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

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

[Ken Matsui]

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

gcc/cp/ChangeLog:

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

gcc/testsuite/ChangeLog:

	* g++.dg/ext/has-builtin-1.C: Test existence of __is_array.
	* g++.dg/ext/is_array.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_array.C      | 28 ++++++++++++++++++++++++
 5 files changed, 39 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/ext/is_array.C

diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 273d15ab097..4fe167ac7ed 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -3747,6 +3747,9 @@ diagnose_trait_expr (tree expr, tree args)
     case CPTK_IS_UNION:
       inform (loc, "  %qT is not a union", t1);
       break;
+    case CPTK_IS_ARRAY:
+      inform (loc, "  %qT is not an array", t1);
+      break;
     case CPTK_IS_AGGREGATE:
       inform (loc, "  %qT is not an aggregate", t1);
       break;
diff --git a/gcc/cp/cp-trait.def b/gcc/cp/cp-trait.def
index bac593c0094..87b1ca75a2d 100644
--- a/gcc/cp/cp-trait.def
+++ b/gcc/cp/cp-trait.def
@@ -82,6 +82,7 @@ DEFTRAIT_EXPR (IS_TRIVIALLY_ASSIGNABLE, "__is_trivially_assignable", 2)
 DEFTRAIT_EXPR (IS_TRIVIALLY_CONSTRUCTIBLE, "__is_trivially_constructible", -1)
 DEFTRAIT_EXPR (IS_TRIVIALLY_COPYABLE, "__is_trivially_copyable", 1)
 DEFTRAIT_EXPR (IS_UNION, "__is_union", 1)
+DEFTRAIT_EXPR (IS_ARRAY, "__is_array", 1)
 DEFTRAIT_EXPR (REF_CONSTRUCTS_FROM_TEMPORARY, "__reference_constructs_from_temporary", 2)
 DEFTRAIT_EXPR (REF_CONVERTS_FROM_TEMPORARY, "__reference_converts_from_temporary", 2)
 /* FIXME Added space to avoid direct usage in GCC 13.  */
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 87c2e8a7111..9acf8f5877a 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -12031,6 +12031,9 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2)
     case CPTK_IS_UNION:
       return type_code1 == UNION_TYPE;
 
+    case CPTK_IS_ARRAY:
+      return type_code1 == ARRAY_TYPE;
+
     case CPTK_IS_ASSIGNABLE:
       return is_xible (MODIFY_EXPR, type1, type2);
 
@@ -12200,6 +12203,7 @@ finish_trait_expr (location_t loc, cp_trait_kind kind, tree type1, tree type2)
     case CPTK_IS_ENUM:
     case CPTK_IS_UNION:
     case CPTK_IS_SAME:
+    case CPTK_IS_ARRAY:
       break;
 
     case CPTK_IS_LAYOUT_COMPATIBLE:
diff --git a/gcc/testsuite/g++.dg/ext/has-builtin-1.C b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
index f343e153e56..56485ae62be 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_array)
+# error "__has_builtin (__is_array) failed"
+#endif
diff --git a/gcc/testsuite/g++.dg/ext/is_array.C b/gcc/testsuite/g++.dg/ext/is_array.C
new file mode 100644
index 00000000000..facfed5c7cb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/is_array.C
@@ -0,0 +1,28 @@
+// { 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, X, expect) \
+  SA(TRAIT(X) == expect);                  \
+  SA(TRAIT(const X) == expect);            \
+  SA(TRAIT(volatile X) == expect);         \
+  SA(TRAIT(const volatile X) == expect)
+
+SA_TEST_CATEGORY(__is_array, int[2], true);
+SA_TEST_CATEGORY(__is_array, int[], true);
+SA_TEST_CATEGORY(__is_array, int[2][3], true);
+SA_TEST_CATEGORY(__is_array, int[][3], true);
+SA_TEST_CATEGORY(__is_array, float*[2], true);
+SA_TEST_CATEGORY(__is_array, float*[], true);
+SA_TEST_CATEGORY(__is_array, float*[2][3], true);
+SA_TEST_CATEGORY(__is_array, float*[][3], true);
+SA_TEST_CATEGORY(__is_array, ClassType[2], true);
+SA_TEST_CATEGORY(__is_array, ClassType[], true);
+SA_TEST_CATEGORY(__is_array, ClassType[2][3], true);
+SA_TEST_CATEGORY(__is_array, ClassType[][3], true);
+
+// Sanity check.
+SA_TEST_CATEGORY(__is_array, ClassType, false);
-- 
2.40.0

