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

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

[Ken Matsui]

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

gcc/cp/ChangeLog:

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

gcc/testsuite/ChangeLog:

	* g++.dg/ext/has-builtin-1.C: Test existence of __is_const.
	* g++.dg/ext/is_const.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_const.C      | 19 +++++++++++++++++++
 5 files changed, 30 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/ext/is_const.C

diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 273d15ab097..1efd5bbdb42 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_CONST:
+      inform (loc, "  %qT is not a const type", 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..9b9f0b240b1 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_CONST, "__is_const", 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..5fe6a0933c1 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -11992,6 +11992,9 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2)
     case CPTK_IS_ENUM:
       return type_code1 == ENUMERAL_TYPE;
 
+    case CPTK_IS_CONST:
+      return CP_TYPE_CONST_P (type1);
+
     case CPTK_IS_FINAL:
       return CLASS_TYPE_P (type1) && CLASSTYPE_FINAL (type1);
 
@@ -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_CONST:
       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..965309a333a 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_const)
+# error "__has_builtin (__is_const) failed"
+#endif
diff --git a/gcc/testsuite/g++.dg/ext/is_const.C b/gcc/testsuite/g++.dg/ext/is_const.C
new file mode 100644
index 00000000000..8f2d7c2fce9
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/is_const.C
@@ -0,0 +1,19 @@
+// { dg-do compile { target c++11 } }
+
+#include <testsuite_tr1.h>
+
+using namespace __gnu_test;
+
+#define SA(X) static_assert((X),#X)
+
+// Positive tests.
+SA(__is_const(const int));
+SA(__is_const(const volatile int));
+SA(__is_const(cClassType));
+SA(__is_const(cvClassType));
+
+// Negative tests.
+SA(!__is_const(int));
+SA(!__is_const(volatile int));
+SA(!__is_const(ClassType));
+SA(!__is_const(vClassType));
-- 
2.40.0

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

[Ken Matsui]

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

libstdc++-v3/ChangeLog:

	* include/std/type_traits (is_const): Use __is_const 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..e77de828501 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -764,6 +764,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   // Type properties.
 
   /// is_const
+#if __has_builtin(__is_const)
+  template<typename _Tp>
+    struct is_const
+    : public __bool_constant<__is_const(_Tp)>
+    { };
+#else
   template<typename>
     struct is_const
     : public false_type { };
@@ -771,6 +777,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _Tp>
     struct is_const<_Tp const>
     : public true_type { };
+#endif
 
   /// is_volatile
   template<typename>
-- 
2.40.0

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

[Patrick Palka]

On Tue, 21 Mar 2023, Ken Matsui wrote:

> This patch lets libstdc++ use new built-in trait __is_const.
> 
> libstdc++-v3/ChangeLog:
> 
> 	* include/std/type_traits (is_const): Use __is_const built-in trait.

We should also use it in is_const_v (likewise for the __is_array and
__is_volatile patches).

> ---
>  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..e77de828501 100644
> --- a/libstdc++-v3/include/std/type_traits
> +++ b/libstdc++-v3/include/std/type_traits
> @@ -764,6 +764,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    // Type properties.
>  
>    /// is_const
> +#if __has_builtin(__is_const)
> +  template<typename _Tp>
> +    struct is_const
> +    : public __bool_constant<__is_const(_Tp)>
> +    { };
> +#else
>    template<typename>
>      struct is_const
>      : public false_type { };
> @@ -771,6 +777,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    template<typename _Tp>
>      struct is_const<_Tp const>
>      : public true_type { };
> +#endif
>  
>    /// is_volatile
>    template<typename>
> -- 
> 2.40.0
> 
> 

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

[Ken Matsui]

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

gcc/cp/ChangeLog:

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

gcc/testsuite/ChangeLog:

	* g++.dg/ext/has-builtin-1.C: Test existence of __is_const.
	* g++.dg/ext/is_const.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_const.C      | 19 +++++++++++++++++++
 5 files changed, 30 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/ext/is_const.C

diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 8cf0f2d0974..ff4ae831def 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_CONST:
+      inform (loc, "  %qT is not a const type", 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..b40b475b86d 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_CONST, "__is_const", 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..011ba8e46e1 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -12079,6 +12079,9 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2)
     case CPTK_IS_ENUM:
       return type_code1 == ENUMERAL_TYPE;
 
