diff --git a/libcxxabi/src/demangle/ItaniumDemangle.h b/libcxxabi/src/demangle/ItaniumDemangle.h
--- a/libcxxabi/src/demangle/ItaniumDemangle.h
+++ b/libcxxabi/src/demangle/ItaniumDemangle.h
@@ -82,6 +82,7 @@
     X(PostfixExpr) \
     X(ConditionalExpr) \
     X(MemberExpr) \
+    X(SubobjectExpr) \
     X(EnclosingExpr) \
     X(CastExpr) \
     X(SizeofParamPackExpr) \
@@ -91,6 +92,7 @@
     X(PrefixExpr) \
     X(FunctionParam) \
     X(ConversionExpr) \
+    X(PointerToMemberConversionExpr) \
     X(InitListExpr) \
     X(FoldExpr) \
     X(ThrowExpr) \
@@ -1656,6 +1658,40 @@
   }
 };
 
+class SubobjectExpr : public Node {
+  const Node *Type;
+  const Node *SubExpr;
+  StringView Offset;
+  NodeArray UnionSelectors;
+  bool OnePastTheEnd;
+
+public:
+  SubobjectExpr(const Node *Type_, const Node *SubExpr_, StringView Offset_,
+                NodeArray UnionSelectors_, bool OnePastTheEnd_)
+      : Node(KSubobjectExpr), Type(Type_), SubExpr(SubExpr_), Offset(Offset_),
+        UnionSelectors(UnionSelectors_), OnePastTheEnd(OnePastTheEnd_) {}
+
+  template<typename Fn> void match(Fn F) const {
+    F(Type, SubExpr, Offset, UnionSelectors, OnePastTheEnd);
+  }
+
+  void printLeft(OutputStream &S) const override {
+    SubExpr->print(S);
+    S += ".<";
+    Type->print(S);
+    S += " at offset ";
+    if (Offset.empty()) {
+      S += "0";
+    } else if (Offset[0] == 'n') {
+      S += "-";
+      S += Offset.dropFront();
+    } else {
+      S += Offset;
+    }
+    S += ">";
+  }
+};
+
 class EnclosingExpr : public Node {
   const StringView Prefix;
   const Node *Infix;
@@ -1843,6 +1879,28 @@
   }
 };
 
+class PointerToMemberConversionExpr : public Node {
+  const Node *Type;
+  const Node *SubExpr;
+  StringView Offset;
+
+public:
+  PointerToMemberConversionExpr(const Node *Type_, const Node *SubExpr_,
+                                StringView Offset_)
+      : Node(KPointerToMemberConversionExpr), Type(Type_), SubExpr(SubExpr_),
+        Offset(Offset_) {}
+
+  template<typename Fn> void match(Fn F) const { F(Type, SubExpr, Offset); }
+
+  void printLeft(OutputStream &S) const override {
+    S += "(";
+    Type->print(S);
+    S += ")(";
+    SubExpr->print(S);
+    S += ")";
+  }
+};
+
 class InitListExpr : public Node {
   const Node *Ty;
   NodeArray Inits;
@@ -2437,6 +2495,8 @@
   Node *parseConversionExpr();
   Node *parseBracedExpr();
   Node *parseFoldExpr();
+  Node *parsePointerToMemberConversionExpr();
+  Node *parseSubobjectExpr();
 
   /// Parse the <type> production.
   Node *parseType();
@@ -4404,6 +4464,50 @@
   return make<FoldExpr>(IsLeftFold, OperatorName, Pack, Init);
 }
 
