[C++ PATCH] Implement LWG2296 helper intrinsic

[Jakub Jelinek <jakub@redhat.com>]

Hi!

The following patch adds __builtin_addressof with the semantics it has in
clang, i.e. it is a constexpr & operator alternative that never uses the
overloaded & operator.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2016-10-07  Jakub Jelinek  <jakub@redhat.com>

	Implement LWG2296 helper intrinsic
c-family/
	* c-common.h (enum rid): Add RID_ADDRESSOF.
	* c-common.c (c_common_reswords): Add __builtin_addressof.
cp/
	* parser.c (cp_parser_postfix_expression): Handle RID_ADDRESSOF.
	* cp-objcp-common.c (cp_common_init_ts): Handle ADDRESSOF_EXPR.
	* constexpr.c (potential_constant_expression_1): Likewise.
	* error.c (dump_expr): Likewise.
	* typeck.c (cp_build_addressof): New function.
	* cp-tree.h (cp_build_addressof): Declare.
	* cxx-pretty-print.h (pp_cxx_addressof_expression): Declare.
	* cp-tree.def (ADDRESSOF_EXPR): New tree code.
	* cxx-pretty-print.c (cxx_pretty_printer::primary_expression): Handle
	ADDRESSOF_EXPR.  Add __builtin_addressof and
	__has_unique_object_representations into syntax in function comment.
	(pp_cxx_addressof_expression): New function.
	* pt.c (tsubst_copy_and_build): Handle ADDRESSOF_EXPR.
testsuite/
	* g++.dg/cpp0x/addressof1.C: New test.
	* g++.dg/cpp0x/addressof2.C: New test.

--- gcc/c-family/c-common.h.jj	2016-10-06 23:16:43.347087129 +0200
+++ gcc/c-family/c-common.h	2016-10-07 09:24:56.377835519 +0200
@@ -146,6 +146,7 @@ enum rid
   RID_CONSTCAST, RID_DYNCAST, RID_REINTCAST, RID_STATCAST,
 
   /* C++ extensions */
+  RID_ADDRESSOF,
   RID_BASES,                   RID_DIRECT_BASES,
   RID_HAS_NOTHROW_ASSIGN,      RID_HAS_NOTHROW_CONSTRUCTOR,
   RID_HAS_NOTHROW_COPY,        RID_HAS_TRIVIAL_ASSIGN,
--- gcc/c-family/c-common.c.jj	2016-10-06 23:16:43.351087082 +0200
+++ gcc/c-family/c-common.c	2016-10-07 09:24:56.380835482 +0200
@@ -463,6 +463,7 @@ const struct c_common_resword c_common_r
   { "__attribute__",	RID_ATTRIBUTE,	0 },
   { "__auto_type",	RID_AUTO_TYPE,	D_CONLY },
   { "__bases",          RID_BASES, D_CXXONLY },
+  { "__builtin_addressof", RID_ADDRESSOF, D_CXXONLY },
   { "__builtin_call_with_static_chain",
     RID_BUILTIN_CALL_WITH_STATIC_CHAIN, D_CONLY },
   { "__builtin_choose_expr", RID_CHOOSE_EXPR, D_CONLY },
--- gcc/cp/parser.c.jj	2016-10-06 23:16:43.362086951 +0200
+++ gcc/cp/parser.c	2016-10-07 09:55:18.386923503 +0200
@@ -6602,6 +6602,7 @@ cp_parser_postfix_expression (cp_parser
 	break;
       }
 
+    case RID_ADDRESSOF:
     case RID_BUILTIN_SHUFFLE:
       {
 	vec<tree, va_gc> *vec;
@@ -6618,19 +6619,29 @@ cp_parser_postfix_expression (cp_parser
 	FOR_EACH_VEC_ELT (*vec, i, p)
 	  mark_exp_read (p);
 
-	if (vec->length () == 2)
-	  return build_x_vec_perm_expr (loc, (*vec)[0], NULL_TREE, (*vec)[1],
-					 tf_warning_or_error);
-	else if (vec->length () == 3)
-	  return build_x_vec_perm_expr (loc, (*vec)[0], (*vec)[1], (*vec)[2],
-					 tf_warning_or_error);
-	else
-	{
-	  error_at (loc, "wrong number of arguments to "
-	      "%<__builtin_shuffle%>");
-	  return error_mark_node;
-	}
-	break;
+	switch (keyword)
+	  {
+	  case RID_ADDRESSOF:
+	    if (vec->length () == 1)
+	      return cp_build_addressof (loc, (*vec)[0], tf_warning_or_error);
+	    error_at (loc, "wrong number of arguments to "
+			   "%<__builtin_addressof%>");
+	    return error_mark_node;
+
+	  case RID_BUILTIN_SHUFFLE:
+	    if (vec->length () == 2)
+	      return build_x_vec_perm_expr (loc, (*vec)[0], NULL_TREE,
+					    (*vec)[1], tf_warning_or_error);
+	    else if (vec->length () == 3)
+	      return build_x_vec_perm_expr (loc, (*vec)[0], (*vec)[1],
+					    (*vec)[2], tf_warning_or_error);
+	    error_at (loc, "wrong number of arguments to "
+			   "%<__builtin_shuffle%>");
+	    return error_mark_node;
+
+	  default:
+	    gcc_unreachable ();
+	  }
       }
 
