8058847: C2: EliminateAutoBox regression after 8042786

Reviewed-by: kvn, roland

hotspot/src/share/vm/opto/memnode.cpp

@@ -1257,6 +1257,16 @@ Node* LoadNode::eliminate_autobox(PhaseGVN* phase) {
               result = new ConvI2LNode(phase->transform(result));
             }
 #endif
+            // Boxing/unboxing can be done from signed & unsigned loads (e.g. LoadUB -> ... -> LoadB pair).
+            // Need to preserve unboxing load type if it is unsigned.
+            switch(this->Opcode()) {
+              case Op_LoadUB:
+                result = new AndINode(phase->transform(result), phase->intcon(0xFF));
+                break;
+              case Op_LoadUS:
+                result = new AndINode(phase->transform(result), phase->intcon(0xFFFF));
+                break;
+            }
             return result;
           }
         }

hotspot/test/compiler/EliminateAutoBox/UnsignedLoads.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright (c) 2014, 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.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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
+ * @library /testlibrary
+ * @run main/othervm -Xbatch -XX:+EliminateAutoBox
+ *                   -XX:CompileOnly=::valueOf,::byteValue,::shortValue,::testUnsignedByte,::testUnsignedShort
+ *                   UnsignedLoads
+ */
+import static com.oracle.java.testlibrary.Asserts.assertEQ;
+
+public class UnsignedLoads {
+    public static int testUnsignedByte() {
+        byte[] bytes = new byte[] {-1};
+        int res = 0;
+        for (int i = 0; i < 100000; i++) {
+            for (Byte b : bytes) {
+                res = b & 0xff;
+            }
+        }
+        return res;
+    }
+
+    public static int testUnsignedShort() {
+        int res = 0;
+        short[] shorts = new short[] {-1};
+        for (int i = 0; i < 100000; i++) {
+            for (Short s : shorts) {
+                res = s & 0xffff;
+            }
+        }
+        return res;
+    }
+
+    public static void main(String[] args) {
+        assertEQ(testUnsignedByte(),    255);
+        assertEQ(testUnsignedShort(), 65535);
+        System.out.println("TEST PASSED");
+    }
+}