+// <expression> ::= mc <parameter type> <expr> [<offset number>] E
+//
+// Not yet in the spec: https://github.com/itanium-cxx-abi/cxx-abi/issues/47
+template <typename Derived, typename Alloc>
+Node *AbstractManglingParser<Derived, Alloc>::parsePointerToMemberConversionExpr() {
+  Node *Ty = getDerived().parseType();
+  if (!Ty)
+    return nullptr;
+  Node *Expr = getDerived().parseExpr();
+  if (!Expr)
+    return nullptr;
+  StringView Offset = getDerived().parseNumber(true);
+  if (!consumeIf('E'))
+    return nullptr;
+  return make<PointerToMemberConversionExpr>(Ty, Expr, Offset);
+}
+
+// <expression> ::= so <referent type> <expr> [<offset number>] <union-selector>* [p] E
+// <union-selector> ::= _ [<number>]
+//
+// Not yet in the spec: https://github.com/itanium-cxx-abi/cxx-abi/issues/47
+template <typename Derived, typename Alloc>
+Node *AbstractManglingParser<Derived, Alloc>::parseSubobjectExpr() {
+  Node *Ty = getDerived().parseType();
+  if (!Ty)
+    return nullptr;
+  Node *Expr = getDerived().parseExpr();
+  if (!Expr)
+    return nullptr;
+  StringView Offset = getDerived().parseNumber(true);
+  size_t SelectorsBegin = Names.size();
+  while (consumeIf('_')) {
+    Node *Selector = make<NameType>(parseNumber());
+    if (!Selector)
+      return nullptr;
+    Names.push_back(Selector);
+  }
+  bool OnePastTheEnd = consumeIf('p');
+  if (!consumeIf('E'))
+    return nullptr;
+  return make<SubobjectExpr>(
+      Ty, Expr, Offset, popTrailingNodeArray(SelectorsBegin), OnePastTheEnd);
+}
+
 // <expression> ::= <unary operator-name> <expression>
 //              ::= <binary operator-name> <expression> <expression>
 //              ::= <ternary operator-name> <expression> <expression> <expression>
@@ -4661,6 +4765,9 @@
     return nullptr;
   case 'm':
     switch (First[1]) {
+    case 'c':
+      First += 2;
+      return parsePointerToMemberConversionExpr();
     case 'i':
       First += 2;
       return getDerived().parseBinaryExpr("-");
@@ -4808,6 +4915,9 @@
         return Ex;
       return make<CastExpr>("static_cast", T, Ex);
     }
+    case 'o':
+      First += 2;
+      return parseSubobjectExpr();
     case 'p': {
       First += 2;
       Node *Child = getDerived().parseExpr();
@@ -4975,6 +5085,16 @@
   switch (look()) {
   case 'T':
     switch (look(1)) {
+    // TA <template-arg>    # template parameter object
+    //
+    // Not yet in the spec: https://github.com/itanium-cxx-abi/cxx-abi/issues/63
+    case 'A': {
+      First += 2;
+      Node *Arg = getDerived().parseTemplateArg();
+      if (Arg == nullptr)
+        return nullptr;
+      return make<SpecialName>("template parameter object for ", Arg);
+    }
     // TV <type>    # virtual table
     case 'V': {
       First += 2;
diff --git a/libcxxabi/test/test_demangle.pass.cpp b/libcxxabi/test/test_demangle.pass.cpp
--- a/libcxxabi/test/test_demangle.pass.cpp
+++ b/libcxxabi/test/test_demangle.pass.cpp
@@ -29800,6 +29800,21 @@
     {"_ZN1XIZ1fIiEvOT_EUlS2_DpT0_E_EclIJEEEvDpT_", "void X<void f<int>(int&&)::'lambda'(int&&, auto...)>::operator()<>()"},
     {"_ZZZZN6abcdef9abcdefghi29abcdefabcdefabcdefabcefabcdef27xxxxxxxxxxxxxxxxxxxxxxxxxxxEN4absl8DurationERKNSt3__u12basic_stringIcNS4_11char_traitsIcEENS4_9allocatorIcEEEEPNS1_19yyyyyyyyyyyyyyyyyyyEENK3$_5clEvENKUlvE_clEvE6zzzzzz", "abcdef::abcdefghi::abcdefabcdefabcdefabcefabcdef::xxxxxxxxxxxxxxxxxxxxxxxxxxx(absl::Duration, std::__u::basic_string<char, std::__u::char_traits<char>, std::__u::allocator<char> > const&, abcdef::abcdefghi::abcdefabcdefabcdefabcefabcdef::yyyyyyyyyyyyyyyyyyy*)::$_5::operator()() const::'lambda'()::operator()() const::zzzzzz"},
 