     default:
--- gcc/cp/cp-objcp-common.c.jj	2016-10-06 17:46:29.000000000 +0200
+++ gcc/cp/cp-objcp-common.c	2016-10-07 09:55:18.391923440 +0200
@@ -315,6 +315,7 @@ cp_common_init_ts (void)
   MARK_TS_TYPED (STMT_EXPR);
   MARK_TS_TYPED (OFFSET_REF);
   MARK_TS_TYPED (OFFSETOF_EXPR);
+  MARK_TS_TYPED (ADDRESSOF_EXPR);
   MARK_TS_TYPED (PTRMEM_CST);
   MARK_TS_TYPED (EMPTY_CLASS_EXPR);
   MARK_TS_TYPED (VEC_INIT_EXPR);
--- gcc/cp/constexpr.c.jj	2016-10-06 17:46:29.000000000 +0200
+++ gcc/cp/constexpr.c	2016-10-07 09:55:18.395923390 +0200
@@ -5025,6 +5025,11 @@ potential_constant_expression_1 (tree t,
         return (RECUR (from, TREE_CODE (t) != VIEW_CONVERT_EXPR));
       }
 
+    case ADDRESSOF_EXPR:
+      /* This is like ADDR_EXPR, except it won't form pointer-to-member.  */
+      t = TREE_OPERAND (t, 0);
+      goto handle_addr_expr;
+
     case ADDR_EXPR:
       /* -- a unary operator & that is applied to an lvalue that
             designates an object with thread or automatic storage
@@ -5035,6 +5040,7 @@ potential_constant_expression_1 (tree t,
 	/* A pointer-to-member constant.  */
 	return true;
 
+    handle_addr_expr:
 #if 0
       /* FIXME adjust when issue 1197 is fully resolved.  For now don't do
          any checking here, as we might dereference the pointer later.  If
--- gcc/cp/error.c.jj	2016-10-06 17:46:29.000000000 +0200
+++ gcc/cp/error.c	2016-10-07 09:55:18.399923339 +0200
@@ -2678,6 +2678,10 @@ dump_expr (cxx_pretty_printer *pp, tree
       pp_cxx_offsetof_expression (pp, t);
       break;
 
+    case ADDRESSOF_EXPR:
+      pp_cxx_addressof_expression (pp, t);
+      break;
+
     case SCOPE_REF:
       dump_decl (pp, t, flags);
       break;
--- gcc/cp/typeck.c.jj	2016-10-07 09:22:41.000000000 +0200
+++ gcc/cp/typeck.c	2016-10-07 09:55:18.402923302 +0200
@@ -5456,6 +5456,29 @@ build_x_unary_op (location_t loc, enum t
   return exp;
 }
 
+/* Construct and perhaps optimize a tree representation
+   for __builtin_addressof operation.  ARG specifies the operand.  */
+
+tree
+cp_build_addressof (location_t loc, tree arg, tsubst_flags_t complain)
+{
+  tree orig_expr = arg;
+
+  if (processing_template_decl)
+    {
+      if (type_dependent_expression_p (arg))
+	return build_min_nt_loc (loc, ADDRESSOF_EXPR, arg, NULL_TREE);
+
+      arg = build_non_dependent_expr (arg);
+    }
+
+  tree exp = cp_build_addr_expr_strict (arg, complain);
+
+  if (processing_template_decl && exp != error_mark_node)
+    exp = build_min_non_dep (ADDRESSOF_EXPR, exp, orig_expr, NULL_TREE);
+  return exp;
+}
+
 /* Like c_common_truthvalue_conversion, but handle pointer-to-member
    constants, where a null value is represented by an INTEGER_CST of
    -1.  */
--- gcc/cp/cp-tree.h.jj	2016-10-07 09:22:41.124537407 +0200
+++ gcc/cp/cp-tree.h	2016-10-07 09:43:15.705007420 +0200
@@ -6658,6 +6658,8 @@ extern tree build_x_array_ref			(locatio
 extern tree build_x_unary_op			(location_t,
 						 enum tree_code, cp_expr,
                                                  tsubst_flags_t);
+extern tree cp_build_addressof			(location_t, tree,
+						 tsubst_flags_t);
 extern tree cp_build_addr_expr			(tree, tsubst_flags_t);
 extern tree cp_build_unary_op                   (enum tree_code, tree, bool,
                                                  tsubst_flags_t);
--- gcc/cp/cxx-pretty-print.h.jj	2016-10-06 17:46:29.000000000 +0200
+++ gcc/cp/cxx-pretty-print.h	2016-10-07 09:32:00.381501689 +0200
@@ -90,6 +90,7 @@ void pp_cxx_canonical_template_parameter
 void pp_cxx_trait_expression (cxx_pretty_printer *, tree);
 void pp_cxx_va_arg_expression (cxx_pretty_printer *, tree);
 void pp_cxx_offsetof_expression (cxx_pretty_printer *, tree);
+void pp_cxx_addressof_expression (cxx_pretty_printer *, tree);
 void pp_cxx_userdef_literal (cxx_pretty_printer *, tree);
 void pp_cxx_requires_clause (cxx_pretty_printer *, tree);
 void pp_cxx_requires_expr (cxx_pretty_printer *, tree);
--- gcc/cp/cp-tree.def.jj	2016-10-06 17:46:29.000000000 +0200
+++ gcc/cp/cp-tree.def	2016-10-07 09:26:39.947532646 +0200
@@ -334,6 +334,11 @@ DEFTREECODE (TAG_DEFN, "tag_defn", tcc_e
 /* Represents an 'offsetof' expression during template expansion.  */
 DEFTREECODE (OFFSETOF_EXPR, "offsetof_expr", tcc_expression, 1)
 
