8297689: Fix incorrect result of Short.reverseBytes() call in loops

Reviewed-by: thartmann, jbhateja

src/hotspot/share/opto/vectornode.cpp

@@ -169,10 +169,18 @@ int VectorNode::opcode(int sopc, BasicType bt) {
   case Op_ReverseL:
     return (is_integral_type(bt) ? Op_ReverseV : 0);
   case Op_ReverseBytesS:
-  case Op_ReverseBytesI:
-  case Op_ReverseBytesL:
   case Op_ReverseBytesUS:
-    return (is_integral_type(bt) ? Op_ReverseBytesV : 0);
+    // Subword operations in superword usually don't have precise info
+    // about signedness. But the behavior of reverseBytes for short and
+    // char are exactly the same.
+    return ((bt == T_SHORT || bt == T_CHAR) ? Op_ReverseBytesV : 0);
+  case Op_ReverseBytesI:
+    // There is no reverseBytes() in Byte class but T_BYTE may appear
+    // in VectorAPI calls. We still use ReverseBytesI for T_BYTE to
+    // ensure vector intrinsification succeeds.
+    return ((bt == T_INT || bt == T_BYTE) ? Op_ReverseBytesV : 0);
+  case Op_ReverseBytesL:
+    return (bt == T_LONG ? Op_ReverseBytesV : 0);
   case Op_CompressBits:
     // Not implemented. Returning 0 temporarily
     return 0;

src/hotspot/share/prims/vectorSupport.cpp

@@ -520,8 +520,13 @@ int VectorSupport::vop2ideal(jint id, BasicType bt) {
     }
     case VECTOR_OP_REVERSE_BYTES: {
       switch (bt) {
-        case T_BYTE:
+        case T_SHORT: return Op_ReverseBytesS;
-        case T_SHORT:
+        // Superword requires type consistency between the ReverseBytes*
+        // node and the data. But there's no ReverseBytesB node because
+        // no reverseBytes() method in Java Byte class. T_BYTE can only
+        // appear in VectorAPI calls. We reuse Op_ReverseBytesI for this
+        // to ensure vector intrinsification succeeds.
+        case T_BYTE:  // Intentionally fall-through
         case T_INT:   return Op_ReverseBytesI;
         case T_LONG:  return Op_ReverseBytesL;
         default: fatal("REVERSE_BYTES: %s", type2name(bt));

test/hotspot/jtreg/compiler/vectorization/TestReverseBytes.java

@@ -25,8 +25,7 @@
  * @bug 8288112
  * @summary Auto-vectorization of ReverseBytes operations.
  * @requires vm.compiler2.enabled
- * @requires vm.cpu.features ~= ".*avx2.*"
+ * @requires (os.simpleArch == "x64" & vm.cpu.features ~= ".*avx2.*") | os.simpleArch == "AArch64"
- * @requires os.simpleArch == "x64"
  * @library /test/lib /
  * @run driver compiler.vectorization.TestReverseBytes
  */

