[PATCH v7 15/22] c++: Implement __add_lvalue_reference built-in trait

[Ken Matsui <kmatsui@gcc.gnu.org>]

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

gcc/cp/ChangeLog:

	* cp-trait.def: Define __add_lvalue_reference.
	* semantics.cc (finish_trait_type): Handle
	CPTK_ADD_LVALUE_REFERENCE.

gcc/testsuite/ChangeLog:

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

Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
---
 gcc/cp/cp-trait.def                           |  1 +
 gcc/cp/semantics.cc                           |  8 +++++++
 .../g++.dg/ext/add_lvalue_reference.C         | 21 +++++++++++++++++++
 gcc/testsuite/g++.dg/ext/has-builtin-1.C      |  3 +++
 4 files changed, 33 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/ext/add_lvalue_reference.C

diff --git a/gcc/cp/cp-trait.def b/gcc/cp/cp-trait.def
index 933c8bcbe68..9a27dca4ea3 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_LVALUE_REFERENCE, "__add_lvalue_reference", 1)
 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)
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 078424dac23..05f5b62f9df 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -12776,6 +12776,14 @@ finish_trait_type (cp_trait_kind kind, tree type1, tree type2,
 
   switch (kind)
     {
+    case CPTK_ADD_LVALUE_REFERENCE:
+      if (VOID_TYPE_P (type1)
+	  || (FUNC_OR_METHOD_TYPE_P (type1)
+	      && (type_memfn_quals (type1) != TYPE_UNQUALIFIED
+		  || type_memfn_rqual (type1) != REF_QUAL_NONE)))
+	return type1;
+      return cp_build_reference_type (type1, /*rval=*/false);
+
     case CPTK_ADD_POINTER:
       if (FUNC_OR_METHOD_TYPE_P (type1)
 	  && (type_memfn_quals (type1) != TYPE_UNQUALIFIED
diff --git a/gcc/testsuite/g++.dg/ext/add_lvalue_reference.C b/gcc/testsuite/g++.dg/ext/add_lvalue_reference.C
new file mode 100644
index 00000000000..8fe1e0300e5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/add_lvalue_reference.C
@@ -0,0 +1,21 @@
+// { dg-do compile { target c++11 } }
+
+#define SA(X) static_assert((X),#X)
+
+class ClassType { };
+
+SA(__is_same(__add_lvalue_reference(int), int&));
+SA(__is_same(__add_lvalue_reference(int&), int&));
+SA(__is_same(__add_lvalue_reference(const int), const int&));
+SA(__is_same(__add_lvalue_reference(int*), int*&));
+SA(__is_same(__add_lvalue_reference(ClassType&), ClassType&));
+SA(__is_same(__add_lvalue_reference(ClassType), ClassType&));
+SA(__is_same(__add_lvalue_reference(int(int)), int(&)(int)));
+SA(__is_same(__add_lvalue_reference(int&&), int&));
+SA(__is_same(__add_lvalue_reference(ClassType&&), ClassType&));
+SA(__is_same(__add_lvalue_reference(void), void));
+SA(__is_same(__add_lvalue_reference(const void), const void));
+SA(__is_same(__add_lvalue_reference(bool(int) const), bool(int) const));
+SA(__is_same(__add_lvalue_reference(bool(int) &), bool(int) &));
+SA(__is_same(__add_lvalue_reference(bool(int) const &&), bool(int) const &&));
+SA(__is_same(__add_lvalue_reference(bool(int)), bool(&)(int)));
diff --git a/gcc/testsuite/g++.dg/ext/has-builtin-1.C b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
index 85b74bd676b..3fca9cfabcc 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_lvalue_reference)
+# error "__has_builtin (__add_lvalue_reference) failed"
+#endif
 #if !__has_builtin (__add_pointer)
 # error "__has_builtin (__add_pointer) failed"
 #endif
-- 
2.43.2