[PATCH v14 21/26] c++: Implement __rank built-in trait

[Jason Merrill]

On 2/28/24 11:26, Ken Matsui wrote:
> This patch implements built-in trait for std::rank.

__rank seems too short, maybe __array_rank?

Actually, it occurs to me that perhaps we should have been adding 
__builtin to all of these rather than just __ and the library trait 
name.  I guess it's too late to do that for the GCC 14 traits, but we 
could do it for this group?

> gcc/cp/ChangeLog:
> 
> 	* cp-trait.def: Define __rank.
> 	* constraint.cc (diagnose_trait_expr): Handle CPTK_RANK.
> 	* semantics.cc (trait_expr_value): Likewise.
> 	(finish_trait_expr): Likewise.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/ext/has-builtin-1.C: Test existence of __rank.
> 	* g++.dg/ext/rank.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                      | 23 ++++++++++++++++++++---
>   gcc/testsuite/g++.dg/ext/has-builtin-1.C |  3 +++
>   gcc/testsuite/g++.dg/ext/rank.C          | 24 ++++++++++++++++++++++++
>   5 files changed, 51 insertions(+), 3 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/ext/rank.C
> 
> diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
> index 000df847342..23ea66d9c12 100644
> --- a/gcc/cp/constraint.cc
> +++ b/gcc/cp/constraint.cc
> @@ -3870,6 +3870,9 @@ diagnose_trait_expr (tree expr, tree args)
>       case CPTK_IS_VOLATILE:
>         inform (loc, "  %qT is not a volatile type", t1);
>         break;
> +    case CPTK_RANK:
> +      inform (loc, "  %qT cannot yield a rank", t1);
> +      break;
>       case CPTK_REF_CONSTRUCTS_FROM_TEMPORARY:
>         inform (loc, "  %qT is not a reference that binds to a temporary "
>   	      "object of type %qT (direct-initialization)", t1, t2);
> diff --git a/gcc/cp/cp-trait.def b/gcc/cp/cp-trait.def
> index 2d1cb7c227c..85056c8140b 100644
> --- a/gcc/cp/cp-trait.def
> +++ b/gcc/cp/cp-trait.def
> @@ -99,6 +99,7 @@ DEFTRAIT_EXPR (IS_TRIVIALLY_COPYABLE, "__is_trivially_copyable", 1)
>   DEFTRAIT_EXPR (IS_UNBOUNDED_ARRAY, "__is_unbounded_array", 1)
>   DEFTRAIT_EXPR (IS_UNION, "__is_union", 1)
>   DEFTRAIT_EXPR (IS_VOLATILE, "__is_volatile", 1)
> +DEFTRAIT_EXPR (RANK, "__rank", 1)
>   DEFTRAIT_EXPR (REF_CONSTRUCTS_FROM_TEMPORARY, "__reference_constructs_from_temporary", 2)
>   DEFTRAIT_EXPR (REF_CONVERTS_FROM_TEMPORARY, "__reference_converts_from_temporary", 2)
>   DEFTRAIT_TYPE (REMOVE_ALL_EXTENTS, "__remove_all_extents", 1)
> diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
> index 45dc509855a..7242db75248 100644
> --- a/gcc/cp/semantics.cc
> +++ b/gcc/cp/semantics.cc
> @@ -12550,6 +12550,9 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2)
>       case CPTK_IS_DEDUCIBLE:
>         return type_targs_deducible_from (type1, type2);
>   
> +    /* __rank is handled in finish_trait_expr. */
> +    case CPTK_RANK:

This should have a gcc_unreachable.

> +
>   #define DEFTRAIT_TYPE(CODE, NAME, ARITY) \
>       case CPTK_##CODE:
>   #include "cp-trait.def"
> @@ -12622,7 +12625,10 @@ finish_trait_expr (location_t loc, cp_trait_kind kind, tree type1, tree type2)
>     if (processing_template_decl)
>       {
>         tree trait_expr = make_node (TRAIT_EXPR);
> -      TREE_TYPE (trait_expr) = boolean_type_node;
> +      if (kind == CPTK_RANK)
> +	TREE_TYPE (trait_expr) = size_type_node;
> +      else
> +	TREE_TYPE (trait_expr) = boolean_type_node;
>         TRAIT_EXPR_TYPE1 (trait_expr) = type1;
>         TRAIT_EXPR_TYPE2 (trait_expr) = type2;
>         TRAIT_EXPR_KIND (trait_expr) = kind;
> @@ -12714,6 +12720,7 @@ finish_trait_expr (location_t loc, cp_trait_kind kind, tree type1, tree type2)
>       case CPTK_IS_UNBOUNDED_ARRAY:
>       case CPTK_IS_UNION:
>       case CPTK_IS_VOLATILE:
> +    case CPTK_RANK:
>         break;
>   
>       case CPTK_IS_LAYOUT_COMPATIBLE:
> @@ -12745,8 +12752,18 @@ finish_trait_expr (location_t loc, cp_trait_kind kind, tree type1, tree type2)
>         gcc_unreachable ();
>       }
>   
> -  tree val = (trait_expr_value (kind, type1, type2)
> -	      ? boolean_true_node : boolean_false_node);
> +  tree val;
> +  if (kind == CPTK_RANK)
> +    {
> +      size_t rank = 0;
> +      for (; TREE_CODE (type1) == ARRAY_TYPE; type1 = TREE_TYPE (type1))
> +	++rank;
> +      val = build_int_cst (size_type_node, rank);
> +    }
> +  else
> +    val = (trait_expr_value (kind, type1, type2)
> +	   ? boolean_true_node : boolean_false_node);
> +
>     return maybe_wrap_with_location (val, loc);
>   }
>   
> diff --git a/gcc/testsuite/g++.dg/ext/has-builtin-1.C b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
> index 3aca273aad6..7f7b27f7aa7 100644
> --- a/gcc/testsuite/g++.dg/ext/has-builtin-1.C
> +++ b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
> @@ -179,6 +179,9 @@
>   #if !__has_builtin (__is_volatile)
>   # error "__has_builtin (__is_volatile) failed"
>   #endif
> +#if !__has_builtin (__rank)
> +# error "__has_builtin (__rank) failed"
> +#endif
>   #if !__has_builtin (__reference_constructs_from_temporary)
>   # error "__has_builtin (__reference_constructs_from_temporary) failed"
>   #endif
> diff --git a/gcc/testsuite/g++.dg/ext/rank.C b/gcc/testsuite/g++.dg/ext/rank.C
> new file mode 100644
> index 00000000000..28894184387
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/ext/rank.C
> @@ -0,0 +1,24 @@
> +// { dg-do compile { target c++11 } }
> +
> +#include <cstddef>
> +
> +#define SA(X) static_assert((X),#X)
> +
> +class ClassType { };
> +
> +SA(__rank(int) == 0);
> +SA(__rank(int[2]) == 1);
> +SA(__rank(int[][4]) == 2);
> +SA(__rank(int[2][2][4][4][6][6]) == 6);
> +SA(__rank(ClassType) == 0);
> +SA(__rank(ClassType[2]) == 1);
> +SA(__rank(ClassType[][4]) == 2);
> +SA(__rank(ClassType[2][2][4][4][6][6]) == 6);
> +
> +template<class T> void f(T) = delete;
> +void f(size_t);
> +
> +template<class T>
> +void g() { f(__rank(T)); }
> +
> +template void g<int>();