Index: include/clang/Basic/Attr.td
===================================================================
--- include/clang/Basic/Attr.td
+++ include/clang/Basic/Attr.td
@@ -484,6 +484,11 @@
   bit InheritEvenIfAlreadyPresent = 0;
 }
 
+/// Some attributes, like calling conventions, can appear in either the
+/// declaration or the type position. These attributes are morally type
+/// attributes, but have historically been written on declarations.
+class DeclOrTypeAttr : InheritableAttr;
+
 /// A target-specific attribute.  This class is meant to be used as a mixin
 /// with InheritableAttr or Attr depending on the attribute's needs.
 class TargetSpecificAttr<TargetSpec target> {
@@ -750,7 +755,7 @@
   let Documentation = [CarriesDependencyDocs];
 }
 
-def CDecl : InheritableAttr {
+def CDecl : DeclOrTypeAttr {
   let Spellings = [GCC<"cdecl">, Keyword<"__cdecl">, Keyword<"_cdecl">];
 //  let Subjects = [Function, ObjCMethod];
   let Documentation = [Undocumented];
@@ -1050,14 +1055,14 @@
   let Documentation = [FallthroughDocs];
 }
 
-def FastCall : InheritableAttr {
+def FastCall : DeclOrTypeAttr {
   let Spellings = [GCC<"fastcall">, Keyword<"__fastcall">,
                    Keyword<"_fastcall">];
 //  let Subjects = [Function, ObjCMethod];
   let Documentation = [FastCallDocs];
 }
 
-def RegCall : InheritableAttr {
+def RegCall : DeclOrTypeAttr {
   let Spellings = [GCC<"regcall">, Keyword<"__regcall">];
   let Documentation = [RegCallDocs];
 }
@@ -1189,7 +1194,7 @@
   let Documentation = [Undocumented];
 }
 
-def MSABI : InheritableAttr {
+def MSABI : DeclOrTypeAttr {
   let Spellings = [GCC<"ms_abi">];
 //  let Subjects = [Function, ObjCMethod];
   let Documentation = [MSABIDocs];
@@ -1672,13 +1677,13 @@
   let Documentation = [Undocumented];
 }
 
-def IntelOclBicc : InheritableAttr {
+def IntelOclBicc : DeclOrTypeAttr {
   let Spellings = [Clang<"intel_ocl_bicc", 0>];
 //  let Subjects = [Function, ObjCMethod];
   let Documentation = [Undocumented];
 }
 
-def Pcs : InheritableAttr {
+def Pcs : DeclOrTypeAttr {
   let Spellings = [GCC<"pcs">];
   let Args = [EnumArgument<"PCS", "PCSType",
                            ["aapcs", "aapcs-vfp"],
@@ -1781,13 +1786,13 @@
   let Documentation = [Undocumented];
 }
 
-def StdCall : InheritableAttr {
+def StdCall : DeclOrTypeAttr {
   let Spellings = [GCC<"stdcall">, Keyword<"__stdcall">, Keyword<"_stdcall">];
 //  let Subjects = [Function, ObjCMethod];
   let Documentation = [StdCallDocs];
 }
 
-def SwiftCall : InheritableAttr {
+def SwiftCall : DeclOrTypeAttr {
   let Spellings = [Clang<"swiftcall">];
 //  let Subjects = SubjectList<[Function]>;
   let Documentation = [SwiftCallDocs];
@@ -1814,38 +1819,38 @@
   let Documentation = [SuppressDocs];
 }
 
-def SysVABI : InheritableAttr {
+def SysVABI : DeclOrTypeAttr {
   let Spellings = [GCC<"sysv_abi">];
 //  let Subjects = [Function, ObjCMethod];
   let Documentation = [Undocumented];
 }
 
-def ThisCall : InheritableAttr {
+def ThisCall : DeclOrTypeAttr {
   let Spellings = [GCC<"thiscall">, Keyword<"__thiscall">,
                    Keyword<"_thiscall">];
 //  let Subjects = [Function, ObjCMethod];
   let Documentation = [ThisCallDocs];
 }
 
-def VectorCall : InheritableAttr {
+def VectorCall : DeclOrTypeAttr {
   let Spellings = [Clang<"vectorcall">, Keyword<"__vectorcall">,
                    Keyword<"_vectorcall">];
 //  let Subjects = [Function, ObjCMethod];
   let Documentation = [VectorCallDocs];
 }
 
-def Pascal : InheritableAttr {
+def Pascal : DeclOrTypeAttr {
   let Spellings = [Clang<"pascal">, Keyword<"__pascal">, Keyword<"_pascal">];
 //  let Subjects = [Function, ObjCMethod];
   let Documentation = [Undocumented];
 }
 
-def PreserveMost : InheritableAttr {
+def PreserveMost : DeclOrTypeAttr {
   let Spellings = [Clang<"preserve_most">];
   let Documentation = [PreserveMostDocs];
 }
 
