--- a/src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp	Mon May 20 14:19:19 2019 -0700
+++ b/src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp	Wed May 22 20:12:19 2019 +0300
@@ -4338,6 +4338,7 @@
     __ ldr(ch1, Address(str1));
     // Read whole register from str2. It is safe, because length >=8 here
     __ ldr(ch2, Address(str2));
+    __ sub(cnt2, cnt2, cnt1);
     __ andr(first, ch1, str1_isL ? 0xFF : 0xFFFF);
     if (str1_isL != str2_isL) {
       __ eor(v0, __ T16B, v0, v0);

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/hotspot/jtreg/compiler/intrinsics/Test8215792.java	Wed May 22 20:12:19 2019 +0300
@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2019, Arm Limited. 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 8215792
+ * @summary Fix a bug in AArch64 string intrinsics
+ *
+ * @run main/othervm compiler.intrinsics.Test8215792
+ * @run main/othervm -XX:-CompactStrings compiler.intrinsics.Test8215792
+ */
+
+package compiler.intrinsics;
+
+public class Test8215792 {
+
+    private static final int ITERATIONS = 10000;
+    private static final String pattern = "01234567890123456789";
+
+    public static void main(String[] args) {
+
+        // Repeat many times to trigger compilation
+        for (int iter = 0; iter < ITERATIONS; iter++) {
+            StringBuilder str1 = new StringBuilder("ABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890123456789");
+            StringBuilder str2 = new StringBuilder("\u4f60\u598dCDEFGHIJKLMNOPQRSTUVWXYZ01234567890123456789");
+
+            for (int i = 0; i < 20; i++) {
+                // Remove one character from the tail
+                str1.setLength(str1.length() - 1);
+                str2.setLength(str2.length() - 1);
+                // Pattern string should not be found after characters removed from the tail
+                if (str1.indexOf(pattern) != -1 || str2.indexOf(pattern) != -1) {
+                    System.out.println("FAILED");
+                    System.exit(1);
+                }
+            }
+        }
+        System.out.println("PASSED");
+    }
+}
+