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

[Ken Matsui]

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

libstdc++-v3/ChangeLog:

	* include/std/type_traits (is_array): Use __is_array 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..a9b1a6eb62a 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -503,6 +503,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     { };
 
   /// is_array
+#if __has_builtin(__is_array)
+  template<typename _Tp>
+    struct is_array
+    : public __bool_constant<__is_array(_Tp)>
+    { };
+#else
   template<typename>
     struct is_array
     : public false_type { };
@@ -514,6 +520,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _Tp>
     struct is_array<_Tp[]>
     : public true_type { };
+#endif
 
   template<typename>
     struct __is_pointer_helper
-- 
2.40.0

[PATCH v2 1/2] c++: implement __is_array built-in trait

[Ken Matsui]

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

gcc/cp/ChangeLog:

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

gcc/testsuite/ChangeLog:

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

Signed-off-by: Ken Matsui <kmatsui@cs.washington.edu>
---
 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_array.C      | 28 ++++++++++++++++++++++++
 5 files changed, 39 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/ext/is_array.C

diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 8cf0f2d0974..7cec7eba591 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -3751,6 +3751,9 @@ diagnose_trait_expr (tree expr, tree args)
     case CPTK_IS_UNION:
       inform (loc, "  %qT is not a union", t1);
       break;
+    case CPTK_IS_ARRAY:
+      inform (loc, "  %qT is not an array", t1);
+      break;
     case CPTK_IS_AGGREGATE:
       inform (loc, "  %qT is not an aggregate", t1);
       break;
diff --git a/gcc/cp/cp-trait.def b/gcc/cp/cp-trait.def
index 8b7fece0cc8..f68c7f2e8ec 100644
--- a/gcc/cp/cp-trait.def
+++ b/gcc/cp/cp-trait.def
@@ -82,6 +82,7 @@ DEFTRAIT_EXPR (IS_TRIVIALLY_ASSIGNABLE, "__is_trivially_assignable", 2)
 DEFTRAIT_EXPR (IS_TRIVIALLY_CONSTRUCTIBLE, "__is_trivially_constructible", -1)
 DEFTRAIT_EXPR (IS_TRIVIALLY_COPYABLE, "__is_trivially_copyable", 1)
 DEFTRAIT_EXPR (IS_UNION, "__is_union", 1)
+DEFTRAIT_EXPR (IS_ARRAY, "__is_array", 1)
 DEFTRAIT_EXPR (REF_CONSTRUCTS_FROM_TEMPORARY, "__reference_constructs_from_temporary", 2)
 DEFTRAIT_EXPR (REF_CONVERTS_FROM_TEMPORARY, "__reference_converts_from_temporary", 2)
 /* FIXME Added space to avoid direct usage in GCC 13.  */
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 8fb47fd179e..22f2700ec0b 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -12118,6 +12118,9 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2)
     case CPTK_IS_UNION:
       return type_code1 == UNION_TYPE;
 
+    case CPTK_IS_ARRAY:
+      return type_code1 == ARRAY_TYPE;
+
     case CPTK_IS_ASSIGNABLE:
       return is_xible (MODIFY_EXPR, type1, type2);
 
@@ -12296,6 +12299,7 @@ finish_trait_expr (location_t loc, cp_trait_kind kind, tree type1, tree type2)
     case CPTK_IS_ENUM:
     case CPTK_IS_UNION:
     case CPTK_IS_SAME:
+    case CPTK_IS_ARRAY:
       break;
 
