[Demangle] demangle builtin type transformations

libcxxabi/src/demangle/ItaniumDemangle.h

@@ -534,6 +534,23 @@ class ElaboratedTypeSpefType : public Node {
   }
 };
 
+class TransformedType : public Node {
+  std::string_view Transform;
+  Node *BaseType;
+public:
+  TransformedType(std::string_view 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;
   std::string_view Tag;
@@ -3894,7 +3911,15 @@ Node *AbstractManglingParser<Derived, Alloc>::parseType() {
     // 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':

libcxxabi/src/demangle/ItaniumNodes.def

@@ -19,6 +19,7 @@ NODE(QualType)
 NODE(ConversionOperatorType)
 NODE(PostfixQualifiedType)
 NODE(ElaboratedTypeSpefType)
+NODE(TransformedType)
 NODE(NameType)
 NODE(AbiTagAttr)
 NODE(EnableIfAttr)

libcxxabi/test/test_demangle.pass.cpp

@@ -30114,6 +30114,9 @@ const char* cases[][2] =
      " std::allocator<char>>::basic_string()"},
     {"_ZN1SB8ctor_tagC2Ev", "S[abi:ctor_tag]::S()"},
     {"_ZN1SB8ctor_tagD2Ev", "S[abi:ctor_tag]::~S()"},
+
+    // clang builtin type transform
+    {"_Z2f5IiEvu7__decayIT_E", "void f5<int>(__decay(int))"},
 };
 
 const unsigned N = sizeof(cases) / sizeof(cases[0]);

llvm/include/llvm/Demangle/ItaniumDemangle.h

@@ -528,6 +528,23 @@ class ElaboratedTypeSpefType : public Node {
   }
 };
 
+class TransformedType : public Node {
+  std::string_view Transform;
+  Node *BaseType;
+public:
+  TransformedType(std::string_view 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;
   std::string_view Tag;
@@ -3889,7 +3906,15 @@ Node *AbstractManglingParser<Derived, Alloc>::parseType() {
     // 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':

llvm/include/llvm/Demangle/ItaniumNodes.def

@@ -19,6 +19,7 @@ NODE(QualType)
 NODE(ConversionOperatorType)
 NODE(PostfixQualifiedType)
 NODE(ElaboratedTypeSpefType)
+NODE(TransformedType)
 NODE(NameType)
 NODE(AbiTagAttr)
 NODE(EnableIfAttr)