AbstractManglingParser<TestParser, TestAllocator>::parseType();
+      OutputBuffer OB;
+      N->print(OB);
+      Types.push_back(toString(OB));
+      return N;
+    }
+  };
+
+  TestParser Parser("_Z2f5IiEvu7__decayIT_E");
+  ASSERT_NE(nullptr, Parser.parse());
+  EXPECT_THAT(Parser.Types,
+              testing::ElementsAre("int", "void", "__decay(int)"));
 }
 
 TEST(ItaniumDemangle, HalfType) {