+    // C++2a class type non-type template parameters:
+    {"_Z1fIXtl1BLPi0ELi1EEEEvv", "void f<B{(int*)0, 1}>()"},
+    {"_Z1fIXtl1BLPi32EEEEvv", "void f<B{(int*)32}>()"},
+    {"_Z1fIXtl1BrcPiLi0EEEEvv", "void f<B{reinterpret_cast<int*>(0)}>()"},
+    {"_Z1fIXtl1BadsoiL_Z6nestedE_EEEEvv", "void f<B{&(nested.<int at offset 0>)}>()"},
+    {"_Z1fIXtl1BadsoiL_Z6nestedE16_0pEEEEvv", "void f<B{&(nested.<int at offset 16>)}>()"},
+    {"_Z1fIXtl2BRsoiL_Z7derivedE4EEEEvv", "void f<BR{derived.<int at offset 4>}>()"},
+    {"_Z1fIXtl1BcvPiplcvPcadL_Z7derivedELl16EEEEvv", "void f<B{(int*)(((char*)(&(derived))) + (16l))}>()"},
+    {"_Z1fIXtl1CadsoKiL_Z7derivedE4EEEEvv", "void f<C{&(derived.<int const at offset 4>)}>()"},
+    {"_Z1fIXtl1DLM7DerivedKi0ELi1EEEEvv", "void f<D{(int const Derived::*)0, 1}>()"},
+    // FIXME: This is not valid pointer-to-member syntax.
+    {"_Z1fIXtl1DmcM7DerivedKiadL_ZN11MoreDerived1zEEn8EEEEvv", "void f<D{(int const Derived::*)(&(MoreDerived::z))}>()"},
+    {"_Z1fIXtl1Edi1nLi42EEEEvv", "void f<E{.n = 42}>()"},
+    {"_ZTAXtl1StlA32_cLc104ELc101ELc108ELc108ELc111ELc32ELc119ELc111ELc114ELc108ELc100EEEE", "template parameter object for S{char [32]{(char)104, (char)101, (char)108, (char)108, (char)111, (char)32, (char)119, (char)111, (char)114, (char)108, (char)100}}"},
+
     // FIXME: This is wrong; the S2_ backref should expand to OT_ and then to
     // "double&&". But we can't cope with a substitution that represents a
     // different type the node it is a substitute for.
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
@@ -82,6 +82,7 @@
     X(PostfixExpr) \
     X(ConditionalExpr) \
     X(MemberExpr) \
+    X(SubobjectExpr) \
     X(EnclosingExpr) \
     X(CastExpr) \
     X(SizeofParamPackExpr) \
@@ -91,6 +92,7 @@
     X(PrefixExpr) \
     X(FunctionParam) \
     X(ConversionExpr) \
+    X(PointerToMemberConversionExpr) \
     X(InitListExpr) \
     X(FoldExpr) \
     X(ThrowExpr) \
@@ -1656,6 +1658,40 @@
   }
 };
 
+class SubobjectExpr : public Node {
+  const Node *Type;
+  const Node *SubExpr;
+  StringView Offset;
+  NodeArray UnionSelectors;
+  bool OnePastTheEnd;
+
+public:
+  SubobjectExpr(const Node *Type_, const Node *SubExpr_, StringView Offset_,
+                NodeArray UnionSelectors_, bool OnePastTheEnd_)
+      : Node(KSubobjectExpr), Type(Type_), SubExpr(SubExpr_), Offset(Offset_),
+        UnionSelectors(UnionSelectors_), OnePastTheEnd(OnePastTheEnd_) {}
+
+  template<typename Fn> void match(Fn F) const {
+    F(Type, SubExpr, Offset, UnionSelectors, OnePastTheEnd);
+  }
+
+  void printLeft(OutputStream &S) const override {
+    SubExpr->print(S);
+    S += ".<";
+    Type->print(S);
+    S += " at offset ";
+    if (Offset.empty()) {
+      S += "0";
+    } else if (Offset[0] == 'n') {
+      S += "-";
+      S += Offset.dropFront();
+    } else {
+      S += Offset;
+    }
+    S += ">";
+  }
+};
+
 class EnclosingExpr : public Node {
   const StringView Prefix;
   const Node *Infix;
@@ -1843,6 +1879,28 @@
   }
 };
 
