re PR c++/78550 (bit field and std::initializer_list)

	PR c++/78550
	* convert.c (convert_to_integer_1): Maybe fold conversions to
	integral types with fewer bits than its mode.

	testsuite/
	PR c++/78550
	* g++.dg/cpp1y/pr78550.C: New.

From-SVN: r243479

gcc/ChangeLog

+2016-12-09  Nathan Sidwell  <nathan@acm.org>
+
+	PR C++/78550
+	* convert.c (convert_to_integer_1): Maybe fold conversions to
+	integral types with fewer bits than its mode.
+
 2016-12-09  Martin Liska  <mliska@suse.cz>
 
 	* tree-pretty-print.c (pretty_print_string): Escape non-printable
@@ -67,9 +73,8 @@
 
 2016-12-08  Dmitry Vyukov  <dvyukov@google.com>
 
-	* opts.c (finish_options): Enable
-	-fsanitize-address-use-after-scope only if -fsanitize=address is enabled
-	(not -fsanitize=kernel-address).
+	* opts.c (finish_options): Enable -fsanitize-address-use-after-scope
+	only if -fsanitize=address is enabled (not -fsanitize=kernel-address).
 	* doc/invoke.texi (-fsanitize=kernel-address):
 	Don't say that it enables -fsanitize-address-use-after-scope.
 

gcc/convert.c

@@ -646,10 +646,11 @@ convert_to_integer_1 (tree type, tree expr, bool dofold)
 	 to TYPE.  */
       else if (TREE_CODE (type) == ENUMERAL_TYPE
 	       || outprec != GET_MODE_PRECISION (TYPE_MODE (type)))
-	return build1 (NOP_EXPR, type,
-		       convert (lang_hooks.types.type_for_mode
-				(TYPE_MODE (type), TYPE_UNSIGNED (type)),
-				expr));
+	{
+	  expr = convert (lang_hooks.types.type_for_mode
+			  (TYPE_MODE (type), TYPE_UNSIGNED (type)), expr);
+	  return maybe_fold_build1_loc (dofold, loc, NOP_EXPR, type, expr);
+	}
 
       /* Here detect when we can distribute the truncation down past some
 	 arithmetic.  For example, if adding two longs and converting to an

gcc/testsuite/ChangeLog

+2016-12-09  Nathan Sidwell  <nathan@acm.org>
+
+	PR c++/78550
+	* g++.dg/cpp1y/pr78550.C: New.
+
 2016-12-09  Paul Thomas  <pault@gcc.gnu.org>
 
 	PR fortran/44265

gcc/testsuite/g++.dg/cpp1y/pr78550.C

+// { dg-do compile { target c++14 } }
+
+// PR 78550 ICE with initializer_list and bitfield member
+
+namespace std
+{
+  template <class T>
+  struct initializer_list
+    {
+      const T *a;
+      __SIZE_TYPE__ b;
+      constexpr initializer_list (const T *x, __SIZE_TYPE__ y) : a(x), b(y) { }
+    };
+}
+template <typename T>
+struct A {
+  A (std::initializer_list<T>);
+};
+struct B {
+  int k : 1;
+};
+A<B> a{{0}};