     case CPTK_IS_LAYOUT_COMPATIBLE:
diff --git a/gcc/testsuite/g++.dg/ext/has-builtin-1.C b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
index f343e153e56..56485ae62be 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_array)
+# error "__has_builtin (__is_array) failed"
+#endif
diff --git a/gcc/testsuite/g++.dg/ext/is_array.C b/gcc/testsuite/g++.dg/ext/is_array.C
new file mode 100644
index 00000000000..facfed5c7cb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/is_array.C
@@ -0,0 +1,28 @@
+// { 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, X, expect) \
+  SA(TRAIT(X) == expect);                  \
+  SA(TRAIT(const X) == expect);            \
+  SA(TRAIT(volatile X) == expect);         \
+  SA(TRAIT(const volatile X) == expect)
+
+SA_TEST_CATEGORY(__is_array, int[2], true);
+SA_TEST_CATEGORY(__is_array, int[], true);
+SA_TEST_CATEGORY(__is_array, int[2][3], true);
+SA_TEST_CATEGORY(__is_array, int[][3], true);
+SA_TEST_CATEGORY(__is_array, float*[2], true);
+SA_TEST_CATEGORY(__is_array, float*[], true);
+SA_TEST_CATEGORY(__is_array, float*[2][3], true);
+SA_TEST_CATEGORY(__is_array, float*[][3], true);
+SA_TEST_CATEGORY(__is_array, ClassType[2], true);
+SA_TEST_CATEGORY(__is_array, ClassType[], true);
+SA_TEST_CATEGORY(__is_array, ClassType[2][3], true);
+SA_TEST_CATEGORY(__is_array, ClassType[][3], true);
+
+// Sanity check.
+SA_TEST_CATEGORY(__is_array, ClassType, false);
-- 
2.41.0

[PATCH v2 2/2] libstdc++: use new built-in trait __is_array

[Ken Matsui]

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

libstdc++-v3/ChangeLog:

	* include/std/type_traits (is_array): Use __is_array built-in trait.
	(is_array_v): Likewise.

Signed-off-by: Ken Matsui <kmatsui@cs.washington.edu>
---
 libstdc++-v3/include/std/type_traits | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index 0e7a9c9c7f3..f2a3a327e7d 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -503,6 +503,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     { };
 
   /// is_array
+#if __has_builtin(__is_array)
+  template<typename _Tp>
+    struct is_array
+    : public __bool_constant<__is_array(_Tp)>
+    { };
+#else
   template<typename>
     struct is_array
     : public false_type { };
@@ -514,6 +520,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _Tp>
     struct is_array<_Tp[]>
     : public true_type { };
+#endif
 
   template<typename>
     struct __is_pointer_helper
@@ -3161,12 +3168,17 @@ template <typename _Tp>
 template <typename _Tp>
   inline constexpr bool is_floating_point_v = is_floating_point<_Tp>::value;
 
+#if __has_builtin(__is_array)
+template <typename _Tp>
+  inline constexpr bool is_array_v = __is_array(_Tp);
+#else
 template <typename _Tp>
   inline constexpr bool is_array_v = false;
 template <typename _Tp>
   inline constexpr bool is_array_v<_Tp[]> = true;
 template <typename _Tp, size_t _Num>
   inline constexpr bool is_array_v<_Tp[_Num]> = true;
+#endif
 
 template <typename _Tp>
   inline constexpr bool is_pointer_v = is_pointer<_Tp>::value;
-- 
2.41.0

Re: [PATCH v2 1/2] c++: implement __is_array built-in trait

[Ken Matsui]

Here is the benchmark result for is_array:

https://github.com/ken-matsui/gcc-benches/blob/main/is_array.md#sat-jun-24-070630-am-pdt-2023