+/* Represents an '__builtin_addressof' expression during template
+   expansion.  This is similar to ADDR_EXPR, but it doesn't invoke
+   overloaded & operators.  */
+DEFTREECODE (ADDRESSOF_EXPR, "addressof_expr", tcc_expression, 1)
+
 /* Represents the -> operator during template expansion.  */
 DEFTREECODE (ARROW_EXPR, "arrow_expr", tcc_expression, 1)
 
--- gcc/cp/cxx-pretty-print.c.jj	2016-10-06 23:16:43.000000000 +0200
+++ gcc/cp/cxx-pretty-print.c	2016-10-07 09:55:18.406923251 +0200
@@ -380,6 +380,7 @@ pp_cxx_userdef_literal (cxx_pretty_print
    GNU Extensions:
      __builtin_va_arg ( assignment-expression , type-id )
      __builtin_offsetof ( type-id, offsetof-expression )
+     __builtin_addressof ( expression )
 
      __has_nothrow_assign ( type-id )   
      __has_nothrow_constructor ( type-id )
@@ -387,6 +388,7 @@ pp_cxx_userdef_literal (cxx_pretty_print
      __has_trivial_assign ( type-id )   
      __has_trivial_constructor ( type-id )
      __has_trivial_copy ( type-id )
+     __has_unique_object_representations ( type-id )
      __has_trivial_destructor ( type-id )
      __has_virtual_destructor ( type-id )     
      __is_abstract ( type-id )
@@ -456,6 +458,10 @@ cxx_pretty_printer::primary_expression (
       pp_cxx_offsetof_expression (this, t);
       break;
 
+    case ADDRESSOF_EXPR:
+      pp_cxx_addressof_expression (this, t);
+      break;
+
     case REQUIRES_EXPR:
       pp_cxx_requires_expr (this, t);
       break;
@@ -2437,6 +2443,15 @@ pp_cxx_offsetof_expression (cxx_pretty_p
   pp_cxx_right_paren (pp);
 }
 
+void
+pp_cxx_addressof_expression (cxx_pretty_printer *pp, tree t)
+{
+  pp_cxx_ws_string (pp, "__builtin_addressof");
+  pp_cxx_left_paren (pp);
+  pp->expression (TREE_OPERAND (t, 0));
+  pp_cxx_right_paren (pp);
+}
+
 static char const*
 get_fold_operator (tree t)
 {
--- gcc/cp/pt.c.jj	2016-10-06 17:46:29.000000000 +0200
+++ gcc/cp/pt.c	2016-10-07 09:55:51.183511259 +0200
@@ -17204,6 +17204,10 @@ tsubst_copy_and_build (tree t,
       RETURN (finish_offsetof (RECUR (TREE_OPERAND (t, 0)),
 			       EXPR_LOCATION (t)));
 
