--- a/hotspot/src/cpu/sparc/vm/sparc.ad	Fri Nov 01 08:35:58 2013 -0700
+++ b/hotspot/src/cpu/sparc/vm/sparc.ad	Mon Nov 04 21:59:54 2013 +0100
@@ -2916,6 +2916,9 @@
       __ bind(LSkip2);
     }
 
+    // We have no guarantee that on 64 bit the higher half of limit_reg is 0
+    __ signx(limit_reg);
+
     __ subcc(limit_reg, 1 * sizeof(jchar), chr1_reg);
     __ br(Assembler::equal, true, Assembler::pn, Ldone);
     __ delayed()->mov(O7, result_reg);  // result is difference in lengths
@@ -2973,6 +2976,9 @@
     Register  chr1_reg = result_reg;
     Register  chr2_reg =   tmp1_reg;
 
+    // We have no guarantee that on 64 bit the higher half of limit_reg is 0
+    __ signx(limit_reg);
+
     //check for alignment and position the pointers to the ends
     __ or3(str1_reg, str2_reg, chr1_reg);
     __ andcc(chr1_reg, 0x3, chr1_reg);

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/test/compiler/intrinsics/stringequals/TestStringEqualsBadLength.java	Mon Nov 04 21:59:54 2013 +0100
@@ -0,0 +1,82 @@
+/*
+ * Copyright (c) 2013, 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 8027445
+ * @summary String.equals() may be called with a length whose upper bits are not cleared
+ * @run main/othervm -XX:-UseOnStackReplacement -XX:-BackgroundCompilation TestStringEqualsBadLength
+ *
+ */
+
+import java.util.Arrays;
+
+public class TestStringEqualsBadLength {
+
+    int v1;
+    int v2;
+
+    boolean m(String s1) {
+        int l = v2 - v1; // 0 - (-1) = 1. On 64 bit: 0xffffffff00000001
+        char[] arr = new char[l];
+        arr[0] = 'a';
+        String s2 = new String(arr);
+        // The string length is not reloaded but the value computed is
+        // reused so pointer computation must not use
+        // 0xffffffff00000001
+        return s2.equals(s1);
+    }
+
+    // Same thing with String.compareTo()
+    int m2(String s1) {
+        int l = v2 - v1;
+        char[] arr = new char[l+1];
+        arr[0] = 'a';
+        arr[1] = 'b';
+        String s2 = new String(arr);
+        return s2.compareTo(s1);
+    }
+
+    // Same thing with equals() for arrays
+    boolean m3(char[] arr1) {
+        int l = v2 - v1; // 0 - (-1) = 1. On 64 bit: 0xffffffff00000001
+        char[] arr2 = new char[l];
+        arr2[0] = 'a';
+        return Arrays.equals(arr2, arr1);
+    }
+
+    static public void main(String[] args) {
+        TestStringEqualsBadLength tse = new TestStringEqualsBadLength();
+        tse.v1 = -1;
+        tse.v2 = 0;
+        char[] arr = new char[1];
+        arr[0] = 'a';
+        for (int i = 0; i < 20000; i++) {
+            tse.m("a");
+            tse.m2("ab");
+            tse.m3(arr);
+        }
+
+        System.out.println("TEST PASSED");
+    }
+}