Time: -15.511%
Peak Memory Usage: +0.173923%
Total Memory Usage: -6.2037%

On Sat, Jun 24, 2023 at 6:54 AM Ken Matsui <kmatsui@cs.washington.edu> wrote:
>
> This patch implements built-in trait for std::is_array.
>
> gcc/cp/ChangeLog:
>
>         * cp-trait.def: Define __is_array.
>         * constraint.cc (diagnose_trait_expr): Handle CPTK_IS_ARRAY.
>         * semantics.cc (trait_expr_value): Likewise.
>         (finish_trait_expr): Likewise.
>
> gcc/testsuite/ChangeLog:
>
>         * g++.dg/ext/has-builtin-1.C: Test existence of __is_array.
>         * g++.dg/ext/is_array.C: New test.
>
> Signed-off-by: Ken Matsui <kmatsui@cs.washington.edu>
> ---
>  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_array.C      | 28 ++++++++++++++++++++++++
>  5 files changed, 39 insertions(+)
>  create mode 100644 gcc/testsuite/g++.dg/ext/is_array.C
>
> diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
> index 8cf0f2d0974..7cec7eba591 100644
> --- a/gcc/cp/constraint.cc
> +++ b/gcc/cp/constraint.cc
> @@ -3751,6 +3751,9 @@ diagnose_trait_expr (tree expr, tree args)
>      case CPTK_IS_UNION:
>        inform (loc, "  %qT is not a union", t1);
>        break;
> +    case CPTK_IS_ARRAY:
> +      inform (loc, "  %qT is not an array", t1);
> +      break;
>      case CPTK_IS_AGGREGATE:
>        inform (loc, "  %qT is not an aggregate", t1);
>        break;
> diff --git a/gcc/cp/cp-trait.def b/gcc/cp/cp-trait.def
> index 8b7fece0cc8..f68c7f2e8ec 100644
> --- a/gcc/cp/cp-trait.def
> +++ b/gcc/cp/cp-trait.def
> @@ -82,6 +82,7 @@ DEFTRAIT_EXPR (IS_TRIVIALLY_ASSIGNABLE, "__is_trivially_assignable", 2)
>  DEFTRAIT_EXPR (IS_TRIVIALLY_CONSTRUCTIBLE, "__is_trivially_constructible", -1)
>  DEFTRAIT_EXPR (IS_TRIVIALLY_COPYABLE, "__is_trivially_copyable", 1)
>  DEFTRAIT_EXPR (IS_UNION, "__is_union", 1)
> +DEFTRAIT_EXPR (IS_ARRAY, "__is_array", 1)
>  DEFTRAIT_EXPR (REF_CONSTRUCTS_FROM_TEMPORARY, "__reference_constructs_from_temporary", 2)
>  DEFTRAIT_EXPR (REF_CONVERTS_FROM_TEMPORARY, "__reference_converts_from_temporary", 2)
>  /* FIXME Added space to avoid direct usage in GCC 13.  */
> diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
> index 8fb47fd179e..22f2700ec0b 100644
> --- a/gcc/cp/semantics.cc
> +++ b/gcc/cp/semantics.cc
> @@ -12118,6 +12118,9 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2)
>      case CPTK_IS_UNION:
>        return type_code1 == UNION_TYPE;
>
> +    case CPTK_IS_ARRAY:
> +      return type_code1 == ARRAY_TYPE;
> +
>      case CPTK_IS_ASSIGNABLE:
>        return is_xible (MODIFY_EXPR, type1, type2);
>
> @@ -12296,6 +12299,7 @@ finish_trait_expr (location_t loc, cp_trait_kind kind, tree type1, tree type2)
>      case CPTK_IS_ENUM:
>      case CPTK_IS_UNION:
>      case CPTK_IS_SAME:
> +    case CPTK_IS_ARRAY:
>        break;
>
>      case CPTK_IS_LAYOUT_COMPATIBLE:
> diff --git a/gcc/testsuite/g++.dg/ext/has-builtin-1.C b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
> index f343e153e56..56485ae62be 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_array)
> +# error "__has_builtin (__is_array) failed"
> +#endif
> diff --git a/gcc/testsuite/g++.dg/ext/is_array.C b/gcc/testsuite/g++.dg/ext/is_array.C
> new file mode 100644
> index 00000000000..facfed5c7cb
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/ext/is_array.C
> @@ -0,0 +1,28 @@
> +// { 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, X, expect) \
> +  SA(TRAIT(X) == expect);                  \
> +  SA(TRAIT(const X) == expect);            \
> +  SA(TRAIT(volatile X) == expect);         \
> +  SA(TRAIT(const volatile X) == expect)
> +
> +SA_TEST_CATEGORY(__is_array, int[2], true);
> +SA_TEST_CATEGORY(__is_array, int[], true);
> +SA_TEST_CATEGORY(__is_array, int[2][3], true);
> +SA_TEST_CATEGORY(__is_array, int[][3], true);
> +SA_TEST_CATEGORY(__is_array, float*[2], true);
> +SA_TEST_CATEGORY(__is_array, float*[], true);
> +SA_TEST_CATEGORY(__is_array, float*[2][3], true);
> +SA_TEST_CATEGORY(__is_array, float*[][3], true);
> +SA_TEST_CATEGORY(__is_array, ClassType[2], true);
> +SA_TEST_CATEGORY(__is_array, ClassType[], true);
> +SA_TEST_CATEGORY(__is_array, ClassType[2][3], true);
> +SA_TEST_CATEGORY(__is_array, ClassType[][3], true);
> +
> +// Sanity check.
> +SA_TEST_CATEGORY(__is_array, ClassType, false);
> --
> 2.41.0
>