-def PreserveAll : InheritableAttr {
+def PreserveAll : DeclOrTypeAttr {
   let Spellings = [Clang<"preserve_all">];
   let Documentation = [PreserveAllDocs];
 }
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -3310,6 +3310,9 @@
   "%0 attribute is not supported in %select{C|C++|Objective-C}1">;
 def err_attribute_not_supported_on_arch
     : Error<"%0 attribute is not supported on '%1'">;
+def warn_gcc_ignores_type_attr : Warning<
+  "GCC does not allow the %0 attribute to be written on a type">,
+  InGroup<GccCompat>;
 
 // Clang-Specific Attributes
 def warn_attribute_iboutlet : Warning<
Index: lib/Sema/SemaType.cpp
===================================================================
--- lib/Sema/SemaType.cpp
+++ lib/Sema/SemaType.cpp
@@ -7142,14 +7142,19 @@
 
     if (attr.isCXX11Attribute()) {
       // [[gnu::...]] attributes are treated as declaration attributes, so may
-      // not appertain to a DeclaratorChunk, even if we handle them as type
-      // attributes.
+      // not appertain to a DeclaratorChunk. If we handle them as type
+      // attributes, accept them in that position and diagnose the GCC
+      // incompatibility.
       if (attr.getScopeName() && attr.getScopeName()->isStr("gnu")) {
+        bool IsTypeAttr = attr.isTypeAttr();
         if (TAL == TAL_DeclChunk) {
           state.getSema().Diag(attr.getLoc(),
-                               diag::warn_cxx11_gnu_attribute_on_type)
+                               IsTypeAttr
+                                   ? diag::warn_gcc_ignores_type_attr
+                                   : diag::warn_cxx11_gnu_attribute_on_type)
               << attr.getName();
-          continue;
+          if (!IsTypeAttr)
+            continue;
         }
       } else if (TAL != TAL_DeclChunk) {
         // Otherwise, only consider type processing for a C++11 attribute if
Index: test/SemaCXX/cxx11-gnu-attrs.cpp
===================================================================
--- test/SemaCXX/cxx11-gnu-attrs.cpp
+++ test/SemaCXX/cxx11-gnu-attrs.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -triple x86_64-unknown-unknown -std=c++11 -verify %s
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -std=c++11 -Wno-gcc-compat -verify %s
 
 // Error cases.
 
@@ -18,8 +18,7 @@
 // expected-warning@-2 {{calling convention '__stdcall' ignored for this target}}
 [[gnu::fastcall]] void pr17424_4() [[gnu::stdcall]];
 // expected-warning@-1 {{calling convention 'fastcall' ignored for this target}}
-// expected-warning@-2 {{attribute 'stdcall' ignored, because it cannot be applied to a type}}
-// expected-warning@-3 {{calling convention 'stdcall' ignored for this target}}
+// expected-warning@-2 {{calling convention 'stdcall' ignored for this target}}
 void pr17424_5 [[gnu::fastcall]]();
 // expected-warning@-1 {{calling convention 'fastcall' ignored for this target}}
 
Index: test/SemaCXX/type-attrs.cpp
===================================================================
--- test/SemaCXX/type-attrs.cpp
+++ test/SemaCXX/type-attrs.cpp
@@ -0,0 +1,5 @@
+// RUN: %clang_cc1 -triple x86_64-pc-win32 -Wgcc-compat -std=c++11 -verify %s
+
+void f() [[gnu::cdecl]] {}  // expected-warning {{GCC does not allow the 'cdecl' attribute to be written on a type}}
+void g() [[gnu::stdcall]] {}  // expected-warning {{GCC does not allow the 'stdcall' attribute to be written on a type}}
+void i() [[gnu::fastcall]] {}  // expected-warning {{GCC does not allow the 'fastcall' attribute to be written on a type}}
Index: utils/TableGen/ClangAttrEmitter.cpp
===================================================================
--- utils/TableGen/ClangAttrEmitter.cpp
+++ utils/TableGen/ClangAttrEmitter.cpp
@@ -2068,7 +2068,8 @@
     bool Inheritable = false;
     for (const auto &Super : llvm::reverse(Supers)) {
       const Record *R = Super.first;
-      if (R->getName() != "TargetSpecificAttr" && SuperName.empty())
+      if (R->getName() != "TargetSpecificAttr" &&
+          R->getName() != "DeclOrTypeAttr" && SuperName.empty())
         SuperName = R->getName();
       if (R->getName() == "InheritableAttr")
         Inheritable = true;
@@ -3437,7 +3438,9 @@
     emitArgInfo(*I->second, SS);
     SS << ", " << I->second->getValueAsBit("HasCustomParsing");
     SS << ", " << I->second->isSubClassOf("TargetSpecificAttr");
-    SS << ", " << I->second->isSubClassOf("TypeAttr");
+    SS << ", "
+       << (I->second->isSubClassOf("TypeAttr") ||
+           I->second->isSubClassOf("DeclOrTypeAttr"));
     SS << ", " << I->second->isSubClassOf("StmtAttr");
     SS << ", " << IsKnownToGCC(*I->second);
     SS << ", " << PragmaAttributeSupport.isAttributedSupported(*I->second);