+    case ADDRESSOF_EXPR:
+      RETURN (cp_build_addressof (EXPR_LOCATION (t),
+				  RECUR (TREE_OPERAND (t, 0)), complain));
+
     case TRAIT_EXPR:
       {
 	tree type1 = tsubst (TRAIT_EXPR_TYPE1 (t), args,
--- gcc/testsuite/g++.dg/cpp0x/addressof1.C.jj	2016-10-07 10:45:09.797113801 +0200
+++ gcc/testsuite/g++.dg/cpp0x/addressof1.C	2016-10-07 11:03:55.376874116 +0200
@@ -0,0 +1,96 @@
+// LWG2296 - addressof should be constexpr
+// { dg-do run { target c++11 } }
+
+template <typename T>
+constexpr inline T *
+addressof (T &x) noexcept
+{
+  return __builtin_addressof (x);
+}
+
+int i;
+static_assert (__builtin_addressof (i) == &i, "");
+static_assert (addressof (i) == &i, "");
+
+constexpr int &j = i;
+static_assert (__builtin_addressof (j) == &i, "");
+static_assert (addressof (j) == &i, "");
+
+struct S { int s; } s;
+static_assert (__builtin_addressof (s) == &s, "");
+static_assert ((int *) __builtin_addressof (s) == &s.s, "");
+static_assert (addressof (s) == &s, "");
+static_assert ((int *) addressof (s) == &s.s, "");
+
+struct T
+{
+  static T tt;
+  constexpr T () : p (addressof (tt)) {}
+  constexpr T *operator & () const { return p; }
+  T *p;
+};
+constexpr T t;
+T T::tt;
+static_assert (__builtin_addressof (t) == (const T *) &t.p, "");
+static_assert (&t == __builtin_addressof (T::tt), "");
+static_assert (addressof (t) == (const T *) &t.p, "");
+static_assert (&t == addressof (T::tt), "");
+
+struct S x, y;
+
+constexpr S *
+foo (bool b)
+{
+  return __builtin_addressof (b ? x : y);
+}
+
+constexpr S *
+bar (bool b, S &c, S &d)
+{
+  return __builtin_addressof (b ? c : d);
+}
+
+static_assert (foo (false) == &y, "");
+static_assert (foo (true) == &x, "");
+static_assert (bar (false, y, x) == &x, "");
+static_assert (bar (true, y, x) == &y, "");
+
+constexpr S *
+foo2 (bool b)
+{
+  return addressof (b ? x : y);
+}
+
+constexpr S *
+bar2 (bool b, S &c, S &d)
+{
+  return addressof (b ? c : d);
+}
+
+static_assert (foo2 (false) == &y, "");
+static_assert (foo2 (true) == &x, "");
+static_assert (bar2 (false, y, x) == &x, "");
+static_assert (bar2 (true, y, x) == &y, "");
+
+constexpr int a = 1;
+static_assert (__builtin_addressof (a) == &a, "");
+static_assert (addressof (a) == &a, "");
+constexpr int c[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
+static_assert ((const int *) __builtin_addressof (c) == &c[0], "");
+static_assert ((const int *) addressof (c) == &c[0], "");
+
+void
+baz ()
+{
+}
+
+int
+main ()
+{
+  if (__builtin_addressof (T::tt) == __builtin_addressof (t)
+      || addressof (T::tt) == addressof (t)
+      || &T::tt != &t
+      || __builtin_addressof (baz) != baz
+      || addressof (baz) != baz)
+    __builtin_abort ();
+}
--- gcc/testsuite/g++.dg/cpp0x/addressof2.C.jj	2016-10-07 11:08:38.481283997 +0200
+++ gcc/testsuite/g++.dg/cpp0x/addressof2.C	2016-10-07 11:08:02.000000000 +0200
@@ -0,0 +1,33 @@
+// LWG2296 - addressof should be constexpr
+// { dg-do compile { target c++11 } }
+
+template <typename T>
+constexpr inline T *
+addressof (T &x) noexcept
+{
+  return __builtin_addressof (x);
+}
+
+auto a = __builtin_addressof (1);		// { dg-error "lvalue required as unary" }
+auto b = addressof (1);				// { dg-error "cannot bind non-const lvalue reference of type" }
+
+struct S { int s : 5; int t; void foo (); } s;
+
+auto c = __builtin_addressof (s);
+auto d = addressof (s);
+auto e = __builtin_addressof (s.s);		// { dg-error "attempt to take address of bit-field structure member" }
+auto f = addressof (s.s);			// { dg-error "cannot bind bitfield" }
+auto g = __builtin_addressof (S{});		// { dg-error "taking address of temporary" }
+auto h = addressof (S{});			// { dg-error "cannot bind non-const lvalue reference of type" }
+auto i = __builtin_addressof (S::t);		// { dg-error "invalid use of non-static data member" }
+auto j = __builtin_addressof (S::foo);		// { dg-error "invalid use of non-static member function" }
+
+void
+foo (bool b)
+{
+  lab:;
+  char c;
+  long long int d;
+  auto k = __builtin_addressof (lab);		// { dg-error "was not declared in this scope" }
+  auto l = __builtin_addressof (b ? c : d);	// { dg-error "lvalue required as unary" }
+}

	Jakub