Index: llvm/lib/Demangle/DLangDemangle.cpp
===================================================================
--- llvm/lib/Demangle/DLangDemangle.cpp
+++ llvm/lib/Demangle/DLangDemangle.cpp
@@ -190,6 +190,18 @@
   /// \see https://dlang.org/spec/abi.html#function_calling_conventions
   bool isCallConvention(const char *Mangled);
 
+  /// Extract and demangle calling convention from a given mangled symbol and
+  /// append it to the output string
+  ///
+  /// \param Decl output buffer to write the demangled name
+  /// \param Mangled mangled symbol to be demangled
+  ///
+  /// \return the remaining string on success or nullptr on failure
+  ///
+  /// \see https://dlang.org/spec/abi.html#CallConvention
+  /// \see https://dlang.org/spec/abi.html#function_calling_conventions
+  const char *parseCallConvention(OutputString *Decl, const char *Mangled);
+
   /// Check whether it is the beginning of a symbol name
   ///
   /// \param Mangled string to extract the symbol name
@@ -235,6 +247,58 @@
   /// \see https://dlang.org/spec/abi.html#QualifiedName
   const char *parseQualified(OutputString *Decl, const char *Mangled);
 
+  /// Extract and demangle the D function attributes from a given mangled
+  /// symbol append it to the output string
+  ///
+  /// \param Decl output buffer to write the demangled name
+  /// \param Mangled mangled symbol to be demangled
+  ///
+  /// \return the remaining string on success or nullptr on failure
+  ///
+  /// \see https://dlang.org/spec/abi.html#FuncAttr
+  const char *parseAttributes(OutputString *Decl, const char *Mangled);
+
+  /// Extract and demangle the function type from a given mangled symbol
+  /// without the return type and append it to the arguments, calling
+  /// convention and attribute output strings, respectively.
+  ///
+  /// \param Args output buffer to write the demangled arguments
+  /// \param Call output buffer to write the demangled calling convention
+  /// \param Attr output buffer to write the demangled attributes
+  /// \param Mangled mangled symbol to be demangled
+  ///
+  /// \return the remaining string on success or nullptr on failure
+  ///
+  /// \note Any of the output strings can be nullptr to throw the information
+  ///       away.
+  ///
+  /// \see https://dlang.org/spec/abi.html#TypeFunctionNoReturn
+  const char *parseFunctionTypeNoreturn(OutputString *Args, OutputString *Call,
+                                        OutputString *Attr,
+                                        const char *Mangled);
+
+  /// Extract and demangle the function type from a given mangled symbol
+  /// append it to the output string
+  ///
+  /// \param Decl output buffer to write the demangled name
+  /// \param Mangled mangled symbol to be demangled
+  ///
+  /// \return the remaining string on success or nullptr on failure
+  ///
+  /// \see https://dlang.org/spec/abi.html#TypeFunction
+  const char *parseFunctionType(OutputString *Decl, const char *Mangled);
+
+  /// Extract and demangle the function arguments list from a given mangled
+  /// symbol append it to the output string
+  ///
+  /// \param Decl output buffer to write the demangled name
+  /// \param Mangled mangled symbol to be demangled
+  ///
+  /// \return the remaining string on success or nullptr on failure
+  ///
+  /// \see https://dlang.org/spec/abi.html#Parameters
+  const char *parseFunctionArgs(OutputString *Decl, const char *Mangled);
+
   /// Extract and demangle a type from a given mangled symbol append it to
   /// the output string
   ///
@@ -508,6 +572,181 @@
   return std::isdigit(Qref[-Ret]);
 }
 
