8231058: VerifyOops crashes with assert(_offset >= 0) failed: offset for non comment?

Offset method should only be called for comments.

Backport-of: 6bc9833

Author: SendaoYan

src/hotspot/share/asm/codeBuffer.cpp

@@ -1100,7 +1100,7 @@ CodeString* CodeStrings::find(intptr_t offset) const {
 // Convenience for add_comment.
 CodeString* CodeStrings::find_last(intptr_t offset) const {
   CodeString* a = _strings_last;
-  while (a != NULL && !a->is_comment() && a->offset() > offset) {
+  while (a != NULL && !(a->is_comment() && a->offset() == offset)) {
     a = a->_prev;
   }
   return a;

test/hotspot/jtreg/runtime/CheckUnhandledOops/TestVerifyOops.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8231058
+ * @requires vm.debug & (os.arch != "sparc") & (os.arch != "sparcv9")
+ * @run main/othervm -XX:+VerifyOops TestVerifyOops
+ */
+
+public class TestVerifyOops {
+
+    public static void main(String[] args) {
+        System.out.println("Test passed");
+    }
+}