test/hotspot/jtreg/compiler/vectorization/TestSubwordReverseBytes.java

@@ -0,0 +1,102 @@
+/*
+ * Copyright (c) 2022, 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.
+ */
+
+package compiler.vectorization;
+
+import compiler.lib.ir_framework.*;
+
+/*
+ * @test
+ * @bug 8297689
+ * @summary Test miscompilation of reverseBytes call from subword types
+ * @library /test/lib /
+ * @requires vm.compiler2.enabled
+ * @run driver compiler.vectorization.TestSubwordReverseBytes
+ */
+
+public class TestSubwordReverseBytes {
+    private static final int SIZE = 32000;
+
+    private static   int[] idx = new int[SIZE];
+    private static short[] rbs = new short[SIZE];
+    private static  char[] rbc = new char[SIZE];
+
+    static {
+        for (int i = 0; i < SIZE; i++) {
+            idx[i] = i;
+        }
+        for (short s = 0; s < SIZE; s++) {
+            rbs[s] = Short.reverseBytes(s);
+        }
+        for (char c = 0; c < SIZE; c++) {
+            rbc[c] = Character.reverseBytes(c);
+        }
+    }
+
+    @Test
+    @IR(failOn = {IRNode.REVERSE_BYTES_V})
+    public static int[] testShortReverseBytes() {
+        int[] res = new int[SIZE];
+        for (int i = 0; i < SIZE; i++) {
+           res[i] = Short.reverseBytes((short) idx[i]);
+        }
+        return res;
+    }
+
+    @Run(test = "testShortReverseBytes")
+    public static void testShort() {
+        int[] res = testShortReverseBytes();
+        for (int i = 0; i < SIZE; i++) {
+            if (res[i] != rbs[i]) {
+                throw new RuntimeException("Wrong result: expected = " +
+                        (int) rbs[i] + ", actual = " + res[i]);
+            }
+        }
+    }
+
+    @Test
+    @IR(failOn = {IRNode.REVERSE_BYTES_V})
+    public static int[] testCharacterReverseBytes() {
+        int[] res = new int[SIZE];
+        for (int i = 0; i < SIZE; i++) {
+           res[i] = Character.reverseBytes((char) idx[i]);
+        }
+        return res;
+    }
+
+    @Run(test = "testCharacterReverseBytes")
+    public static void testChar() {
+        int[] res = testCharacterReverseBytes();
+        for (int i = 0; i < SIZE; i++) {
+            if (res[i] != rbc[i]) {
+                throw new RuntimeException("Wrong result: expected = " +
+                        (int) rbc[i] + ", actual = " + res[i]);
+            }
+        }
+    }
+
+    public static void main(String[] args) {
+        TestFramework.run();
+    }
+}
+

test/hotspot/jtreg/compiler/vectorization/runner/BasicCharOpTest.java

@@ -47,15 +47,18 @@ public class BasicCharOpTest extends VectorizationTestRunner {
     private char[] a;
     private char[] b;
     private char[] c;
+    private int[] idx;
 
     public BasicCharOpTest() {
         a = new char[SIZE];
         b = new char[SIZE];
         c = new char[SIZE];
+        idx = new int[SIZE];
         for (int i = 0; i < SIZE; i++) {
             a[i] = (char) (20 * i);
             b[i] = (char) (i + 44444);
             c[i] = (char) 10000;
+            idx[i] = i;
         }
     }
 
@@ -189,5 +192,24 @@ public class BasicCharOpTest extends VectorizationTestRunner {
         }
         return res;
     }
+
+    // ------------- ReverseBytes -------------
+    @Test
+    public char[] reverseBytesWithChar() {
+        char[] res = new char[SIZE];
+        for (int i = 0; i < SIZE; i++) {
+            res[i] = Character.reverseBytes(a[i]);
+        }
+        return res;
+    }
+
+    @Test
+    public int[] reverseBytesWithInt() {
+        int[] res = new int[SIZE];
+        for (int i = 0; i < SIZE; i++) {
+            res[i] = Character.reverseBytes((char) idx[i]);
+        }
+        return res;
+    }
 }
 

test/hotspot/jtreg/compiler/vectorization/runner/BasicShortOpTest.java

@@ -47,15 +47,18 @@ public class BasicShortOpTest extends VectorizationTestRunner {
     private short[] a;
     private short[] b;
     private short[] c;
+    private int[] idx;
 
     public BasicShortOpTest() {
         a = new short[SIZE];
         b = new short[SIZE];
         c = new short[SIZE];
+        idx = new int[SIZE];
         for (int i = 0; i < SIZE; i++) {
             a[i] = (short) (-12 * i);
             b[i] = (short) (9 * i + 8888);
             c[i] = (short) -32323;
+            idx[i] = i;
         }
     }
 
@@ -187,5 +190,24 @@ public class BasicShortOpTest extends VectorizationTestRunner {
         }
         return res;
     }
+
+    // ------------- ReverseBytes -------------
+    @Test
+    public short[] reverseBytesWithShort() {
+        short[] res = new short[SIZE];
+        for (int i = 0; i < SIZE; i++) {
+            res[i] = Short.reverseBytes(a[i]);
+        }
+        return res;
+    }
+
+    @Test
+    public int[] reverseBytesWithInt() {
+        int[] res = new int[SIZE];
+        for (int i = 0; i < SIZE; i++) {
+            res[i] = Short.reverseBytes((short) idx[i]);
+        }
+        return res;
+    }
 }