[gcc r15-375] c++: Implement __array_rank built-in trait

[gcc r15-375] c++: Implement __array_rank built-in trait

[Ken Matsui]

https://gcc.gnu.org/g:37fad797adea340307fb33c3d7a0a17652063a33

commit r15-375-g37fad797adea340307fb33c3d7a0a17652063a33
Author: Ken Matsui <kmatsui@gcc.gnu.org>
Date:   Thu Feb 15 07:17:31 2024 -0800

    c++: Implement __array_rank built-in trait
    
    This patch implements built-in trait for std::rank.
    
    gcc/cp/ChangeLog:
    
            * cp-trait.def: Define __array_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 __array_rank.
            * g++.dg/ext/rank.C: New test.
    
    Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
    Reviewed-by: Jason Merrill <jason@redhat.com>

Diff:
---
 gcc/cp/constraint.cc                     |  3 +++
 gcc/cp/cp-trait.def                      |  1 +
 gcc/cp/semantics.cc                      | 24 +++++++++++++++++++++---
 gcc/testsuite/g++.dg/ext/has-builtin-1.C |  3 +++
 gcc/testsuite/g++.dg/ext/rank.C          | 24 ++++++++++++++++++++++++
 5 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index d4cc88504863..c28d7bf428ee 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -3871,6 +3871,9 @@ 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 2d1cb7c227c0..b1c875a6e7d4 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, "__array_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 d499b858057c..bde26e4f2bb4 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -12646,6 +12646,10 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2)
     case CPTK_IS_DEDUCIBLE:
       return type_targs_deducible_from (type1, type2);
 
+    /* __array_rank is handled in finish_trait_expr. */
+    case CPTK_RANK:
+      gcc_unreachable ();
+
 #define DEFTRAIT_TYPE(CODE, NAME, ARITY) \
     case CPTK_##CODE:
 #include "cp-trait.def"
@@ -12769,7 +12773,10 @@ 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;
@@ -12862,6 +12869,7 @@ 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:
@@ -12893,8 +12901,18 @@ 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 __array_rank = 0;
+      for (; TREE_CODE (type1) == ARRAY_TYPE; type1 = TREE_TYPE (type1))
+	++__array_rank;
+      val = build_int_cst (size_type_node, __array_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 d2e6a5b4dcb3..bcaa56a7bc5c 100644
--- a/gcc/testsuite/g++.dg/ext/has-builtin-1.C
+++ b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
@@ -11,6 +11,9 @@
 #if !__has_builtin (__add_rvalue_reference)
 # error "__has_builtin (__add_rvalue_reference) failed"
 #endif
+#if !__has_builtin (__array_rank)
+# error "__has_builtin (__array_rank) failed"
+#endif
 #if !__has_builtin (__builtin_addressof)
 # error "__has_builtin (__builtin_addressof) 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 000000000000..0ab2f235036b
--- /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(__array_rank(int) == 0);
+SA(__array_rank(int[2]) == 1);
+SA(__array_rank(int[][4]) == 2);
+SA(__array_rank(int[2][2][4][4][6][6]) == 6);
+SA(__array_rank(ClassType) == 0);
+SA(__array_rank(ClassType[2]) == 1);
+SA(__array_rank(ClassType[][4]) == 2);
+SA(__array_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(__array_rank(T)); }
+
+template void g<int>();