+    case CPTK_IS_CONST:
+      return CP_TYPE_CONST_P (type1);
+
     case CPTK_IS_FINAL:
       return CLASS_TYPE_P (type1) && CLASSTYPE_FINAL (type1);
 
@@ -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_CONST:
       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..965309a333a 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_const)
+# error "__has_builtin (__is_const) failed"
+#endif
diff --git a/gcc/testsuite/g++.dg/ext/is_const.C b/gcc/testsuite/g++.dg/ext/is_const.C
new file mode 100644
index 00000000000..8f2d7c2fce9
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/is_const.C
@@ -0,0 +1,19 @@
+// { dg-do compile { target c++11 } }
+
+#include <testsuite_tr1.h>
+
+using namespace __gnu_test;
+
+#define SA(X) static_assert((X),#X)
+
+// Positive tests.
+SA(__is_const(const int));
+SA(__is_const(const volatile int));
+SA(__is_const(cClassType));
+SA(__is_const(cvClassType));
+
+// Negative tests.
+SA(!__is_const(int));
+SA(!__is_const(volatile int));
+SA(!__is_const(ClassType));
+SA(!__is_const(vClassType));
-- 
2.41.0

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

[Ken Matsui]

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

libstdc++-v3/ChangeLog:

	* include/std/type_traits (is_const): Use __is_const built-in trait.
	(is_const_v): Likewise.

Signed-off-by: Ken Matsui <kmatsui@cs.washington.edu>
---
 libstdc++-v3/include/std/type_traits | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index 0e7a9c9c7f3..3a46eca5377 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -764,6 +764,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   // Type properties.
 
   /// is_const
+#if __has_builtin(__is_const)
+  template<typename _Tp>
+    struct is_const
+    : public __bool_constant<__is_const(_Tp)>
+    { };
+#else
   template<typename>
     struct is_const
     : public false_type { };
@@ -771,6 +777,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _Tp>
     struct is_const<_Tp const>
     : public true_type { };
+#endif
 
   /// is_volatile
   template<typename>
@@ -3210,10 +3217,17 @@ template <typename _Tp>
   inline constexpr bool is_compound_v = is_compound<_Tp>::value;
 template <typename _Tp>
   inline constexpr bool is_member_pointer_v = is_member_pointer<_Tp>::value;
+
+#if __has_builtin(__is_const)
+template <typename _Tp>
+  inline constexpr bool is_const_v = __is_const(_Tp);
+#else
 template <typename _Tp>
   inline constexpr bool is_const_v = false;
 template <typename _Tp>
   inline constexpr bool is_const_v<const _Tp> = true;
+#endif
+
 template <typename _Tp>
   inline constexpr bool is_volatile_v = false;
 template <typename _Tp>
-- 
2.41.0

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

[Xi Ruoyao]

Please use [PATCH v3 1/2] next time, now it's not easy to find the
latest version of the series (I'm not sure if the number "3" is
correct).