+const char *Demangler::parseCallConvention(OutputString *Decl,
+                                           const char *Mangled) {
+  if (Mangled == nullptr || *Mangled == '\0')
+    return nullptr;
+
+  switch (*Mangled) {
+  case 'F': /* (D) */
+    Mangled++;
+    break;
+
+  case 'U': /* (C) */
+    Mangled++;
+    Decl->append("extern(C) ");
+    break;
+
+  case 'W': /* (Windows) */
+    Mangled++;
+    Decl->append("extern(Windows) ");
+    break;
+
+  case 'V': /* (Pascal) */
+    Mangled++;
+    Decl->append("extern(Pascal) ");
+    break;
+
+  case 'R': /* (C++) */
+    Mangled++;
+    Decl->append("extern(C++) ");
+    break;
+
+  case 'Y': /* (Objective-C) */
+    Mangled++;
+    Decl->append("extern(Objective-C) ");
+    break;
+
+  default:
+    return nullptr;
+  }
+
+  return Mangled;
+}
+
+const char *Demangler::parseAttributes(OutputString *Decl,
+                                       const char *Mangled) {
+  if (Mangled == nullptr || *Mangled == '\0')
+    return nullptr;
+
+  while (*Mangled == 'N') {
+    Mangled++;
+    switch (*Mangled) {
+    case 'a': /* pure */
+      Mangled++;
+      Decl->append("pure ");
+      continue;
+
+    case 'b': /* nothrow */
+      Mangled++;
+      Decl->append("nothrow ");
+      continue;
+
+    case 'c': /* ref */
+      Mangled++;
+      Decl->append("ref ");
+      continue;
+
+    case 'd': /* @property */
+      Mangled++;
+      Decl->append("@property ");
+      continue;
+
+    case 'e': /* @trusted */
+      Mangled++;
+      Decl->append("@trusted ");
+      continue;
+
+    case 'f': /* @safe */
+      Mangled++;
+      Decl->append("@safe ");
+      continue;
+
+    case 'g':
+    case 'h':
+    case 'k':
+    case 'n':
+      /* inout parameter is represented as 'Ng'.
+         vector parameter is represented as 'Nh'.
+         return parameter is represented as 'Nk'.
+         typeof(*null) parameter is represented as 'Nn'.
+         If we see this, then we know we're really in the
+         parameter list.  Rewind and break.  */
+      Mangled--;
+      break;
+
+    case 'i': /* @nogc */
+      Mangled++;
+      Decl->append("@nogc ");
+      continue;
+
+    case 'j': /* return */
+      Mangled++;
+      Decl->append("return ");
+      continue;
+
+    case 'l': /* scope */
+      Mangled++;
+      Decl->append("scope ");
+      continue;
+
+    case 'm': /* @live */
+      Mangled++;
+      Decl->append("@live ");
+      continue;
+
+    default: /* unknown attribute */
+      return nullptr;
+    }
+    break;
+  }
+
+  return Mangled;
+}
+
+const char *Demangler::parseFunctionTypeNoreturn(OutputString *Args,
+                                                 OutputString *Call,
+                                                 OutputString *Attr,
+                                                 const char *Mangled) {
+  OutputString Dump = OutputString();
+  // Skip over calling convention and attributes
+  Mangled = parseCallConvention(Call ? Call : &Dump, Mangled);
+  Mangled = parseAttributes(Attr ? Attr : &Dump, Mangled);
+
+  if (Args)
+    Args->append("(");
+
+  Mangled = parseFunctionArgs(Args ? Args : &Dump, Mangled);
+  if (Args)
+    Args->append(")");
+
+  Dump.free();
+  return Mangled;
+}
+
+const char *Demangler::parseFunctionType(OutputString *Decl,
+                                         const char *Mangled) {
+  OutputString Attr, Args, Type;
+
+  if (Mangled == nullptr || *Mangled == '\0')
+    return nullptr;
+
+  /* The order of the mangled string is:
+        CallConvention FuncAttrs Arguments ArgClose Type
+     The demangled string is re-ordered as:
+        CallConvention Type Arguments FuncAttrs
+   */
+  Attr = OutputString();
+  Args = OutputString();
+  Type = OutputString();
+
+  Mangled = parseFunctionTypeNoreturn(&Args, Decl, &Attr, Mangled);
+
+  // Function return type
+  Mangled = parseType(&Type, Mangled);
+
+  // Append to decl in order
+  Decl->append(Type.Buffer, Type.getLength());
+  Decl->append(Args.Buffer, Args.getLength());
+  Decl->append(" ");
+  Decl->append(Attr.Buffer, Attr.getLength());
+
+  Attr.free();
+  Args.free();
+  Type.free();
+  return Mangled;
+}
+
 const char *Demangler::parseMangle(OutputString *Decl, const char *Mangled) {
   /* A D mangled symbol is comprised of both scope and type information.
         MangleName:
@@ -623,6 +862,71 @@
   return parseLName(Decl, Mangled, Len);
 }
 