[PATCH v3 1/2] c++: implement __is_array built-in trait

[Ken Matsui]

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

gcc/cp/ChangeLog:

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

gcc/testsuite/ChangeLog:

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

Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
---
 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_array.C      | 28 ++++++++++++++++++++++++
 5 files changed, 39 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/ext/is_array.C

diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 8cf0f2d0974..7cec7eba591 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -3751,6 +3751,9 @@ diagnose_trait_expr (tree expr, tree args)
     case CPTK_IS_UNION:
       inform (loc, "  %qT is not a union", t1);
       break;
+    case CPTK_IS_ARRAY:
+      inform (loc, "  %qT is not an array", t1);
+      break;
     case CPTK_IS_AGGREGATE:
       inform (loc, "  %qT is not an aggregate", t1);
       break;
diff --git a/gcc/cp/cp-trait.def b/gcc/cp/cp-trait.def
index 8b7fece0cc8..f68c7f2e8ec 100644
--- a/gcc/cp/cp-trait.def
+++ b/gcc/cp/cp-trait.def
@@ -82,6 +82,7 @@ DEFTRAIT_EXPR (IS_TRIVIALLY_ASSIGNABLE, "__is_trivially_assignable", 2)
 DEFTRAIT_EXPR (IS_TRIVIALLY_CONSTRUCTIBLE, "__is_trivially_constructible", -1)
 DEFTRAIT_EXPR (IS_TRIVIALLY_COPYABLE, "__is_trivially_copyable", 1)
 DEFTRAIT_EXPR (IS_UNION, "__is_union", 1)
+DEFTRAIT_EXPR (IS_ARRAY, "__is_array", 1)
 DEFTRAIT_EXPR (REF_CONSTRUCTS_FROM_TEMPORARY, "__reference_constructs_from_temporary", 2)
 DEFTRAIT_EXPR (REF_CONVERTS_FROM_TEMPORARY, "__reference_converts_from_temporary", 2)
 /* FIXME Added space to avoid direct usage in GCC 13.  */
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 8fb47fd179e..22f2700ec0b 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -12118,6 +12118,9 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2)
     case CPTK_IS_UNION:
       return type_code1 == UNION_TYPE;
 
+    case CPTK_IS_ARRAY:
+      return type_code1 == ARRAY_TYPE;
+
     case CPTK_IS_ASSIGNABLE:
       return is_xible (MODIFY_EXPR, type1, type2);
 
@@ -12296,6 +12299,7 @@ finish_trait_expr (location_t loc, cp_trait_kind kind, tree type1, tree type2)
     case CPTK_IS_ENUM:
     case CPTK_IS_UNION:
     case CPTK_IS_SAME:
+    case CPTK_IS_ARRAY:
       break;
 
     case CPTK_IS_LAYOUT_COMPATIBLE:
diff --git a/gcc/testsuite/g++.dg/ext/has-builtin-1.C b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
index f343e153e56..56485ae62be 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_array)
+# error "__has_builtin (__is_array) failed"
+#endif
diff --git a/gcc/testsuite/g++.dg/ext/is_array.C b/gcc/testsuite/g++.dg/ext/is_array.C
new file mode 100644
index 00000000000..facfed5c7cb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/is_array.C
@@ -0,0 +1,28 @@
+// { 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, X, expect) \
+  SA(TRAIT(X) == expect);                  \
+  SA(TRAIT(const X) == expect);            \
+  SA(TRAIT(volatile X) == expect);         \
+  SA(TRAIT(const volatile X) == expect)
+
+SA_TEST_CATEGORY(__is_array, int[2], true);
+SA_TEST_CATEGORY(__is_array, int[], true);
+SA_TEST_CATEGORY(__is_array, int[2][3], true);
+SA_TEST_CATEGORY(__is_array, int[][3], true);
+SA_TEST_CATEGORY(__is_array, float*[2], true);
+SA_TEST_CATEGORY(__is_array, float*[], true);
+SA_TEST_CATEGORY(__is_array, float*[2][3], true);
+SA_TEST_CATEGORY(__is_array, float*[][3], true);
+SA_TEST_CATEGORY(__is_array, ClassType[2], true);
+SA_TEST_CATEGORY(__is_array, ClassType[], true);
+SA_TEST_CATEGORY(__is_array, ClassType[2][3], true);
+SA_TEST_CATEGORY(__is_array, ClassType[][3], true);
+
+// Sanity check.
+SA_TEST_CATEGORY(__is_array, ClassType, false);
-- 
2.41.0