On Sat, 2023-06-24 at 03:38 -0700, Ken Matsui via Gcc-patches wrote:
> This patch implements built-in trait for std::is_const.
> 
> gcc/cp/ChangeLog:
> 
>         * cp-trait.def: Define __is_const.
>         * constraint.cc (diagnose_trait_expr): Handle CPTK_IS_CONST.
>         * semantics.cc (trait_expr_value): Likewise.
>         (finish_trait_expr): Likewise.
> 
> gcc/testsuite/ChangeLog:
> 
>         * g++.dg/ext/has-builtin-1.C: Test existence of __is_const.
>         * g++.dg/ext/is_const.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_const.C      | 19 +++++++++++++++++++
>  5 files changed, 30 insertions(+)
>  create mode 100644 gcc/testsuite/g++.dg/ext/is_const.C
> 
> diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
> index 8cf0f2d0974..ff4ae831def 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_CONST:
> +      inform (loc, "  %qT is not a const type", 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..b40b475b86d 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_CONST, "__is_const", 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..011ba8e46e1 100644
> --- a/gcc/cp/semantics.cc
> +++ b/gcc/cp/semantics.cc
> @@ -12079,6 +12079,9 @@ trait_expr_value (cp_trait_kind kind, tree
> type1, tree type2)
>      case CPTK_IS_ENUM:
>        return type_code1 == ENUMERAL_TYPE;
>  
> +    case CPTK_IS_CONST:
> +      return CP_TYPE_CONST_P (type1);
> +
>      case CPTK_IS_FINAL:
>        return CLASS_TYPE_P (type1) && CLASSTYPE_FINAL (type1);
>  
> @@ -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_CONST:
>        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..965309a333a 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_const)
> +# error "__has_builtin (__is_const) failed"
> +#endif
> diff --git a/gcc/testsuite/g++.dg/ext/is_const.C
> b/gcc/testsuite/g++.dg/ext/is_const.C
> new file mode 100644
> index 00000000000..8f2d7c2fce9
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/ext/is_const.C
> @@ -0,0 +1,19 @@
> +// { dg-do compile { target c++11 } }
> +
> +#include <testsuite_tr1.h>
> +
> +using namespace __gnu_test;
> +
> +#define SA(X) static_assert((X),#X)
> +
> +// Positive tests.
> +SA(__is_const(const int));
> +SA(__is_const(const volatile int));
> +SA(__is_const(cClassType));
> +SA(__is_const(cvClassType));
> +
> +// Negative tests.
> +SA(!__is_const(int));
> +SA(!__is_const(volatile int));
> +SA(!__is_const(ClassType));
> +SA(!__is_const(vClassType));

-- 
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University

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

[Ken Matsui]

[-- Attachment #1: Type: text/plain, Size: 4703 bytes --]

Sure. Thank you.

On Sat, Jun 24, 2023 at 5:14 AM Xi Ruoyao <xry111@xry111.site> wrote:

> Please use [PATCH v3 1/2] next time, now it's not easy to find the
> latest version of the series (I'm not sure if the number "3" is
> correct).
>
> On Sat, 2023-06-24 at 03:38 -0700, Ken Matsui via Gcc-patches wrote:
> > This patch implements built-in trait for std::is_const.
> >
> > gcc/cp/ChangeLog:
> >
> >         * cp-trait.def: Define __is_const.
> >         * constraint.cc (diagnose_trait_expr): Handle CPTK_IS_CONST.
> >         * semantics.cc (trait_expr_value): Likewise.
> >         (finish_trait_expr): Likewise.
> >
> > gcc/testsuite/ChangeLog:
> >
> >         * g++.dg/ext/has-builtin-1.C: Test existence of __is_const.
> >         * g++.dg/ext/is_const.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_const.C      | 19 +++++++++++++++++++
> >  5 files changed, 30 insertions(+)
> >  create mode 100644 gcc/testsuite/g++.dg/ext/is_const.C
> >
> > diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
> > index 8cf0f2d0974..ff4ae831def 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_CONST:
> > +      inform (loc, "  %qT is not a const type", 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..b40b475b86d 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_CONST, "__is_const", 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..011ba8e46e1 100644
> > --- a/gcc/cp/semantics.cc
> > +++ b/gcc/cp/semantics.cc
> > @@ -12079,6 +12079,9 @@ trait_expr_value (cp_trait_kind kind, tree
> > type1, tree type2)
> >      case CPTK_IS_ENUM:
> >        return type_code1 == ENUMERAL_TYPE;
> >
> > +    case CPTK_IS_CONST:
> > +      return CP_TYPE_CONST_P (type1);
> > +
> >      case CPTK_IS_FINAL:
> >        return CLASS_TYPE_P (type1) && CLASSTYPE_FINAL (type1);
> >
> > @@ -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_CONST:
> >        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..965309a333a 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_const)
> > +# error "__has_builtin (__is_const) failed"
> > +#endif
> > diff --git a/gcc/testsuite/g++.dg/ext/is_const.C
> > b/gcc/testsuite/g++.dg/ext/is_const.C
> > new file mode 100644
> > index 00000000000..8f2d7c2fce9
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/ext/is_const.C
> > @@ -0,0 +1,19 @@
> > +// { dg-do compile { target c++11 } }
> > +
> > +#include <testsuite_tr1.h>
> > +
> > +using namespace __gnu_test;
> > +
> > +#define SA(X) static_assert((X),#X)
> > +
> > +// Positive tests.
> > +SA(__is_const(const int));
> > +SA(__is_const(const volatile int));
> > +SA(__is_const(cClassType));
> > +SA(__is_const(cvClassType));
> > +
> > +// Negative tests.
> > +SA(!__is_const(int));
> > +SA(!__is_const(volatile int));
> > +SA(!__is_const(ClassType));
> > +SA(!__is_const(vClassType));
>
> --
> Xi Ruoyao <xry111@xry111.site>
> School of Aerospace Science and Technology, Xidian University
>
-- 
Sincerely,
Ken Matsui

