Itanium Mangling: Mangle `__alignof__` differently than `alignof`.

The two operations have acted differently since Clang 8, but were
unfortunately mangled the same. The new mangling uses new "vendor
extended expression" syntax proposed in
https://github.com/itanium-cxx-abi/cxx-abi/issues/112

GCC had the same mangling problem, https://gcc.gnu.org/PR88115, and
will hopefully be switching to the same mangling as implemented here.

Additionally, fix the mangling of `__uuidof` to use the new extension
syntax, instead of its previous nonstandard special-case.

Adjusts the demangler accordingly.

Differential Revision: https://reviews.llvm.org/D93922

GitOrigin-RevId: 9c7aeaebb3ac1b94200b59b111742cb6b8f090c2

src/demangle/ItaniumDemangle.h

diff --git a/src/demangle/ItaniumDemangle.h b/src/demangle/ItaniumDemangle.h
index 6bfc02d..e5fca98 100644
--- a/src/demangle/ItaniumDemangle.h
+++ b/src/demangle/ItaniumDemangle.h
@@ -96,7 +96,6 @@
     X(InitListExpr) \
     X(FoldExpr) \
     X(ThrowExpr) \
-    X(UUIDOfExpr) \
     X(BoolExpr) \
     X(StringLiteral) \
     X(LambdaExpr) \
@@ -2035,21 +2034,6 @@
   }
 };
 
-// MSVC __uuidof extension, generated by clang in -fms-extensions mode.
-class UUIDOfExpr : public Node {
-  Node *Operand;
-public:
-  UUIDOfExpr(Node *Operand_) : Node(KUUIDOfExpr), Operand(Operand_) {}
-
-  template<typename Fn> void match(Fn F) const { F(Operand); }
-
-  void printLeft(OutputStream &S) const override {
-    S << "__uuidof(";
-    Operand->print(S);
-    S << ")";
-  }
-};
-
 class BoolExpr : public Node {
   bool Value;
 
@@ -5013,6 +4997,43 @@
     }
     }
     return nullptr;
+  case 'u': {
+    ++First;
+    Node *Name = getDerived().parseSourceName(/*NameState=*/nullptr);
+    if (!Name)
+      return nullptr;
+    // Special case legacy __uuidof mangling. The 't' and 'z' appear where the
+    // standard encoding expects a <template-arg>, and would be otherwise be
+    // interpreted as <type> node 'short' or 'ellipsis'. However, neither
+    // __uuidof(short) nor __uuidof(...) can actually appear, so there is no
+    // actual conflict here.
+    if (Name->getBaseName() == "__uuidof") {
+      if (numLeft() < 2)
+        return nullptr;
+      if (*First == 't') {
+        ++First;
+        Node *Ty = getDerived().parseType();
+        if (!Ty)
+          return nullptr;
+        return make<CallExpr>(Name, makeNodeArray(&Ty, &Ty + 1));
+      }
+      if (*First == 'z') {
+        ++First;
+        Node *Ex = getDerived().parseExpr();
+        if (!Ex)
+          return nullptr;
+        return make<CallExpr>(Name, makeNodeArray(&Ex, &Ex + 1));
+      }
+    }
+    size_t ExprsBegin = Names.size();
+    while (!consumeIf('E')) {
+      Node *E = getDerived().parseTemplateArg();
+      if (E == nullptr)
+        return E;
+      Names.push_back(E);
+    }
+    return make<CallExpr>(Name, popTrailingNodeArray(ExprsBegin));
+  }
   case '1':
   case '2':
   case '3':
@@ -5024,21 +5045,6 @@
   case '9':
     return getDerived().parseUnresolvedName();
   }
-
-  if (consumeIf("u8__uuidoft")) {
-    Node *Ty = getDerived().parseType();
-    if (!Ty)
-      return nullptr;
-    return make<UUIDOfExpr>(Ty);
-  }
-
-  if (consumeIf("u8__uuidofz")) {
-    Node *Ex = getDerived().parseExpr();
-    if (!Ex)
-      return nullptr;
-    return make<UUIDOfExpr>(Ex);
-  }
-
   return nullptr;
 }
 

test/test_demangle.pass.cpp

diff --git a/test/test_demangle.pass.cpp b/test/test_demangle.pass.cpp
index 3954fdb..512cc39 100644
--- a/test/test_demangle.pass.cpp
+++ b/test/test_demangle.pass.cpp
@@ -29776,8 +29776,18 @@
     // Vendor extension types are substitution candidates.
     {"_Z1fu3fooS_", "f(foo, foo)"},
 
-    {"_ZN3FooIXu8__uuidofzdeL_Z3sucEEEC1Ev", "Foo<__uuidof(*(suc))>::Foo()"},
-    {"_ZN3FooIXu8__uuidoft13SomeUUIDClassEEC1Ev", "Foo<__uuidof(SomeUUIDClass)>::Foo()"},
+    // alignof with type and expression, and __alignof__ with the same.
+    {"_Z2f1IiEvDTatT_E", "void f1<int>(decltype(alignof (int)))"},
+    {"_Z2f3IiEvDTazcvT_Li0EE", "void f3<int>(decltype(alignof ((int)(0))))"},
+    {"_Z2f2IiEvDTu11__alignof__T_EE", "void f2<int>(decltype(__alignof__(int)))"},
+    {"_Z2f4IiEvDTu11__alignof__XcvT_Li0EEEE", "void f4<int>(decltype(__alignof__((int)(0))))"},
+
+    // Legacy nonstandard mangling for __uuidof.
+    {"_Z15test_uuidofTypeI10TestStructEvDTu8__uuidoftT_E", "void test_uuidofType<TestStruct>(decltype(__uuidof(TestStruct)))"},
+    {"_Z15test_uuidofExprI9HasMemberEvDTu8__uuidofXsrT_6memberEEE", "void test_uuidofExpr<HasMember>(decltype(__uuidof(HasMember::member)))"},
+    // Current __uuidof mangling using vendor extended expression.
+    {"_Z15test_uuidofTypeI10TestStructEvDTu8__uuidofT_EE", "void test_uuidofType<TestStruct>(decltype(__uuidof(TestStruct)))"},
+    {"_Z15test_uuidofExprI9HasMemberEvDTu8__uuidofXsrT_6memberEEE", "void test_uuidofExpr<HasMember>(decltype(__uuidof(HasMember::member)))"},
 
     // C++2a char8_t:
     {"_ZTSPDu", "typeinfo name for char8_t*"},