[PATCH v3 2/2] libstdc++: use new built-in trait __is_array

[Ken Matsui]

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

libstdc++-v3/ChangeLog:

	* include/std/type_traits (is_array): Use __is_array built-in trait.
	(is_array_v): Likewise.

Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
---
 libstdc++-v3/include/std/type_traits | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index 0e7a9c9c7f3..f2a3a327e7d 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -503,6 +503,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     { };
 
   /// is_array
+#if __has_builtin(__is_array)
+  template<typename _Tp>
+    struct is_array
+    : public __bool_constant<__is_array(_Tp)>
+    { };
+#else
   template<typename>
     struct is_array
     : public false_type { };
@@ -514,6 +520,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _Tp>
     struct is_array<_Tp[]>
     : public true_type { };
+#endif
 
   template<typename>
     struct __is_pointer_helper
@@ -3161,12 +3168,17 @@ template <typename _Tp>
 template <typename _Tp>
   inline constexpr bool is_floating_point_v = is_floating_point<_Tp>::value;
 
+#if __has_builtin(__is_array)
+template <typename _Tp>
+  inline constexpr bool is_array_v = __is_array(_Tp);
+#else
 template <typename _Tp>
   inline constexpr bool is_array_v = false;
 template <typename _Tp>
   inline constexpr bool is_array_v<_Tp[]> = true;
 template <typename _Tp, size_t _Num>
   inline constexpr bool is_array_v<_Tp[_Num]> = true;
+#endif
 
 template <typename _Tp>
   inline constexpr bool is_pointer_v = is_pointer<_Tp>::value;
-- 
2.41.0

[PING][PATCH v3 2/2] libstdc++: use new built-in trait __is_array

[Ken Matsui]

Ping for the use of __is_array built-in.

Sincerely,
Ken Matsui

On Fri, Jul 7, 2023 at 10:24 PM Ken Matsui <kmatsui@gcc.gnu.org> wrote:
>
> This patch lets libstdc++ use new built-in trait __is_array.
>
> libstdc++-v3/ChangeLog:
>
>         * include/std/type_traits (is_array): Use __is_array built-in trait.
>         (is_array_v): Likewise.
>
> Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> ---
>  libstdc++-v3/include/std/type_traits | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
> index 0e7a9c9c7f3..f2a3a327e7d 100644
> --- a/libstdc++-v3/include/std/type_traits
> +++ b/libstdc++-v3/include/std/type_traits
> @@ -503,6 +503,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>      { };
>
>    /// is_array
> +#if __has_builtin(__is_array)
> +  template<typename _Tp>
> +    struct is_array
> +    : public __bool_constant<__is_array(_Tp)>
> +    { };
> +#else
>    template<typename>
>      struct is_array
>      : public false_type { };
> @@ -514,6 +520,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    template<typename _Tp>
>      struct is_array<_Tp[]>
>      : public true_type { };
> +#endif
>
>    template<typename>
>      struct __is_pointer_helper
> @@ -3161,12 +3168,17 @@ template <typename _Tp>
>  template <typename _Tp>
>    inline constexpr bool is_floating_point_v = is_floating_point<_Tp>::value;
>
> +#if __has_builtin(__is_array)
> +template <typename _Tp>
> +  inline constexpr bool is_array_v = __is_array(_Tp);
> +#else
>  template <typename _Tp>
>    inline constexpr bool is_array_v = false;
>  template <typename _Tp>
>    inline constexpr bool is_array_v<_Tp[]> = true;
>  template <typename _Tp, size_t _Num>
>    inline constexpr bool is_array_v<_Tp[_Num]> = true;
> +#endif
>
>  template <typename _Tp>
>    inline constexpr bool is_pointer_v = is_pointer<_Tp>::value;
> --
> 2.41.0
>