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

[Ken Matsui]

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

gcc/cp/ChangeLog:

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

gcc/testsuite/ChangeLog:

	* g++.dg/ext/has-builtin-1.C: Test existence of __is_const.
	* g++.dg/ext/is_const.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_const.C      | 19 +++++++++++++++++++
 5 files changed, 30 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/ext/is_const.C

diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 8cf0f2d0974..ff4ae831def 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_CONST:
+      inform (loc, "  %qT is not a const type", 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..b40b475b86d 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_CONST, "__is_const", 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..011ba8e46e1 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -12079,6 +12079,9 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2)
     case CPTK_IS_ENUM:
       return type_code1 == ENUMERAL_TYPE;
 
+    case CPTK_IS_CONST:
+      return CP_TYPE_CONST_P (type1);
+
     case CPTK_IS_FINAL:
       return CLASS_TYPE_P (type1) && CLASSTYPE_FINAL (type1);
 
@@ -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_CONST:
       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..965309a333a 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_const)
+# error "__has_builtin (__is_const) failed"
+#endif
diff --git a/gcc/testsuite/g++.dg/ext/is_const.C b/gcc/testsuite/g++.dg/ext/is_const.C
new file mode 100644
index 00000000000..8f2d7c2fce9
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/is_const.C
@@ -0,0 +1,19 @@
+// { dg-do compile { target c++11 } }
+
+#include <testsuite_tr1.h>
+
+using namespace __gnu_test;
+
+#define SA(X) static_assert((X),#X)
+
+// Positive tests.
+SA(__is_const(const int));
+SA(__is_const(const volatile int));
+SA(__is_const(cClassType));
+SA(__is_const(cvClassType));
+
+// Negative tests.
+SA(!__is_const(int));
+SA(!__is_const(volatile int));
+SA(!__is_const(ClassType));
+SA(!__is_const(vClassType));
-- 
2.41.0

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

[Ken Matsui]

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

libstdc++-v3/ChangeLog:

	* include/std/type_traits (is_const): Use __is_const built-in trait.
	(is_const_v): Likewise.

Signed-off-by: Ken Matsui <kmatsui@cs.washington.edu>
---
 libstdc++-v3/include/std/type_traits | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index 0e7a9c9c7f3..3a46eca5377 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -764,6 +764,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   // Type properties.
 
   /// is_const
+#if __has_builtin(__is_const)
+  template<typename _Tp>
+    struct is_const
+    : public __bool_constant<__is_const(_Tp)>
+    { };
+#else
   template<typename>
     struct is_const
     : public false_type { };
@@ -771,6 +777,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _Tp>
     struct is_const<_Tp const>
     : public true_type { };
+#endif
 
   /// is_volatile
   template<typename>
@@ -3210,10 +3217,17 @@ template <typename _Tp>
   inline constexpr bool is_compound_v = is_compound<_Tp>::value;
 template <typename _Tp>
   inline constexpr bool is_member_pointer_v = is_member_pointer<_Tp>::value;
+
+#if __has_builtin(__is_const)
+template <typename _Tp>
+  inline constexpr bool is_const_v = __is_const(_Tp);
+#else
 template <typename _Tp>
   inline constexpr bool is_const_v = false;
 template <typename _Tp>
   inline constexpr bool is_const_v<const _Tp> = true;
+#endif
+
 template <typename _Tp>
   inline constexpr bool is_volatile_v = false;
 template <typename _Tp>
-- 
2.41.0

