c++: Implement __add_pointer built-in trait

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

gcc/cp/ChangeLog:

	* cp-trait.def: Define __add_pointer.
	* semantics.cc (finish_trait_type): Handle CPTK_ADD_POINTER.
	(object_type_p): New function.
	(referenceable_type_p): Likewise.
	(trait_expr_value): Use object_type_p.

gcc/testsuite/ChangeLog:

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

Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
Reviewed-by: Jason Merrill <jason@redhat.com>

4 files changed, 76 insertions, 3 deletions

diff --git a/gcc/cp/cp-trait.def b/gcc/cp/cp-trait.def
index 05514a5..63f8792 100644
--- a/gcc/cp/cp-trait.def
+++ b/gcc/cp/cp-trait.def
@@ -48,6 +48,7 @@
 #define DEFTRAIT_TYPE_DEFAULTED
 #endif
 
+DEFTRAIT_TYPE (ADD_POINTER, "__add_pointer", 1)
 DEFTRAIT_EXPR (HAS_NOTHROW_ASSIGN, "__has_nothrow_assign", 1)
 DEFTRAIT_EXPR (HAS_NOTHROW_CONSTRUCTOR, "__has_nothrow_constructor", 1)
 DEFTRAIT_EXPR (HAS_NOTHROW_COPY, "__has_nothrow_copy", 1)
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index e49d3e3..4920b56 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -12438,6 +12438,16 @@ fold_builtin_is_corresponding_member (location_t loc, int nargs,
 				   fold_convert (TREE_TYPE (arg1), arg2)));
 }
 
+/* [basic.types] 8.  True iff TYPE is an object type.  */
+
+static bool
+object_type_p (const_tree type)
+{
+  return (TREE_CODE (type) != FUNCTION_TYPE
+          && !TYPE_REF_P (type)
+          && !VOID_TYPE_P (type));
+}
+
 /* Actually evaluates the trait.  */
 
 static bool
@@ -12580,9 +12590,7 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2)
       return is_nothrow_convertible (type1, type2);
 
     case CPTK_IS_OBJECT:
-      return (type_code1 != FUNCTION_TYPE
-	      && type_code1 != REFERENCE_TYPE
-	      && type_code1 != VOID_TYPE);
+      return object_type_p (type1);
 
     case CPTK_IS_POINTER_INTERCONVERTIBLE_BASE_OF:
       return pointer_interconvertible_base_of_p (type1, type2);
@@ -12737,6 +12745,18 @@ same_type_ref_bind_p (cp_trait_kind kind, tree type1, tree type2)
 	      (non_reference (to), non_reference (from))));
 }
 
+/* [defns.referenceable] True iff TYPE is a referenceable type.  */
+
+static bool
+referenceable_type_p (const_tree type)
+{
+  return (TYPE_REF_P (type)
+	  || object_type_p (type)
+	  || (FUNC_OR_METHOD_TYPE_P (type)
+	      && (type_memfn_quals (type) == TYPE_UNQUALIFIED
+		  && type_memfn_rqual (type) == REF_QUAL_NONE)));
+}
+
 /* Process a trait expression.  */
 
 tree
@@ -12904,6 +12924,16 @@ finish_trait_type (cp_trait_kind kind, tree type1, tree type2,
 
   switch (kind)
     {
+    case CPTK_ADD_POINTER:
+      /* [meta.trans.ptr].  */
+      if (VOID_TYPE_P (type1) || referenceable_type_p (type1))
+	{
+	  if (TYPE_REF_P (type1))
+	    type1 = TREE_TYPE (type1);
+	  return build_pointer_type (type1);
+	}
+      return type1;
+
     case CPTK_REMOVE_CV:
       return cv_unqualified (type1);
 
diff --git a/gcc/testsuite/g++.dg/ext/add_pointer.C b/gcc/testsuite/g++.dg/ext/add_pointer.C
new file mode 100644
index 0000000..c405cdd
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/add_pointer.C
@@ -0,0 +1,39 @@
+// { dg-do compile { target c++11 } }
+
+#define SA(X) static_assert((X),#X)
+
+class ClassType { };
+
+SA(__is_same(__add_pointer(int), int*));
+SA(__is_same(__add_pointer(int*), int**));
+SA(__is_same(__add_pointer(const int), const int*));
+SA(__is_same(__add_pointer(int&), int*));
+SA(__is_same(__add_pointer(ClassType*), ClassType**));
+SA(__is_same(__add_pointer(ClassType), ClassType*));
+SA(__is_same(__add_pointer(void), void*));
+SA(__is_same(__add_pointer(const void), const void*));
+SA(__is_same(__add_pointer(volatile void), volatile void*));
+SA(__is_same(__add_pointer(const volatile void), const volatile void*));
+
+void f1();
+using f1_type = decltype(f1);
+using pf1_type = decltype(&f1);
+SA(__is_same(__add_pointer(f1_type), pf1_type));
+
+void f2() noexcept; // PR libstdc++/78361
+using f2_type = decltype(f2);
+using pf2_type = decltype(&f2);
+SA(__is_same(__add_pointer(f2_type), pf2_type));
+
+using fn_type = void();
+using pfn_type = void(*)();
+SA(__is_same(__add_pointer(fn_type), pfn_type));
+
+SA(__is_same(__add_pointer(void() &), void() &));
+SA(__is_same(__add_pointer(void() & noexcept), void() & noexcept));
+SA(__is_same(__add_pointer(void() const), void() const));
+SA(__is_same(__add_pointer(void(...) &), void(...) &));
+SA(__is_same(__add_pointer(void(...) & noexcept), void(...) & noexcept));
+SA(__is_same(__add_pointer(void(...) const), void(...) const));
+
+SA(__is_same(__add_pointer(void() __restrict), void() __restrict));
diff --git a/gcc/testsuite/g++.dg/ext/has-builtin-1.C b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
index 1e10c87..bd9e064 100644
--- a/gcc/testsuite/g++.dg/ext/has-builtin-1.C
+++ b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
@@ -2,6 +2,9 @@
 // { dg-do compile }
 // Verify that __has_builtin gives the correct answer for C++ built-ins.
 
+#if !__has_builtin (__add_pointer)
+# error "__has_builtin (__add_pointer) failed"
+#endif
 #if !__has_builtin (__builtin_addressof)
 # error "__has_builtin (__builtin_addressof) failed"
 #endif