c++: Implement __is_reference built-in trait

This patch implements built-in trait for std::is_reference.

gcc/cp/ChangeLog:

	* cp-trait.def: Define __is_reference.
	* constraint.cc (diagnose_trait_expr): Handle CPTK_IS_REFERENCE.
	* semantics.cc (trait_expr_value): Likewise.
	(finish_trait_expr): Likewise.

gcc/testsuite/ChangeLog:

	* g++.dg/ext/has-builtin-1.C: Test existence of __is_reference.
	* g++.dg/ext/is_reference.C: New test.

Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>

5 files changed, 45 insertions, 0 deletions

diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 204b998..aa42017 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -3789,6 +3789,9 @@ diagnose_trait_expr (tree expr, tree args)
     case CPTK_IS_POLYMORPHIC:
       inform (loc, "  %qT is not a polymorphic type", t1);
       break;
+    case CPTK_IS_REFERENCE:
+      inform (loc, "  %qT is not a reference", t1);
+      break;
     case CPTK_IS_SAME:
       inform (loc, "  %qT is not the same as %qT", t1, t2);
       break;
diff --git a/gcc/cp/cp-trait.def b/gcc/cp/cp-trait.def
index f5efffd..2d82ed3 100644
--- a/gcc/cp/cp-trait.def
+++ b/gcc/cp/cp-trait.def
@@ -80,6 +80,7 @@ DEFTRAIT_EXPR (IS_NOTHROW_CONVERTIBLE, "__is_nothrow_convertible", 2)
 DEFTRAIT_EXPR (IS_POINTER_INTERCONVERTIBLE_BASE_OF, "__is_pointer_interconvertible_base_of", 2)
 DEFTRAIT_EXPR (IS_POD, "__is_pod", 1)
 DEFTRAIT_EXPR (IS_POLYMORPHIC, "__is_polymorphic", 1)
+DEFTRAIT_EXPR (IS_REFERENCE, "__is_reference", 1)
 DEFTRAIT_EXPR (IS_SAME, "__is_same", 2)
 DEFTRAIT_EXPR (IS_SCOPED_ENUM, "__is_scoped_enum", 1)
 DEFTRAIT_EXPR (IS_STD_LAYOUT, "__is_standard_layout", 1)
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 5478c4b..4af5a60 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -12452,6 +12452,9 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2)
     case CPTK_IS_POLYMORPHIC:
       return CLASS_TYPE_P (type1) && TYPE_POLYMORPHIC_P (type1);
 
+    case CPTK_IS_REFERENCE:
+      return type_code1 == REFERENCE_TYPE;
+
     case CPTK_IS_SAME:
       return same_type_p (type1, type2);
 
@@ -12639,6 +12642,7 @@ finish_trait_expr (location_t loc, cp_trait_kind kind, tree type1, tree type2)
     case CPTK_IS_MEMBER_FUNCTION_POINTER:
     case CPTK_IS_MEMBER_OBJECT_POINTER:
     case CPTK_IS_MEMBER_POINTER:
+    case CPTK_IS_REFERENCE:
     case CPTK_IS_SAME:
     case CPTK_IS_SCOPED_ENUM:
     case CPTK_IS_UNION:
diff --git a/gcc/testsuite/g++.dg/ext/has-builtin-1.C b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
index b579707..b667b5c 100644
--- a/gcc/testsuite/g++.dg/ext/has-builtin-1.C
+++ b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
@@ -119,6 +119,9 @@
 #if !__has_builtin (__is_polymorphic)
 # error "__has_builtin (__is_polymorphic) failed"
 #endif
+#if !__has_builtin (__is_reference)
+# error "__has_builtin (__is_reference) failed"
+#endif
 #if !__has_builtin (__is_same)
 # error "__has_builtin (__is_same) failed"
 #endif
diff --git a/gcc/testsuite/g++.dg/ext/is_reference.C b/gcc/testsuite/g++.dg/ext/is_reference.C
new file mode 100644
index 0000000..b5ce4db
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/is_reference.C
@@ -0,0 +1,34 @@
+// { dg-do compile { target c++11 } }
+
+#include <testsuite_tr1.h>
+
+using namespace __gnu_test;
+
+#define SA(X) static_assert((X),#X)
+#define SA_TEST_CATEGORY(TRAIT, TYPE, EXPECT)	\
+  SA(TRAIT(TYPE) == EXPECT);					\
+  SA(TRAIT(const TYPE) == EXPECT);				\
+  SA(TRAIT(volatile TYPE) == EXPECT);			\
+  SA(TRAIT(const volatile TYPE) == EXPECT)
+
+// Positive tests.
+SA_TEST_CATEGORY(__is_reference, int&, true);
+SA_TEST_CATEGORY(__is_reference, ClassType&, true);
+SA(__is_reference(int(&)(int)));
+SA_TEST_CATEGORY(__is_reference, int&&, true);
+SA_TEST_CATEGORY(__is_reference, ClassType&&, true);
+SA(__is_reference(int(&&)(int)));
+SA_TEST_CATEGORY(__is_reference, IncompleteClass&, true);
+
+// Negative tests
+SA_TEST_CATEGORY(__is_reference, void, false);
+SA_TEST_CATEGORY(__is_reference, int*, false);
+SA_TEST_CATEGORY(__is_reference, int[3], false);
+SA(!__is_reference(int(int)));
+SA(!__is_reference(int(*const)(int)));
+SA(!__is_reference(int(*volatile)(int)));
+SA(!__is_reference(int(*const volatile)(int)));
+
+// Sanity check.
+SA_TEST_CATEGORY(__is_reference, ClassType, false);
+SA_TEST_CATEGORY(__is_reference, IncompleteClass, false);