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

[Ken Matsui]

Here is the benchmark result for is_const.

https://github.com/ken-matsui/gcc-benches/blob/main/is_const.md#sat-jun-24-044815-am-pdt-2023

Time: -2.86467%
Peak Memory Usage: -1.0654%
Total Memory Usage: -1.62369%

On Sat, Jun 24, 2023 at 6:41 AM Ken Matsui <kmatsui@cs.washington.edu> wrote:
>
> This patch implements built-in trait for std::is_const.
>
> gcc/cp/ChangeLog:
>
>         * cp-trait.def: Define __is_const.
>         * constraint.cc (diagnose_trait_expr): Handle CPTK_IS_CONST.
>         * semantics.cc (trait_expr_value): Likewise.
>         (finish_trait_expr): Likewise.
>
> gcc/testsuite/ChangeLog:
>
>         * g++.dg/ext/has-builtin-1.C: Test existence of __is_const.
>         * g++.dg/ext/is_const.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_const.C      | 19 +++++++++++++++++++
>  5 files changed, 30 insertions(+)
>  create mode 100644 gcc/testsuite/g++.dg/ext/is_const.C
>
> diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
> index 8cf0f2d0974..ff4ae831def 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_CONST:
> +      inform (loc, "  %qT is not a const type", 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..b40b475b86d 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_CONST, "__is_const", 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..011ba8e46e1 100644
> --- a/gcc/cp/semantics.cc
> +++ b/gcc/cp/semantics.cc
> @@ -12079,6 +12079,9 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2)
>      case CPTK_IS_ENUM:
>        return type_code1 == ENUMERAL_TYPE;
>
> +    case CPTK_IS_CONST:
> +      return CP_TYPE_CONST_P (type1);
> +
>      case CPTK_IS_FINAL:
>        return CLASS_TYPE_P (type1) && CLASSTYPE_FINAL (type1);
>
> @@ -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_CONST:
>        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..965309a333a 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_const)
> +# error "__has_builtin (__is_const) failed"
> +#endif
> diff --git a/gcc/testsuite/g++.dg/ext/is_const.C b/gcc/testsuite/g++.dg/ext/is_const.C
> new file mode 100644
> index 00000000000..8f2d7c2fce9
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/ext/is_const.C
> @@ -0,0 +1,19 @@
> +// { dg-do compile { target c++11 } }
> +
> +#include <testsuite_tr1.h>
> +
> +using namespace __gnu_test;
> +
> +#define SA(X) static_assert((X),#X)
> +
> +// Positive tests.
> +SA(__is_const(const int));
> +SA(__is_const(const volatile int));
> +SA(__is_const(cClassType));
> +SA(__is_const(cvClassType));
> +
> +// Negative tests.
> +SA(!__is_const(int));
> +SA(!__is_const(volatile int));
> +SA(!__is_const(ClassType));
> +SA(!__is_const(vClassType));
> --
> 2.41.0
>

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

[Ken Matsui]

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

gcc/cp/ChangeLog:

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

gcc/testsuite/ChangeLog:

	* g++.dg/ext/has-builtin-1.C: Test existence of __is_const.
	* g++.dg/ext/is_const.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_const.C      | 19 +++++++++++++++++++
 5 files changed, 30 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/ext/is_const.C

diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 8cf0f2d0974..ff4ae831def 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_CONST:
+      inform (loc, "  %qT is not a const type", 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..b40b475b86d 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_CONST, "__is_const", 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..011ba8e46e1 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -12079,6 +12079,9 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2)
     case CPTK_IS_ENUM:
       return type_code1 == ENUMERAL_TYPE;
 
+    case CPTK_IS_CONST:
+      return CP_TYPE_CONST_P (type1);
+
     case CPTK_IS_FINAL:
       return CLASS_TYPE_P (type1) && CLASSTYPE_FINAL (type1);
 
