c++: Implement __is_volatile built-in trait

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

gcc/cp/ChangeLog:

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

gcc/testsuite/ChangeLog:

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

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

5 files changed, 31 insertions, 0 deletions

diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index eaf17a5..d9caf54 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -3862,6 +3862,9 @@ diagnose_trait_expr (tree expr, tree args)
     case CPTK_IS_UNION:
       inform (loc, "  %qT is not a union", t1);
       break;
+    case CPTK_IS_VOLATILE:
+      inform (loc, "  %qT is not a volatile type", 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 36faed9..e934745 100644
--- a/gcc/cp/cp-trait.def
+++ b/gcc/cp/cp-trait.def
@@ -92,6 +92,7 @@ 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_VOLATILE, "__is_volatile", 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_CV, "__remove_cv", 1)
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index b4cda21..634a324 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -12618,6 +12618,9 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2)
     case CPTK_IS_UNION:
       return type_code1 == UNION_TYPE;
 
+    case CPTK_IS_VOLATILE:
+      return CP_TYPE_VOLATILE_P (type1);
+
     case CPTK_REF_CONSTRUCTS_FROM_TEMPORARY:
       return ref_xes_from_temporary (type1, type2, /*direct_init=*/true);
 
@@ -12828,6 +12831,7 @@ finish_trait_expr (location_t loc, cp_trait_kind kind, tree type1, tree type2)
     case CPTK_IS_SAME:
     case CPTK_IS_SCOPED_ENUM:
     case CPTK_IS_UNION:
+    case CPTK_IS_VOLATILE:
       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 e3640fa..b2e2f2f 100644
--- a/gcc/testsuite/g++.dg/ext/has-builtin-1.C
+++ b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
@@ -158,6 +158,9 @@
 #if !__has_builtin (__is_union)
 # error "__has_builtin (__is_union) failed"
 #endif
+#if !__has_builtin (__is_volatile)
+# error "__has_builtin (__is_volatile) 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/is_volatile.C b/gcc/testsuite/g++.dg/ext/is_volatile.C
new file mode 100644
index 0000000..80a1cfc
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/is_volatile.C
@@ -0,0 +1,20 @@
+// { dg-do compile { target c++11 } }
+
+#define SA(X) static_assert((X),#X)
+
+class ClassType { };
+using cClassType = const ClassType;
+using vClassType = volatile ClassType;
+using cvClassType = const volatile ClassType;
+
+// Positive tests.
+SA(__is_volatile(volatile int));
+SA(__is_volatile(const volatile int));
+SA(__is_volatile(vClassType));
+SA(__is_volatile(cvClassType));
+
+// Negative tests.
+SA(!__is_volatile(int));
+SA(!__is_volatile(const int));
+SA(!__is_volatile(ClassType));
+SA(!__is_volatile(cClassType));