cp-gimplify.c (cp_maybe_instrument_return): Don't add __builtin_unreachable if…

cp-gimplify.c (cp_maybe_instrument_return): Don't add __builtin_unreachable if -O0 or if -fsanitize=unreachable.

	* cp-gimplify.c (cp_maybe_instrument_return): Don't add
	__builtin_unreachable if -O0 or if -fsanitize=unreachable.

	* g++.dg/missing-return.C: Add -O to dg-options.

From-SVN: r255403

gcc/cp/ChangeLog

+2017-12-05  Jakub Jelinek  <jakub@redhat.com>
+
+	* cp-gimplify.c (cp_maybe_instrument_return): Don't add
+	__builtin_unreachable if -O0 or if -fsanitize=unreachable.
+
 2017-12-04  Jason Merrill  <jason@redhat.com>
 
 	PR c++/83273 - constexpr if allows non-constant condition

gcc/cp/cp-gimplify.c

@@ -1554,6 +1554,18 @@ cp_maybe_instrument_return (tree fndecl)
       || !targetm.warn_func_return (fndecl))
     return;
 
+  if (!sanitize_flags_p (SANITIZE_RETURN, fndecl)
+      /* Don't add __builtin_unreachable () if not optimizing, it will not
+	 improve any optimizations in that case, just break UB code.
+	 Don't add it if -fsanitize=unreachable -fno-sanitize=return either,
+	 UBSan covers this with ubsan_instrument_return above where sufficient
+	 information is provided, while the __builtin_unreachable () below
+	 if return sanitization is disabled will just result in hard to
+	 understand runtime error without location.  */
+      && (!optimize
+	  || sanitize_flags_p (SANITIZE_UNREACHABLE, fndecl)))
+    return;
+
   tree t = DECL_SAVED_TREE (fndecl);
   while (t)
     {

gcc/testsuite/ChangeLog

+2017-12-05  Jakub Jelinek  <jakub@redhat.com>
+
+	* g++.dg/missing-return.C: Add -O to dg-options.
+
 2017-12-04  Jeff Law  <law@redhat.com>
 
 	PR tree-optimization/78496

gcc/testsuite/g++.dg/missing-return.C

 /* { dg-do compile } */
-/* { dg-options "-Wreturn-type -fdump-tree-optimized" } */
+/* { dg-options "-Wreturn-type -fdump-tree-optimized -O" } */
 
 int foo(int a)
 {