re PR c++/78949 (incorrect "unused variable" warning with SSE2)

	PR c++/78949
	* typeck.c (cp_build_unary_op): Call mark_rvalue_use on arg if it has
	vector type.

	* c-c++-common/Wunused-var-16.c: New test.

From-SVN: r244075

gcc/cp/ChangeLog

 2017-01-04  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/78949
+	* typeck.c (cp_build_unary_op): Call mark_rvalue_use on arg if it has
+	vector type.
+
 	PR c++/78693
 	* parser.c (cp_parser_simple_declaration): Only complain about
 	inconsistent auto deduction if auto_result doesn't use auto.

gcc/cp/typeck.c

@@ -5907,6 +5907,8 @@ cp_build_unary_op (enum tree_code code, tree xarg, bool noconvert,
 	    inform (location, "did you mean to use logical not (%<!%>)?");
 	  arg = cp_perform_integral_promotions (arg, complain);
 	}
+      else if (!noconvert && VECTOR_TYPE_P (TREE_TYPE (arg)))
+	arg = mark_rvalue_use (arg);
       break;
 
     case ABS_EXPR:

gcc/testsuite/ChangeLog

 2017-01-04  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/78949
+	* c-c++-common/Wunused-var-16.c: New test.
+
 	PR c++/78693
 	* g++.dg/cpp0x/pr78693.C: New test.
 

gcc/testsuite/c-c++-common/Wunused-var-16.c

+/* PR c++/78949 */
+/* { dg-do compile } */
+/* { dg-options "-Wunused" } */
+
+typedef unsigned char V __attribute__((vector_size(16)));
+V v;
+
+void
+foo ()
+{
+  V y = {};
+  V x = {};	// { dg-bogus "set but not used" }
+  y &= ~x;
+  v = y;
+}