re PR c++/83116 (Statement with no effect causes wrong code of static object constexpr method)

	PR c++/83116
	* constexpr.c (cxx_eval_call_expression): Only look into
	constexpr_call_table if ctx->strict.

	* g++.dg/cpp1y/constexpr-83116.C: New test.

From-SVN: r255788

gcc/cp/ChangeLog

+2017-12-18  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/83116
+	* constexpr.c (cxx_eval_call_expression): Only look into
+	constexpr_call_table if ctx->strict.
+
 2017-12-18  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/83300

gcc/cp/constexpr.c

@@ -1588,7 +1588,7 @@ cxx_eval_call_expression (const constexpr_ctx *ctx, tree t,
   tree result = NULL_TREE;
 
   constexpr_call *entry = NULL;
-  if (depth_ok && !non_constant_args)
+  if (depth_ok && !non_constant_args && ctx->strict)
     {
       new_call.hash = iterative_hash_template_arg
 	(new_call.bindings, constexpr_fundef_hasher::hash (new_call.fundef));

gcc/testsuite/ChangeLog

+2017-12-18  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/83116
+	* g++.dg/cpp1y/constexpr-83116.C: New test.
+
 2017-12-18  Segher Boessenkool  <segher@kernel.crashing.org>
 
 	PR rtl-optimization/83424

gcc/testsuite/g++.dg/cpp1y/constexpr-83116.C

+// PR c++/83116
+// { dg-do run { target c++14 } }
+// { dg-options "-O2" }
+
+struct S {
+  constexpr S () : s(0) { foo (); }
+  constexpr int foo () { return s; }
+  int s;
+};
+
+int
+main ()
+{
+  static S var;
+  var.s = 5;
+  if (var.s != 5 || var.foo () != 5)
+    __builtin_abort ();
+}