diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -3493,7 +3493,7 @@
 def CFGuard : InheritableAttr {
   // Currently only the __declspec(guard(nocf)) modifier is supported. In future
   // we might also want to support __declspec(guard(suppress)).
-  let Spellings = [Declspec<"guard">];
+  let Spellings = [Declspec<"guard">, GCC<"guard">];
   let Subjects = SubjectList<[Function]>;
   let Args = [EnumArgument<"Guard", "GuardArg", ["nocf"], ["nocf"]>];
   let Documentation = [CFGuardDocs];
diff --git a/clang/test/CodeGen/guard_nocf.c b/clang/test/CodeGen/guard_nocf.c
--- a/clang/test/CodeGen/guard_nocf.c
+++ b/clang/test/CodeGen/guard_nocf.c
@@ -1,4 +1,8 @@
 // RUN: %clang_cc1 -triple %ms_abi_triple -fms-extensions -emit-llvm -O2 -o - %s | FileCheck %s
+// RUN: %clang_cc1 -triple %itanium_abi_triple -emit-llvm -O2 -o - %s | FileCheck %s
+
+// The %itanium_abi_triple version tests mingw target, which relies on
+// __declspec(...) being defined as __attribute__((...)) by compiler built-in.
 
 void target_func(void);
 void (*func_ptr)(void) = &target_func;
diff --git a/clang/test/CodeGenCXX/guard_nocf.cpp b/clang/test/CodeGenCXX/guard_nocf.cpp
--- a/clang/test/CodeGenCXX/guard_nocf.cpp
+++ b/clang/test/CodeGenCXX/guard_nocf.cpp
@@ -1,4 +1,8 @@
 // RUN: %clang_cc1 -triple %ms_abi_triple -fms-extensions -std=c++11 -emit-llvm -O2 -o - %s | FileCheck %s
+// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++11 -emit-llvm -O2 -o - %s | FileCheck %s
+
+// The %itanium_abi_triple version tests mingw target, which relies on
+// __declspec(...) being defined as __attribute__((...)) by compiler built-in.
 
 void target_func();
 void (*func_ptr)() = &target_func;
diff --git a/clang/test/Misc/pragma-attribute-supported-attributes-list.test b/clang/test/Misc/pragma-attribute-supported-attributes-list.test
--- a/clang/test/Misc/pragma-attribute-supported-attributes-list.test
+++ b/clang/test/Misc/pragma-attribute-supported-attributes-list.test
@@ -26,6 +26,7 @@
 // CHECK-NEXT: BuiltinAlias (SubjectMatchRule_function)
 // CHECK-NEXT: CFAuditedTransfer (SubjectMatchRule_function)
 // CHECK-NEXT: CFConsumed (SubjectMatchRule_variable_is_parameter)
+// CHECK-NEXT: CFGuard (SubjectMatchRule_function)
 // CHECK-NEXT: CFICanonicalJumpTable (SubjectMatchRule_function)
 // CHECK-NEXT: CFUnknownTransfer (SubjectMatchRule_function)
 // CHECK-NEXT: CPUDispatch (SubjectMatchRule_function)
diff --git a/clang/test/Sema/attr-guard_nocf.c b/clang/test/Sema/attr-guard_nocf.c
--- a/clang/test/Sema/attr-guard_nocf.c
+++ b/clang/test/Sema/attr-guard_nocf.c
@@ -1,5 +1,10 @@
 // RUN: %clang_cc1 -triple %ms_abi_triple -fms-extensions -verify -fsyntax-only %s
 // RUN: %clang_cc1 -triple %ms_abi_triple -fms-extensions -verify -std=c++11 -fsyntax-only -x c++ %s
+// RUN: %clang_cc1 -triple %itanium_abi_triple -verify -fsyntax-only %s
+// RUN: %clang_cc1 -triple %itanium_abi_triple -verify -std=c++11 -fsyntax-only -x c++ %s
+
+// The %itanium_abi_triple version tests mingw target, which relies on
+// __declspec(...) being defined as __attribute__((...)) by compiler built-in.
 
 // Function definition.
 __declspec(guard(nocf)) void testGuardNoCF(void) { // no warning
diff --git a/llvm/test/CodeGen/AArch64/cfguard-checks.ll b/llvm/test/CodeGen/AArch64/cfguard-checks.ll
--- a/llvm/test/CodeGen/AArch64/cfguard-checks.ll
+++ b/llvm/test/CodeGen/AArch64/cfguard-checks.ll
@@ -1,4 +1,5 @@
 ; RUN: llc < %s -mtriple=aarch64-pc-windows-msvc | FileCheck %s
+; RUN: llc < %s -mtriple=aarch64-pc-windows-gnu | FileCheck %s
 ; Control Flow Guard is currently only available on Windows
 
 ; Test that Control Flow Guard checks are correctly added when required.
diff --git a/llvm/test/CodeGen/ARM/cfguard-checks.ll b/llvm/test/CodeGen/ARM/cfguard-checks.ll
--- a/llvm/test/CodeGen/ARM/cfguard-checks.ll
+++ b/llvm/test/CodeGen/ARM/cfguard-checks.ll
@@ -1,4 +1,5 @@
 ; RUN: llc < %s -mtriple=arm-pc-windows-msvc | FileCheck %s
+; RUN: llc < %s -mtriple=arm-pc-windows-gnu | FileCheck %s
 ; Control Flow Guard is currently only available on Windows
 
 ; Test that Control Flow Guard checks are correctly added when required.
diff --git a/llvm/test/CodeGen/X86/cfguard-checks.ll b/llvm/test/CodeGen/X86/cfguard-checks.ll
--- a/llvm/test/CodeGen/X86/cfguard-checks.ll
+++ b/llvm/test/CodeGen/X86/cfguard-checks.ll
@@ -1,5 +1,7 @@
 ; RUN: llc < %s -mtriple=i686-pc-windows-msvc | FileCheck %s -check-prefix=X32
 ; RUN: llc < %s -mtriple=x86_64-pc-windows-msvc | FileCheck %s -check-prefix=X64
+; RUN: llc < %s -mtriple=i686-pc-windows-gnu | FileCheck %s -check-prefix=X32
+; RUN: llc < %s -mtriple=x86_64-pc-windows-gnu | FileCheck %s -check-prefix=X64
 ; Control Flow Guard is currently only available on Windows
 
 ; Test that Control Flow Guard checks are correctly added when required.