+class PointerToMemberConversionExpr : public Node {
+  const Node *Type;
+  const Node *SubExpr;
+  StringView Offset;
+
+public:
+  PointerToMemberConversionExpr(const Node *Type_, const Node *SubExpr_,
+                                StringView Offset_)
+      : Node(KPointerToMemberConversionExpr), Type(Type_), SubExpr(SubExpr_),
+        Offset(Offset_) {}
+
+  template<typename Fn> void match(Fn F) const { F(Type, SubExpr, Offset); }
+
+  void printLeft(OutputStream &S) const override {
+    S += "(";
+    Type->print(S);
+    S += ")(";
+    SubExpr->print(S);
+    S += ")";
+  }
+};
+
 class InitListExpr : public Node {
   const Node *Ty;
   NodeArray Inits;
@@ -2437,6 +2495,8 @@
   Node *parseConversionExpr();
   Node *parseBracedExpr();
   Node *parseFoldExpr();
+  Node *parsePointerToMemberConversionExpr();
+  Node *parseSubobjectExpr();
 
   /// Parse the <type> production.
   Node *parseType();
@@ -4404,6 +4464,50 @@
   return make<FoldExpr>(IsLeftFold, OperatorName, Pack, Init);
 }
 
+// <expression> ::= mc <parameter type> <expr> [<offset number>] E
+//
+// Not yet in the spec: https://github.com/itanium-cxx-abi/cxx-abi/issues/47
+template <typename Derived, typename Alloc>
+Node *AbstractManglingParser<Derived, Alloc>::parsePointerToMemberConversionExpr() {
+  Node *Ty = getDerived().parseType();
+  if (!Ty)
+    return nullptr;
+  Node *Expr = getDerived().parseExpr();
+  if (!Expr)
+    return nullptr;
+  StringView Offset = getDerived().parseNumber(true);
+  if (!consumeIf('E'))
+    return nullptr;
+  return make<PointerToMemberConversionExpr>(Ty, Expr, Offset);
+}
+
+// <expression> ::= so <referent type> <expr> [<offset number>] <union-selector>* [p] E
+// <union-selector> ::= _ [<number>]
+//
+// Not yet in the spec: https://github.com/itanium-cxx-abi/cxx-abi/issues/47
+template <typename Derived, typename Alloc>
+Node *AbstractManglingParser<Derived, Alloc>::parseSubobjectExpr() {
+  Node *Ty = getDerived().parseType();
+  if (!Ty)
+    return nullptr;
+  Node *Expr = getDerived().parseExpr();
+  if (!Expr)
+    return nullptr;
+  StringView Offset = getDerived().parseNumber(true);
+  size_t SelectorsBegin = Names.size();
+  while (consumeIf('_')) {
+    Node *Selector = make<NameType>(parseNumber());
+    if (!Selector)
+      return nullptr;
+    Names.push_back(Selector);
+  }
+  bool OnePastTheEnd = consumeIf('p');
+  if (!consumeIf('E'))
+    return nullptr;
+  return make<SubobjectExpr>(
+      Ty, Expr, Offset, popTrailingNodeArray(SelectorsBegin), OnePastTheEnd);
+}
+
 // <expression> ::= <unary operator-name> <expression>
 //              ::= <binary operator-name> <expression> <expression>
 //              ::= <ternary operator-name> <expression> <expression> <expression>
@@ -4661,6 +4765,9 @@
     return nullptr;
   case 'm':
     switch (First[1]) {
+    case 'c':
+      First += 2;
+      return parsePointerToMemberConversionExpr();
     case 'i':
       First += 2;
       return getDerived().parseBinaryExpr("-");
@@ -4808,6 +4915,9 @@
         return Ex;
       return make<CastExpr>("static_cast", T, Ex);
     }
+    case 'o':
+      First += 2;
+      return parseSubobjectExpr();
     case 'p': {
       First += 2;
       Node *Child = getDerived().parseExpr();
@@ -4975,6 +5085,16 @@
   switch (look()) {
   case 'T':
     switch (look(1)) {
+    // TA <template-arg>    # template parameter object
+    //
+    // Not yet in the spec: https://github.com/itanium-cxx-abi/cxx-abi/issues/63
+    case 'A': {
+      First += 2;
+      Node *Arg = getDerived().parseTemplateArg();
+      if (Arg == nullptr)
+        return nullptr;
+      return make<SpecialName>("template parameter object for ", Arg);
+    }
     // TV <type>    # virtual table
     case 'V': {
       First += 2;