[PATCH 1/2] c++: implement __is_reference built-in trait

[PATCH 1/2] c++: implement __is_reference built-in trait

[Ken Matsui]

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.
---
 gcc/cp/constraint.cc                     |  3 +++
 gcc/cp/cp-trait.def                      |  1 +
 gcc/cp/semantics.cc                      |  4 ++++
 gcc/testsuite/g++.dg/ext/has-builtin-1.C |  3 +++
 gcc/testsuite/g++.dg/ext/is_reference.C  | 26 ++++++++++++++++++++++++
 5 files changed, 37 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/ext/is_reference.C

diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 273d15ab097..23e5bc24dbb 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -3701,6 +3701,9 @@ diagnose_trait_expr (tree expr, tree args)
     case CPTK_HAS_VIRTUAL_DESTRUCTOR:
       inform (loc, "  %qT does not have a virtual destructor", t1);
       break;
+    case CPTK_IS_REFERENCE:
+      inform (loc, "  %qT is not a reference", t1);
+      break;
     case CPTK_IS_ABSTRACT:
       inform (loc, "  %qT is not an abstract class", t1);
       break;
diff --git a/gcc/cp/cp-trait.def b/gcc/cp/cp-trait.def
index bac593c0094..63a64152ce6 100644
--- a/gcc/cp/cp-trait.def
+++ b/gcc/cp/cp-trait.def
@@ -67,6 +67,7 @@ DEFTRAIT_EXPR (IS_CONVERTIBLE, "__is_convertible", 2)
 DEFTRAIT_EXPR (IS_EMPTY, "__is_empty", 1)
 DEFTRAIT_EXPR (IS_ENUM, "__is_enum", 1)
 DEFTRAIT_EXPR (IS_FINAL, "__is_final", 1)
+DEFTRAIT_EXPR (IS_REFERENCE, "__is_reference", 1)
 DEFTRAIT_EXPR (IS_LAYOUT_COMPATIBLE, "__is_layout_compatible", 2)
 DEFTRAIT_EXPR (IS_LITERAL_TYPE, "__is_literal_type", 1)
 DEFTRAIT_EXPR (IS_NOTHROW_ASSIGNABLE, "__is_nothrow_assignable", 2)
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 87c2e8a7111..dce98af4f72 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -11995,6 +11995,9 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2)
     case CPTK_IS_FINAL:
       return CLASS_TYPE_P (type1) && CLASSTYPE_FINAL (type1);
 
+    case CPTK_IS_REFERENCE:
+      return type_code1 == REFERENCE_TYPE;
+
     case CPTK_IS_LAYOUT_COMPATIBLE:
       return layout_compatible_type_p (type1, type2);
 
@@ -12139,6 +12142,7 @@ finish_trait_expr (location_t loc, cp_trait_kind kind, tree type1, tree type2)
     case CPTK_HAS_TRIVIAL_COPY:
     case CPTK_HAS_TRIVIAL_DESTRUCTOR:
     case CPTK_HAS_UNIQUE_OBJ_REPRESENTATIONS:
+    case CPTK_IS_REFERENCE:
       if (!check_trait_type (type1))
 	return error_mark_node;
       break;
diff --git a/gcc/testsuite/g++.dg/ext/has-builtin-1.C b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
index f343e153e56..b697673790c 100644
--- a/gcc/testsuite/g++.dg/ext/has-builtin-1.C
+++ b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
@@ -146,3 +146,6 @@
 #if !__has_builtin (__remove_cvref)
 # error "__has_builtin (__remove_cvref) failed"
 #endif
+#if !__has_builtin (__is_reference)
+# error "__has_builtin (__is_reference) 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 00000000000..b4f048538e5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/is_reference.C
@@ -0,0 +1,26 @@
+// { dg-do compile { target c++11 } }
+
+#define SA(X) static_assert((X),#X)
+
+SA(!__is_reference(void));
+SA(!__is_reference(int*));
+
+SA(__is_reference(int&));
+SA(__is_reference(const int&));
+SA(__is_reference(volatile int&));
+SA(__is_reference(const volatile int&));
+
+SA(__is_reference(int&&));
+SA(__is_reference(const int&&));
+SA(__is_reference(volatile int&&));
+SA(__is_reference(const volatile int&&));
+
+SA(!__is_reference(int[3]));
+SA(!__is_reference(const int[3]));
+SA(!__is_reference(volatile int[3]));
+SA(!__is_reference(const volatile int[3]));
+
+SA(!__is_reference(int(int)));
+SA(!__is_reference(int(*const)(int)));
+SA(!__is_reference(int(*volatile)(int)));
+SA(!__is_reference(int(*const volatile)(int)));
-- 
2.40.0

[PATCH 2/2] libstdc++: use new built-in trait __is_reference

[Ken Matsui]

This patch lets libstdc++ use new built-in trait __is_reference.

libstdc++-v3/ChangeLog:

	* include/std/type_traits (is_reference): Use __is_reference built-in trait.
---
 libstdc++-v3/include/std/type_traits | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index 2bd607a8b8f..18408d8ceb6 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -639,6 +639,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   // Composite type categories.
 
   /// is_reference
+#if __has_builtin(__is_reference)
+  template<typename _Tp>
+    struct is_reference
+    : public integral_constant<bool, __is_reference(_Tp)>
+    { };
+#else
   template<typename _Tp>
     struct is_reference
     : public false_type
@@ -653,6 +659,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     struct is_reference<_Tp&&>
     : public true_type
     { };
+#endif
 
   /// is_arithmetic
   template<typename _Tp>
-- 
2.40.0