re PR c++/3698 (improper handling of an extern declared inline function)

	PR c++/3698
	PR c++/86208
	* cp-gimplify.c (cp_genericize_r): When using extern_decl_map, or
	in TREE_USED flag from stmt to h->to.

	* g++.dg/opt/pr3698.C: New test.

From-SVN: r262678

gcc/cp/ChangeLog

+2018-07-16  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/3698
+	PR c++/86208
+	* cp-gimplify.c (cp_genericize_r): When using extern_decl_map, or
+	in TREE_USED flag from stmt to h->to.
+
 2018-07-13  Nathan Sidwell  <nathan@acm.org>
 
 	PR c++/86374

gcc/cp/cp-gimplify.c

@@ -1085,6 +1085,7 @@ cp_genericize_r (tree *stmt_p, int *walk_subtrees, void *data)
       if (h)
 	{
 	  *stmt_p = h->to;
+	  TREE_USED (h->to) |= TREE_USED (stmt);
 	  *walk_subtrees = 0;
 	  return NULL;
 	}

gcc/testsuite/ChangeLog

+2018-07-16  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/3698
+	PR c++/86208
+	* g++.dg/opt/pr3698.C: New test.
+
 2018-07-16  Richard Biener  <rguenther@suse.de>
 
 	PR ipa/86389

gcc/testsuite/g++.dg/opt/pr3698.C

+// PR c++/3698
+// { dg-do link }
+// { dg-options "-O0" }
+
+struct X {
+  int i;
+};
+
+inline const int&
+OHashKey (const X& x)
+{
+  return x.i;
+}
+
+int
+main ()
+{
+ extern const int& OHashKey (const X& x);
+ X x;
+ return OHashKey (x);
+}