@@ -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_CONST:
       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..965309a333a 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_const)
+# error "__has_builtin (__is_const) failed"
+#endif
diff --git a/gcc/testsuite/g++.dg/ext/is_const.C b/gcc/testsuite/g++.dg/ext/is_const.C
new file mode 100644
index 00000000000..8f2d7c2fce9
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/is_const.C
@@ -0,0 +1,19 @@
+// { dg-do compile { target c++11 } }
+
+#include <testsuite_tr1.h>
+
+using namespace __gnu_test;
+
+#define SA(X) static_assert((X),#X)
+
+// Positive tests.
+SA(__is_const(const int));
+SA(__is_const(const volatile int));
+SA(__is_const(cClassType));
+SA(__is_const(cvClassType));
+
+// Negative tests.
+SA(!__is_const(int));
+SA(!__is_const(volatile int));
+SA(!__is_const(ClassType));
+SA(!__is_const(vClassType));
-- 
2.41.0

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

[Ken Matsui]

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

libstdc++-v3/ChangeLog:

	* include/std/type_traits (is_const): Use __is_const built-in trait.
	(is_const_v): Likewise.

Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
---
 libstdc++-v3/include/std/type_traits | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index 0e7a9c9c7f3..3a46eca5377 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -764,6 +764,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   // Type properties.
 
   /// is_const
+#if __has_builtin(__is_const)
+  template<typename _Tp>
+    struct is_const
+    : public __bool_constant<__is_const(_Tp)>
+    { };
+#else
   template<typename>
     struct is_const
     : public false_type { };
@@ -771,6 +777,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _Tp>
     struct is_const<_Tp const>
     : public true_type { };
+#endif
 
   /// is_volatile
   template<typename>
@@ -3210,10 +3217,17 @@ template <typename _Tp>
   inline constexpr bool is_compound_v = is_compound<_Tp>::value;
 template <typename _Tp>
   inline constexpr bool is_member_pointer_v = is_member_pointer<_Tp>::value;
+
+#if __has_builtin(__is_const)
+template <typename _Tp>
+  inline constexpr bool is_const_v = __is_const(_Tp);
+#else
 template <typename _Tp>
   inline constexpr bool is_const_v = false;
 template <typename _Tp>
   inline constexpr bool is_const_v<const _Tp> = true;
+#endif
+
 template <typename _Tp>
   inline constexpr bool is_volatile_v = false;
 template <typename _Tp>
-- 
2.41.0

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

[Ken Matsui]

Ping for the use of __is_const built-in.

Sincerely,
Ken Matsui

On Fri, Jul 7, 2023 at 10:27 PM Ken Matsui <kmatsui@gcc.gnu.org> wrote:
>
> This patch lets libstdc++ use new built-in trait __is_const.
>
> libstdc++-v3/ChangeLog:
>
>         * include/std/type_traits (is_const): Use __is_const built-in trait.
>         (is_const_v): Likewise.
>
> Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> ---
>  libstdc++-v3/include/std/type_traits | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
> index 0e7a9c9c7f3..3a46eca5377 100644
> --- a/libstdc++-v3/include/std/type_traits
> +++ b/libstdc++-v3/include/std/type_traits
> @@ -764,6 +764,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    // Type properties.
>
>    /// is_const
> +#if __has_builtin(__is_const)
> +  template<typename _Tp>
> +    struct is_const
> +    : public __bool_constant<__is_const(_Tp)>
> +    { };
> +#else
>    template<typename>
>      struct is_const
>      : public false_type { };
> @@ -771,6 +777,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    template<typename _Tp>
>      struct is_const<_Tp const>
>      : public true_type { };
> +#endif
>
>    /// is_volatile
>    template<typename>
> @@ -3210,10 +3217,17 @@ template <typename _Tp>
>    inline constexpr bool is_compound_v = is_compound<_Tp>::value;
>  template <typename _Tp>
>    inline constexpr bool is_member_pointer_v = is_member_pointer<_Tp>::value;
> +
> +#if __has_builtin(__is_const)
> +template <typename _Tp>
> +  inline constexpr bool is_const_v = __is_const(_Tp);
> +#else
>  template <typename _Tp>
>    inline constexpr bool is_const_v = false;
>  template <typename _Tp>
>    inline constexpr bool is_const_v<const _Tp> = true;
> +#endif
> +
>  template <typename _Tp>
>    inline constexpr bool is_volatile_v = false;
>  template <typename _Tp>
> --
> 2.41.0
>