+const char *Demangler::parseFunctionArgs(OutputString *Decl,
+                                         const char *Mangled) {
+  size_t N = 0;
+
+  while (Mangled && *Mangled != '\0') {
+    switch (*Mangled) {
+    case 'X': /* (variadic T t...) style */
+      Mangled++;
+      Decl->append("...");
+      return Mangled;
+    case 'Y': /* (variadic T t, ...) style */
+      Mangled++;
+      if (N != 0)
+        Decl->append(", ");
+      Decl->append("...");
+      return Mangled;
+    case 'Z': /* Normal function */
+      Mangled++;
+      return Mangled;
+    }
+
+    if (N++)
+      Decl->append(", ");
+
+    if (*Mangled == 'M') /* scope(T) */
+    {
+      Mangled++;
+      Decl->append("scope ");
+    }
+
+    if (Mangled[0] == 'N' && Mangled[1] == 'k') /* return(T) */
+    {
+      Mangled += 2;
+      Decl->append("return ");
+    }
+
+    switch (*Mangled) {
+    case 'I': /* in(T) */
+      Mangled++;
+      Decl->append("in ");
+      if (*Mangled == 'K') /* in ref(T) */
+      {
+        Mangled++;
+        Decl->append("ref ");
+      }
+      break;
+    case 'J': /* out(T) */
+      Mangled++;
+      Decl->append("out ");
+      break;
+    case 'K': /* ref(T) */
+      Mangled++;
+      Decl->append("ref ");
+      break;
+    case 'L': /* lazy(T) */
+      Mangled++;
+      Decl->append("lazy ");
+      break;
+    }
+    Mangled = parseType(Decl, Mangled);
+  }
+
+  return Mangled;
+}
+
 const char *Demangler::parseType(OutputString *Decl, const char *Mangled) {
   if (Mangled == nullptr || *Mangled == '\0')
     return nullptr;
@@ -726,7 +1030,17 @@
       return Mangled;
     }
 
-  // TODO: Parse function types
+  [[clang::fallthrough]];
+  case 'F': /* function T (D) */
+  case 'U': /* function T (C) */
+  case 'W': /* function T (Windows) */
+  case 'V': /* function T (Pascal) */
+  case 'R': /* function T (C++) */
+  case 'Y': /* function T (Objective-C) */
+    /* Function pointer types don't include the trailing asterisk.  */
+    Mangled = parseFunctionType(Decl, Mangled);
+    Decl->append("function");
+    return Mangled;
 
   [[clang::fallthrough]];
   case 'C': /* class T */
Index: llvm/unittests/Demangle/DLangDemangleTest.cpp
===================================================================
--- llvm/unittests/Demangle/DLangDemangleTest.cpp
+++ llvm/unittests/Demangle/DLangDemangleTest.cpp
@@ -42,7 +42,8 @@
       {"_D8demangle3ABCQeQg1ai", "demangle.ABC.ABC.ABC.a"},
       {"_D8demangle3ABCQeQaaaa1ai", nullptr},
       {"_D8demangle4ABCiQfQh1aQh", "demangle.ABCi.ABCi.ABCi.a"},
-      {"_D8demangle4ABCiQfQh1aQaaa", nullptr}
+      {"_D8demangle4ABCiQfQh1aQaaa", nullptr},
+      {"_D8demangle4testPFLAiYi", "demangle.test"}
   };
 
   for (ExpectedVal Val : ExpectedArray) {